| Age | Commit message (Collapse) | Author | Files | Lines |
|---|
|
The root argument for btrfs_update_inode() always matches the root of the
given inode, so remove the root argument and get it from the inode
argument.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
In later patches, we're going to change how the inode's ctime field is
used. Switch to using accessor functions instead of raw accesses of
inode->i_ctime.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Message-Id: <20230705190309.579783-27-jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
|
The function is for internal interfaces so we should use the
btrfs_inode.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
The function is for internal interfaces so we should use the
btrfs_inode.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
This will make syncing fs.h to user space a little easier if we can pull
the super block specific helpers out of fs.h and put them in super.h.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
Move these out of ctree.h into file.h to cut down on code in ctree.h.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
Move these prototypes out of ctree.h and into file-item.h.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
Update, reformat or reword function comments. This also removes the kdoc
marker so we don't get reports when the function name is missing.
Changes made:
- remove kdoc markers
- reformat the brief description to be a proper sentence
- reword to imperative voice
- align parameter list
- fix typos
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
This is a large patch, but because they're all macros it's impossible to
split up. Simply copy all of the item accessors in ctree.h and paste
them in accessors.h, and then update any files to include the header so
everything compiles.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ reformat comments, style fixups ]
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
We're going to use fs.h to hold fs wide related helpers and definitions,
move the FS_STATE enum and related helpers to fs.h, and then update all
files that need these definitions to include fs.h.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
We have a bunch of printk helpers that are in ctree.h. These have
nothing to do with ctree.c, so move them into their own header.
Subsequent patches will cleanup the printk helpers.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
Instead of taking up a whole argument to indicate we're clearing
everything in a range, simply add another EXTENT bit to control this,
and then update all the callers to drop this argument from the
clear_extent_bit variants.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
We have two variants of lock/unlock extent, one set that takes a cached
state, another that does not. This is slightly annoying, and generally
speaking there are only a few places where we don't have a cached state.
Simplify this by making lock_extent/unlock_extent the only variant and
make it take a cached state, then convert all the callers appropriately.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
This is only used in the case that we are clearing EXTENT_LOCKED, so
infer this value from the bits passed in instead of taking it as an
argument.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
The chained assignments may be convenient to write, but make readability
a bit worse as it's too easy to overlook that there are several values
set on the same line while this is rather an exception. Making it
consistent everywhere avoids surprises.
The pattern where inode times are initialized reuses the first value and
the order is mtime, ctime. In other blocks the assignments are expanded
so the order of variables is similar to the neighboring code.
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
When reflinking extents (clone and deduplication), we need to touch the
btree of the destination inode's subvolume, as well as potentially
create a delayed inode for the destination inode (if it was not created
before). However we are neither balancing the btree dirty pages nor the
delayed items after such operations, so if we have a task that is doing
a long series of clone or deduplication operations, it can result in
accumulation of too many btree dirty pages and delayed items.
So just call btrfs_btree_balance_dirty() after clone and deduplication,
just like we do for every other system call that results on modifying a
btree and adding delayed items.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
Both memzero_page and memcpy_to_page already call flush_dcache_page so
we can remove the calls from btrfs code.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
When replacing file extents, called during fallocate, hole punching,
clone and deduplication, we may not be able to replace/drop all the
target file extent items with a single transaction handle. We may get
-ENOSPC while doing it, in which case we release the transaction handle,
balance the dirty pages of the btree inode, flush delayed items and get
a new transaction handle to operate on what's left of the target range.
By dropping and replacing file extent items we have effectively modified
the inode, so we should bump its iversion and update its mtime/ctime
before we update the inode item. This is because if the transaction
we used for partially modifying the inode gets committed by someone after
we release it and before we finish the rest of the range, a power failure
happens, then after mounting the filesystem our inode has an outdated
iversion and mtime/ctime, corresponding to the values it had before we
changed it.
So add the missing iversion and mtime/ctime updates.
Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
While doing a reflink operation, if an ordered extent for a file range
that does not overlap with the source and destination ranges of the
reflink operation happens, we can end up having a failure in the reflink
operation and return -EINVAL to user space.
The following sequence of steps explains how this can happen:
1) We have the page at file offset 315392 dirty (under delalloc);
2) A reflink operation for this file starts, using the same file as both
source and destination, the source range is [372736, 409600) (length of
36864 bytes) and the destination range is [208896, 245760);
3) At btrfs_remap_file_range_prep(), we flush all delalloc in the source
and destination ranges, and wait for any ordered extents in those range
to complete;
4) Still at btrfs_remap_file_range_prep(), we then flush all delalloc in
the inode, but we neither wait for it to complete nor any ordered
extents to complete. This results in starting delalloc for the page at
file offset 315392 and creating an ordered extent for that single page
range;
5) We then move to btrfs_clone() and enter the loop to find file extent
items to copy from the source range to destination range;
6) In the first iteration we end up at last file extent item stored in
leaf A:
(...)
item 131 key (143616 108 315392) itemoff 5101 itemsize 53
extent data disk bytenr 1903988736 nr 73728
extent data offset 12288 nr 61440 ram 73728
This represents the file range [315392, 376832), which overlaps with
the source range to clone.
@datal is set to 61440, key.offset is 315392 and @next_key_min_offset
is therefore set to 376832 (315392 + 61440).
@off (372736) is > key.offset (315392), so @new_key.offset is set to
the value of @destoff (208896).
@new_key.offset == @last_dest_end (208896) so @drop_start is set to
208896 (@new_key.offset).
@datal is adjusted to 4096, as @off is > @key.offset.
So in this iteration we call btrfs_replace_file_extents() for the range
[208896, 212991] (a single page, which is
[@drop_start, @new_key.offset + @datal - 1]).
@last_dest_end is set to 212992 (@new_key.offset + @datal =
208896 + 4096 = 212992).
Before the next iteration of the loop, @key.offset is set to the value
376832, which is @next_key_min_offset;
7) On the second iteration btrfs_search_slot() leaves us again at leaf A,
but this time pointing beyond the last slot of leaf A, as that's where
a key with offset 376832 should be at if it existed. So end up calling
btrfs_next_leaf();
8) btrfs_next_leaf() releases the path, but before it searches again the
tree for the next key/leaf, the ordered extent for the single page
range at file offset 315392 completes. That results in trimming the
file extent item we processed before, adjusting its key offset from
315392 to 319488, reducing its length from 61440 to 57344 and inserting
a new file extent item for that single page range, with a key offset of
315392 and a length of 4096.
Leaf A now looks like:
(...)
item 132 key (143616 108 315392) itemoff 4995 itemsize 53
extent data disk bytenr 1801666560 nr 4096
extent data offset 0 nr 4096 ram 4096
item 133 key (143616 108 319488) itemoff 4942 itemsize 53
extent data disk bytenr 1903988736 nr 73728
extent data offset 16384 nr 57344 ram 73728
9) When btrfs_next_leaf() returns, it gives us a path pointing to leaf A
at slot 133, since it's the first key that follows what was the last
key we saw (143616 108 315392). In fact it's the same item we processed
before, but its key offset was changed, so it counts as a new key;
10) So now we have:
@key.offset == 319488
@datal == 57344
@off (372736) is > key.offset (319488), so @new_key.offset is set to
208896 (@destoff value).
@new_key.offset (208896) != @last_dest_end (212992), so @drop_start
is set to 212992 (@last_dest_end value).
@datal is adjusted to 4096 because @off > @key.offset.
So in this iteration we call btrfs_replace_file_extents() for the
invalid range of [212992, 212991] (which is
[@drop_start, @new_key.offset + @datal - 1]).
This range is empty, the end offset is smaller than the start offset
so btrfs_replace_file_extents() returns -EINVAL, which we end up
returning to user space and fail the reflink operation.
This all happens because the range of this file extent item was
already processed in the previous iteration.
This scenario can be triggered very sporadically by fsx from fstests, for
example with test case generic/522.
So fix this by having btrfs_clone() skip file extent items that cover a
file range that we have already processed.
CC: stable@vger.kernel.org # 5.10+
Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
We have four different scenarios where we don't expect to find ordered
extents after locking a file range:
1) During plain fallocate;
2) During hole punching;
3) During zero range;
4) During reflinks (both cloning and deduplication).
This is because in all these cases we follow the pattern:
1) Lock the inode's VFS lock in exclusive mode;
2) Lock the inode's i_mmap_lock in exclusive node, to serialize with
mmap writes;
3) Flush delalloc in a file range and wait for all ordered extents
to complete - both done through btrfs_wait_ordered_range();
4) Lock the file range in the inode's io_tree.
So add a helper that asserts that we don't have ordered extents for a
given range. Make the four scenarios listed above use this helper after
locking the respective file range.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
When starting a reflink operation we have these calls to inode_dio_wait()
which used to be needed because direct IO writes that don't cross the
i_size boundary did not take the inode's VFS lock, so we could race with
them and end up with ordered extents in target range after calling
btrfs_wait_ordered_range().
However that is not the case anymore, because the inode's VFS lock was
changed from a mutex to a rw semaphore, by commit 9902af79c01a8e
("parallel lookups: actual switch to rwsem"), and several years later we
started to lock the inode's VFS lock in shared mode for direct IO writes
that don't cross the i_size boundary (commit e9adabb9712ef9 ("btrfs: use
shared lock for direct writes within EOF")).
So remove those inode_dio_wait() calls.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
All filesystems have now been converted to use ->readahead, so
remove the ->readpages operation and fix all the comments that
used to refer to it.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
The sb check is already done in do_clone_file_range, and the mnt check
(which will hopefully go away in a subsequent patch) is done in
ioctl_file_clone(). Remove the check in our code and put an ASSERT() to
make sure it doesn't change underneath us.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
Smatch complains about a possible dereference of a pointer that was not
initialized:
CC [M] fs/btrfs/reflink.o
CHECK fs/btrfs/reflink.c
fs/btrfs/reflink.c:533 btrfs_clone() error: potentially dereferencing uninitialized 'trans'.
This is because we are not dealing with the case where the type of a file
extent has an unexpected value (not regular, not prealloc and not inline),
in which case the transaction handle pointer is not initialized.
Such unexpected type should be impossible, except in case of some memory
corruption caused either by bad hardware or some software bug causing
something like a buffer overrun.
So ASSERT that if the extent type is neither regular nor prealloc, then
it must be inline. Bail out with -EUCLEAN and a warning in case it is
not. This silences smatch.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
When reflinking an inline extent, we assert that its file offset is 0 and
that its uncompressed length is not greater than the sector size. We then
return an error if one of those conditions is not satisfied. However we
use a return statement, which results in returning from btrfs_clone()
without freeing the path and buffer that were allocated before, as well as
not clearing the flag BTRFS_INODE_NO_DELALLOC_FLUSH for the destination
inode.
Fix that by jumping to the 'out' label instead, and also add a WARN_ON()
for each condition so that in case assertions are disabled, we get to
known which of the unexpected conditions triggered the error.
Fixes: a61e1e0df9f321 ("Btrfs: simplify inline extent handling when doing reflinks")
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
When an inode has a last_reflink_trans matching the current transaction,
we have to take special care when logging its checksums in order to
avoid getting checksum items with overlapping ranges in a log tree,
which could result in missing checksums after log replay (more on that
in the changelogs of commit 40e046acbd2f36 ("Btrfs: fix missing data
checksums after replaying a log tree") and commit e289f03ea79bbc ("btrfs:
fix corrupt log due to concurrent fsync of inodes with shared extents")).
We also need to make sure a full fsync will copy all old file extent
items it finds in modified leaves, because they might have been copied
from some other inode.
However once we fsync an inode, we don't need to keep paying the price of
that extra special care in future fsyncs done in the same transaction,
unless the inode is used for another reflink operation or the full sync
flag is set on it (truncate, failure to allocate extent maps for holes,
and other exceptional and infrequent cases).
So after we fsync an inode reset its last_unlink_trans to zero. In case
another reflink happens, we continue to update the last_reflink_trans of
the inode, just as before. Also set last_reflink_trans to the generation
of the last transaction that modified the inode whenever we need to set
the full sync flag on the inode, just like when we need to load an inode
from disk after eviction.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
When logging an inode in full sync mode, we go over every leaf that was
modified in the current transaction and has items associated to our inode,
and then copy all those items into the log tree. This includes copying
file extent items that were created and added to the inode in past
transactions, which is useless and only makes use more leaf space in the
log tree.
It's common to have a file with many file extent items spanning many
leaves where only a few file extent items are new and need to be logged,
and in such case we log all the file extent items we find in the modified
leaves.
So change the full sync behaviour to skip over file extent items that are
not needed. Those are the ones that match the following criteria:
1) Have a generation older than the current transaction and the inode
was not a target of a reflink operation, as that can copy file extent
items from a past generation from some other inode into our inode, so
we have to log them;
2) Start at an offset within i_size - we must log anything at or beyond
i_size, otherwise we would lose prealloc extents after log replay.
The following script exercises a scenario where this happens, and it's
somehow close enough to what happened often on a SQL Server workload which
I had to debug sometime ago to fix an issue where a pattern of writes to
prealloc extents and fsync resulted in fsync failing with -EIO (that was
commit ea7036de0d36c4 ("btrfs: fix fsync failure and transaction abort
after writes to prealloc extents")). In that particular case, we had large
files that had random writes and were often truncated, which made the
next fsync be a full sync.
$ cat test.sh
#!/bin/bash
DEV=/dev/sdi
MNT=/mnt/sdi
MKFS_OPTIONS="-O no-holes -R free-space-tree"
MOUNT_OPTIONS="-o ssd"
FILE_SIZE=$((1 * 1024 * 1024 * 1024)) # 1G
# FILE_SIZE=$((2 * 1024 * 1024 * 1024)) # 2G
# FILE_SIZE=$((512 * 1024 * 1024)) # 512M
mkfs.btrfs -f $MKFS_OPTIONS $DEV
mount $MOUNT_OPTIONS $DEV $MNT
# Create a file with many extents. Use direct IO to make it faster
# to create the file - using buffered IO we would have to fsync
# after each write (terribly slow).
echo "Creating file with $((FILE_SIZE / 4096)) extents of 4K each..."
xfs_io -f -d -c "pwrite -b 4K 0 $FILE_SIZE" $MNT/foobar
# Commit the transaction, so every extent after this is from an
# old generation.
sync
# Now rewrite only a few extents, which are all far spread apart from
# each other (e.g. 1G / 32M = 32 extents).
# After this only a few extents have a new generation, while all other
# ones have an old generation.
echo "Rewriting $((FILE_SIZE / (32 * 1024 * 1024))) extents..."
for ((i = 0; i < $FILE_SIZE; i += $((32 * 1024 * 1024)))); do
xfs_io -c "pwrite $i 4K" $MNT/foobar >/dev/null
done
# Fsync, the inode logged in full sync mode since it was never fsynced
# before.
echo "Fsyncing file..."
xfs_io -c "fsync" $MNT/foobar
umount $MNT
And the following bpftrace program was running when executing the test
script:
$ cat bpf-script.sh
#!/usr/bin/bpftrace
k:btrfs_log_inode
{
@start_log_inode[tid] = nsecs;
}
kr:btrfs_log_inode
/@start_log_inode[tid]/
{
@log_inode_dur[tid] = (nsecs - @start_log_inode[tid]) / 1000;
delete(@start_log_inode[tid]);
}
k:btrfs_sync_log
{
@start_sync_log[tid] = nsecs;
}
kr:btrfs_sync_log
/@start_sync_log[tid]/
{
$sync_log_dur = (nsecs - @start_sync_log[tid]) / 1000;
printf("btrfs_log_inode() took %llu us\n", @log_inode_dur[tid]);
printf("btrfs_sync_log() took %llu us\n", $sync_log_dur);
delete(@start_sync_log[tid]);
delete(@log_inode_dur[tid]);
exit();
}
With 512M test file, before this patch:
btrfs_log_inode() took 15218 us
btrfs_sync_log() took 1328 us
Log tree has 17 leaves and 1 node, its total size is 294912 bytes.
With 512M test file, after this patch:
btrfs_log_inode() took 14760 us
btrfs_sync_log() took 588 us
Log tree has a single leaf, its total size is 16K.
With 1G test file, before this patch:
btrfs_log_inode() took 27301 us
btrfs_sync_log() took 1767 us
Log tree has 33 leaves and 1 node, its total size is 557056 bytes.
With 1G test file, after this patch:
btrfs_log_inode() took 26166 us
btrfs_sync_log() took 593 us
Log tree has a single leaf, its total size is 16K
With 2G test file, before this patch:
btrfs_log_inode() took 50892 us
btrfs_sync_log() took 3127 us
Log tree has 65 leaves and 1 node, its total size is 1081344 bytes.
With 2G test file, after this patch:
btrfs_log_inode() took 50126 us
btrfs_sync_log() took 586 us
Log tree has a single leaf, its total size is 16K.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
Now that all call sites are using the slot number to modify item values,
rename the SETGET helpers to raw_item_*(), and then rework the _nr()
helpers to be the btrfs_item_*() btrfs_set_item_*() helpers, and then
rename all of the callers to the new helpers.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
Although in btrfs we have very limited usage of PageChecked flag, it's
still some page flag not yet subpage compatible.
Fix it by introducing btrfs_subpage::checked_offset to do the convert.
For most call sites, especially for free-space cache, COW fixup and
btrfs_invalidatepage(), they all work in full page mode anyway.
For other call sites, they work as subpage compatible mode.
Some call sites need extra modification:
- btrfs_drop_pages()
Needs extra parameter to get the real range we need to clear checked
flag.
Also since btrfs_drop_pages() will accept pages beyond the dirtied
range, update btrfs_subpage_clamp_range() to handle such case
by setting @len to 0 if the page is beyond target range.
- btrfs_invalidatepage()
We need to call subpage helper before calling __btrfs_releasepage(),
or it will trigger ASSERT() as page->private will be cleared.
- btrfs_verify_data_csum()
In theory we don't need the io_bio->csum check anymore, but it's
won't hurt. Just change the comment.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
Fix a warning reported by smatch that ret could be returned without
initialized. The dedupe operations are supposed to to return 0 for a 0
length range but the caller does not pass olen == 0. To keep this
behaviour and also fix the warning initialize ret to 0.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Sidong Yang <realwakka@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
The modifications are:
- Page copy destination
For subpage case, one page can contain multiple sectors, thus we can
no longer expect the memcpy_to_page()/btrfs_decompress() to copy
data into page offset 0.
The correct offset is offset_in_page(file_offset) now, which should
handle both regular sectorsize and subpage cases well.
- Page status update
Now we need to use subpage helper to handle the page status update.
Tested-by: Ritesh Harjani <riteshh@linux.ibm.com> # [ppc64]
Tested-by: Anand Jain <anand.jain@oracle.com> # [aarch64]
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux
Pull btrfs fixes from David Sterba:
"Error handling improvements, caught by error injection:
- handle errors during checksum deletion
- set error on mapping when ordered extent io cannot be finished
- inode link count fixup in tree-log
- missing return value checks for inode updates in tree-log
- abort transaction in rename exchange if adding second reference
fails
Fixes:
- fix fsync failure after writes to prealloc extents
- fix deadlock when cloning inline extents and low on available space
- fix compressed writes that cross stripe boundary"
* tag 'for-5.13-rc4-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
MAINTAINERS: add btrfs IRC link
btrfs: fix deadlock when cloning inline extents and low on available space
btrfs: fix fsync failure and transaction abort after writes to prealloc extents
btrfs: abort in rename_exchange if we fail to insert the second ref
btrfs: check error value from btrfs_update_inode in tree log
btrfs: fixup error handling in fixup_inode_link_counts
btrfs: mark ordered extent and inode with error if we fail to finish
btrfs: return errors from btrfs_del_csums in cleanup_ref_head
btrfs: fix error handling in btrfs_del_csums
btrfs: fix compressed writes that cross stripe boundary
|
|
There are a few cases where cloning an inline extent requires copying data
into a page of the destination inode. For these cases we are allocating
the required data and metadata space while holding a leaf locked. This can
result in a deadlock when we are low on available space because allocating
the space may flush delalloc and two deadlock scenarios can happen:
1) When starting writeback for an inode with a very small dirty range that
fits in an inline extent, we deadlock during the writeback when trying
to insert the inline extent, at cow_file_range_inline(), if the extent
is going to be located in the leaf for which we are already holding a
read lock;
2) After successfully starting writeback, for non-inline extent cases,
the async reclaim thread will hang waiting for an ordered extent to
complete if the ordered extent completion needs to modify the leaf
for which the clone task is holding a read lock (for adding or
replacing file extent items). So the cloning task will wait forever
on the async reclaim thread to make progress, which in turn is
waiting for the ordered extent completion which in turn is waiting
to acquire a write lock on the same leaf.
So fix this by making sure we release the path (and therefore the leaf)
every time we need to copy the inline extent's data into a page of the
destination inode, as by that time we do not need to have the leaf locked.
Fixes: 05a5a7621ce66c ("Btrfs: implement full reflink support for inline extents")
CC: stable@vger.kernel.org # 5.10+
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux
Pull btrfs fixes from David Sterba:
"A few more fixes:
- fix unaligned compressed writes in zoned mode
- fix false positive lockdep warning when cloning inline extent
- remove wrong BUG_ON in tree-log error handling"
* tag 'for-5.13-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
btrfs: zoned: fix parallel compressed writes
btrfs: zoned: pass start block to btrfs_use_zone_append
btrfs: do not BUG_ON in link_to_fixup_dir
btrfs: release path before starting transaction when cloning inline extent
|
|
When cloning an inline extent there are a few cases, such as when we have
an implicit hole at file offset 0, where we start a transaction while
holding a read lock on a leaf. Starting the transaction results in a call
to sb_start_intwrite(), which results in doing a read lock on a percpu
semaphore. Lockdep doesn't like this and complains about it:
[46.580704] ======================================================
[46.580752] WARNING: possible circular locking dependency detected
[46.580799] 5.13.0-rc1 #28 Not tainted
[46.580832] ------------------------------------------------------
[46.580877] cloner/3835 is trying to acquire lock:
[46.580918] c00000001301d638 (sb_internal#2){.+.+}-{0:0}, at: clone_copy_inline_extent+0xe4/0x5a0
[46.581167]
[46.581167] but task is already holding lock:
[46.581217] c000000007fa2550 (btrfs-tree-00){++++}-{3:3}, at: __btrfs_tree_read_lock+0x70/0x1d0
[46.581293]
[46.581293] which lock already depends on the new lock.
[46.581293]
[46.581351]
[46.581351] the existing dependency chain (in reverse order) is:
[46.581410]
[46.581410] -> #1 (btrfs-tree-00){++++}-{3:3}:
[46.581464] down_read_nested+0x68/0x200
[46.581536] __btrfs_tree_read_lock+0x70/0x1d0
[46.581577] btrfs_read_lock_root_node+0x88/0x200
[46.581623] btrfs_search_slot+0x298/0xb70
[46.581665] btrfs_set_inode_index+0xfc/0x260
[46.581708] btrfs_new_inode+0x26c/0x950
[46.581749] btrfs_create+0xf4/0x2b0
[46.581782] lookup_open.isra.57+0x55c/0x6a0
[46.581855] path_openat+0x418/0xd20
[46.581888] do_filp_open+0x9c/0x130
[46.581920] do_sys_openat2+0x2ec/0x430
[46.581961] do_sys_open+0x90/0xc0
[46.581993] system_call_exception+0x3d4/0x410
[46.582037] system_call_common+0xec/0x278
[46.582078]
[46.582078] -> #0 (sb_internal#2){.+.+}-{0:0}:
[46.582135] __lock_acquire+0x1e90/0x2c50
[46.582176] lock_acquire+0x2b4/0x5b0
[46.582263] start_transaction+0x3cc/0x950
[46.582308] clone_copy_inline_extent+0xe4/0x5a0
[46.582353] btrfs_clone+0x5fc/0x880
[46.582388] btrfs_clone_files+0xd8/0x1c0
[46.582434] btrfs_remap_file_range+0x3d8/0x590
[46.582481] do_clone_file_range+0x10c/0x270
[46.582558] vfs_clone_file_range+0x1b0/0x310
[46.582605] ioctl_file_clone+0x90/0x130
[46.582651] do_vfs_ioctl+0x874/0x1ac0
[46.582697] sys_ioctl+0x6c/0x120
[46.582733] system_call_exception+0x3d4/0x410
[46.582777] system_call_common+0xec/0x278
[46.582822]
[46.582822] other info that might help us debug this:
[46.582822]
[46.582888] Possible unsafe locking scenario:
[46.582888]
[46.582942] CPU0 CPU1
[46.582984] ---- ----
[46.583028] lock(btrfs-tree-00);
[46.583062] lock(sb_internal#2);
[46.583119] lock(btrfs-tree-00);
[46.583174] lock(sb_internal#2);
[46.583212]
[46.583212] *** DEADLOCK ***
[46.583212]
[46.583266] 6 locks held by cloner/3835:
[46.583299] #0: c00000001301d448 (sb_writers#12){.+.+}-{0:0}, at: ioctl_file_clone+0x90/0x130
[46.583382] #1: c00000000f6d3768 (&sb->s_type->i_mutex_key#15){+.+.}-{3:3}, at: lock_two_nondirectories+0x58/0xc0
[46.583477] #2: c00000000f6d72a8 (&sb->s_type->i_mutex_key#15/4){+.+.}-{3:3}, at: lock_two_nondirectories+0x9c/0xc0
[46.583574] #3: c00000000f6d7138 (&ei->i_mmap_lock){+.+.}-{3:3}, at: btrfs_remap_file_range+0xd0/0x590
[46.583657] #4: c00000000f6d35f8 (&ei->i_mmap_lock/1){+.+.}-{3:3}, at: btrfs_remap_file_range+0xe0/0x590
[46.583743] #5: c000000007fa2550 (btrfs-tree-00){++++}-{3:3}, at: __btrfs_tree_read_lock+0x70/0x1d0
[46.583828]
[46.583828] stack backtrace:
[46.583872] CPU: 1 PID: 3835 Comm: cloner Not tainted 5.13.0-rc1 #28
[46.583931] Call Trace:
[46.583955] [c0000000167c7200] [c000000000c1ee78] dump_stack+0xec/0x144 (unreliable)
[46.584052] [c0000000167c7240] [c000000000274058] print_circular_bug.isra.32+0x3a8/0x400
[46.584123] [c0000000167c72e0] [c0000000002741f4] check_noncircular+0x144/0x190
[46.584191] [c0000000167c73b0] [c000000000278fc0] __lock_acquire+0x1e90/0x2c50
[46.584259] [c0000000167c74f0] [c00000000027aa94] lock_acquire+0x2b4/0x5b0
[46.584317] [c0000000167c75e0] [c000000000a0d6cc] start_transaction+0x3cc/0x950
[46.584388] [c0000000167c7690] [c000000000af47a4] clone_copy_inline_extent+0xe4/0x5a0
[46.584457] [c0000000167c77c0] [c000000000af525c] btrfs_clone+0x5fc/0x880
[46.584514] [c0000000167c7990] [c000000000af5698] btrfs_clone_files+0xd8/0x1c0
[46.584583] [c0000000167c7a00] [c000000000af5b58] btrfs_remap_file_range+0x3d8/0x590
[46.584652] [c0000000167c7ae0] [c0000000005d81dc] do_clone_file_range+0x10c/0x270
[46.584722] [c0000000167c7b40] [c0000000005d84f0] vfs_clone_file_range+0x1b0/0x310
[46.584793] [c0000000167c7bb0] [c00000000058bf80] ioctl_file_clone+0x90/0x130
[46.584861] [c0000000167c7c10] [c00000000058c894] do_vfs_ioctl+0x874/0x1ac0
[46.584922] [c0000000167c7d10] [c00000000058db4c] sys_ioctl+0x6c/0x120
[46.584978] [c0000000167c7d60] [c0000000000364a4] system_call_exception+0x3d4/0x410
[46.585046] [c0000000167c7e10] [c00000000000d45c] system_call_common+0xec/0x278
[46.585114] --- interrupt: c00 at 0x7ffff7e22990
[46.585160] NIP: 00007ffff7e22990 LR: 00000001000010ec CTR: 0000000000000000
[46.585224] REGS: c0000000167c7e80 TRAP: 0c00 Not tainted (5.13.0-rc1)
[46.585280] MSR: 800000000280f033 <SF,VEC,VSX,EE,PR,FP,ME,IR,DR,RI,LE> CR: 28000244 XER: 00000000
[46.585374] IRQMASK: 0
[46.585374] GPR00: 0000000000000036 00007fffffffdec0 00007ffff7f17100 0000000000000004
[46.585374] GPR04: 000000008020940d 00007fffffffdf40 0000000000000000 0000000000000000
[46.585374] GPR08: 0000000000000004 0000000000000000 0000000000000000 0000000000000000
[46.585374] GPR12: 0000000000000000 00007ffff7ffa940 0000000000000000 0000000000000000
[46.585374] GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[46.585374] GPR20: 0000000000000000 000000009123683e 00007fffffffdf40 0000000000000000
[46.585374] GPR24: 0000000000000000 0000000000000000 0000000000000000 0000000000000004
[46.585374] GPR28: 0000000100030260 0000000100030280 0000000000000003 000000000000005f
[46.585919] NIP [00007ffff7e22990] 0x7ffff7e22990
[46.585964] LR [00000001000010ec] 0x1000010ec
[46.586010] --- interrupt: c00
This should be a false positive, as both locks are acquired in read mode.
Nevertheless, we don't need to hold a leaf locked when we start the
transaction, so just release the leaf (path) before starting it.
Reported-by: Ritesh Harjani <riteshh@linux.ibm.com>
Link: https://lore.kernel.org/linux-btrfs/20210513214404.xks77p566fglzgum@riteshh-domain/
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
There are many places where kmap/memset/kunmap patterns occur.
Use the newly lifted memzero_page() to eliminate direct uses of kmap and
leverage the new core functions use of kmap_local_page().
The development of this patch was aided by the following coccinelle
script:
// <smpl>
// SPDX-License-Identifier: GPL-2.0-only
// Find kmap/memset/kunmap pattern and replace with memset*page calls
//
// NOTE: Offsets and other expressions may be more complex than what the script
// will automatically generate. Therefore a catchall rule is provided to find
// the pattern which then must be evaluated by hand.
//
// Confidence: Low
// Copyright: (C) 2021 Intel Corporation
// URL: http://coccinelle.lip6.fr/
// Comments:
// Options:
//
// Then the memset pattern
//
@ memset_rule1 @
expression page, V, L, Off;
identifier ptr;
type VP;
@@
(
-VP ptr = kmap(page);
|
-ptr = kmap(page);
|
-VP ptr = kmap_atomic(page);
|
-ptr = kmap_atomic(page);
)
<+...
(
-memset(ptr, 0, L);
+memzero_page(page, 0, L);
|
-memset(ptr + Off, 0, L);
+memzero_page(page, Off, L);
|
-memset(ptr, V, L);
+memset_page(page, V, 0, L);
|
-memset(ptr + Off, V, L);
+memset_page(page, V, Off, L);
)
...+>
(
-kunmap(page);
|
-kunmap_atomic(ptr);
)
// Remove any pointers left unused
@
depends on memset_rule1
@
identifier memset_rule1.ptr;
type VP, VP1;
@@
-VP ptr;
... when != ptr;
? VP1 ptr;
//
// Catch all
//
@ memset_rule2 @
expression page;
identifier ptr;
expression GenTo, GenSize, GenValue;
type VP;
@@
(
-VP ptr = kmap(page);
|
-ptr = kmap(page);
|
-VP ptr = kmap_atomic(page);
|
-ptr = kmap_atomic(page);
)
<+...
(
//
// Some call sites have complex expressions within the memset/memcpy
// The follow are catch alls which need to be evaluated by hand.
//
-memset(GenTo, 0, GenSize);
+memzero_pageExtra(page, GenTo, GenSize);
|
-memset(GenTo, GenValue, GenSize);
+memset_pageExtra(page, GenValue, GenTo, GenSize);
)
...+>
(
-kunmap(page);
|
-kunmap_atomic(ptr);
)
// Remove any pointers left unused
@
depends on memset_rule2
@
identifier memset_rule2.ptr;
type VP, VP1;
@@
-VP ptr;
... when != ptr;
? VP1 ptr;
// </smpl>
Link: https://lkml.kernel.org/r/20210309212137.2610186-4-ira.weiny@intel.com
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
If we reflink to or from a file opened with O_SYNC/O_DSYNC or to/from a
file that has the S_SYNC attribute set, we totally ignore that and do not
durably persist the reflink changes. Since a reflink can change the data
readable from a file (and mtime/ctime, or a file size), it makes sense to
durably persist (fsync) the source and destination files/ranges.
This was previously discussed at:
https://lore.kernel.org/linux-btrfs/20200903035225.GJ6090@magnolia/
The recently introduced test case generic/628, from fstests, exercises
these scenarios and currently fails without this change.
So make sure we fsync the source and destination files/ranges when either
of them was opened with O_SYNC/O_DSYNC or has the S_SYNC attribute set,
just like XFS already does.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
Darrick reported a potential issue to me where we could allow mmap
writes after validating a page range matched in the case of dedupe.
Generally we rely on lock page -> lock extent with the ordered flush to
protect us, but this is done after we check the pages because we use the
generic helpers, so we could modify the page in between doing the check
and locking the range.
There also exists a deadlock, as described by Filipe
"""
When cloning a file range, we lock the inodes, flush any delalloc within
the respective file ranges, wait for any ordered extents and then lock the
file ranges in both inodes. This means that right after we flush delalloc
and before we lock the file ranges, memory mapped writes can come in and
dirty pages in the file ranges of the clone operation.
Most of the time this is harmless and causes no problems. However, if we
are low on available metadata space, we can later end up in a deadlock
when starting a transaction to replace file extent items. This happens if
when allocating metadata space for the transaction, we need to wait for
the async reclaim thread to release space and the reclaim thread needs to
flush delalloc for the inode that got the memory mapped write and has its
range locked by the clone task.
Basically what happens is the following:
1) A clone operation locks inodes A and B, flushes delalloc for both
inodes in the respective file ranges and waits for any ordered extents
in those ranges to complete;
2) Before the clone task locks the file ranges, another task does a
memory mapped write (which does not lock the inode) for one of the
inodes of the clone operation. So now we have a dirty page in one of
the ranges used by the clone operation;
3) The clone operation locks the file ranges for inodes A and B;
4) Later, when iterating over the file extents of inode A, the clone
task attempts to start a transaction. There's not enough available
free metadata space, so the async reclaim task is started (if not
running already) and we wait for someone to wake us up on our
reservation ticket;
5) The async reclaim task is not able to release space by any other
means and decides to flush delalloc for the inode of the clone
operation;
6) The workqueue job used to flush the inode blocks when starting
delalloc for the inode, since the file range is currently locked by
the clone task;
7) But the clone task is waiting on its reservation ticket and the async
reclaim task is waiting on the flush job to complete, which can't
progress since the clone task has the file range locked. So unless
some other task is able to release space, for example an ordered
extent for some other inode completes, we have a deadlock between all
these tasks;
When this happens stack traces like the following show up in dmesg/syslog:
INFO: task kworker/u16:11:1810830 blocked for more than 120 seconds.
Tainted: G B W 5.10.0-rc4-btrfs-next-73 #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u16:11 state:D stack: 0 pid:1810830 ppid: 2 flags:0x00004000
Workqueue: btrfs-flush_delalloc btrfs_work_helper [btrfs]
Call Trace:
__schedule+0x5d1/0xcf0
schedule+0x45/0xe0
lock_extent_bits+0x1e6/0x2d0 [btrfs]
? finish_wait+0x90/0x90
btrfs_invalidatepage+0x32c/0x390 [btrfs]
? __mod_memcg_state+0x8e/0x160
__extent_writepage+0x2d4/0x400 [btrfs]
extent_write_cache_pages+0x2b2/0x500 [btrfs]
? lock_release+0x20e/0x4c0
? trace_hardirqs_on+0x1b/0xf0
extent_writepages+0x43/0x90 [btrfs]
? lock_acquire+0x1a3/0x490
do_writepages+0x43/0xe0
? __filemap_fdatawrite_range+0xa4/0x100
__filemap_fdatawrite_range+0xc5/0x100
btrfs_run_delalloc_work+0x17/0x40 [btrfs]
btrfs_work_helper+0xf1/0x600 [btrfs]
process_one_work+0x24e/0x5e0
worker_thread+0x50/0x3b0
? process_one_work+0x5e0/0x5e0
kthread+0x153/0x170
? kthread_mod_delayed_work+0xc0/0xc0
ret_from_fork+0x22/0x30
INFO: task kworker/u16:1:2426217 blocked for more than 120 seconds.
Tainted: G B W 5.10.0-rc4-btrfs-next-73 #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u16:1 state:D stack: 0 pid:2426217 ppid: 2 flags:0x00004000
Workqueue: events_unbound btrfs_async_reclaim_metadata_space [btrfs]
Call Trace:
__schedule+0x5d1/0xcf0
? kvm_clock_read+0x14/0x30
? wait_for_completion+0x81/0x110
schedule+0x45/0xe0
schedule_timeout+0x30c/0x580
? _raw_spin_unlock_irqrestore+0x3c/0x60
? lock_acquire+0x1a3/0x490
? try_to_wake_up+0x7a/0xa20
? lock_release+0x20e/0x4c0
? lock_acquired+0x199/0x490
? wait_for_completion+0x81/0x110
wait_for_completion+0xab/0x110
start_delalloc_inodes+0x2af/0x390 [btrfs]
btrfs_start_delalloc_roots+0x12d/0x250 [btrfs]
flush_space+0x24f/0x660 [btrfs]
btrfs_async_reclaim_metadata_space+0x1bb/0x480 [btrfs]
process_one_work+0x24e/0x5e0
worker_thread+0x20f/0x3b0
? process_one_work+0x5e0/0x5e0
kthread+0x153/0x170
? kthread_mod_delayed_work+0xc0/0xc0
ret_from_fork+0x22/0x30
(...)
several other tasks blocked on inode locks held by the clone task below
(...)
RIP: 0033:0x7f61efe73fff
Code: Unable to access opcode bytes at RIP 0x7f61efe73fd5.
RSP: 002b:00007ffc3371bbe8 EFLAGS: 00000202 ORIG_RAX: 000000000000013c
RAX: ffffffffffffffda RBX: 00007ffc3371bea0 RCX: 00007f61efe73fff
RDX: 00000000ffffff9c RSI: 0000560fbd604690 RDI: 00000000ffffff9c
RBP: 00007ffc3371beb0 R08: 0000000000000002 R09: 0000560fbd5d75f0
R10: 0000560fbd5d81f0 R11: 0000000000000202 R12: 0000000000000002
R13: 000000000000000b R14: 00007ffc3371bea0 R15: 00007ffc3371beb0
task: fdm-stress state:D stack: 0 pid:2508234 ppid:2508153 flags:0x00004000
Call Trace:
__schedule+0x5d1/0xcf0
? _raw_spin_unlock_irqrestore+0x3c/0x60
schedule+0x45/0xe0
__reserve_bytes+0x4a4/0xb10 [btrfs]
? finish_wait+0x90/0x90
btrfs_reserve_metadata_bytes+0x29/0x190 [btrfs]
btrfs_block_rsv_add+0x1f/0x50 [btrfs]
start_transaction+0x2d1/0x760 [btrfs]
btrfs_replace_file_extents+0x120/0x930 [btrfs]
? lock_release+0x20e/0x4c0
btrfs_clone+0x3e4/0x7e0 [btrfs]
? btrfs_lookup_first_ordered_extent+0x8e/0x100 [btrfs]
btrfs_clone_files+0xf6/0x150 [btrfs]
btrfs_remap_file_range+0x324/0x3d0 [btrfs]
do_clone_file_range+0xd4/0x1f0
vfs_clone_file_range+0x4d/0x230
? lock_release+0x20e/0x4c0
ioctl_file_clone+0x8f/0xc0
do_vfs_ioctl+0x342/0x750
__x64_sys_ioctl+0x62/0xb0
do_syscall_64+0x33/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xa9
"""
Fix both of these issues by excluding mmaps from happening we are doing
any sort of remap, which prevents this race completely.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
A few places we intermix btrfs_inode_lock with a inode_unlock, and some
places we just use inode_lock/inode_unlock instead of btrfs_inode_lock.
None of these places are using this incorrectly, but as we adjust some
of these callers it would be nice to keep everything consistent, so
convert everybody to use btrfs_inode_lock/btrfs_inode_unlock.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux
Pull kmap conversion updates from David Sterba:
"This contains changes regarding kmap API use and eg conversion from
kmap_atomic to kmap_local_page.
The API belongs to memory management but to save cross-tree
dependency headaches we've agreed to take it through the btrfs tree
because there are some trivial conversions possible, while the rest
will need some time and getting the easy cases out of the way would be
convenient.
The changes can be grouped:
- function exports, new helpers
- new VM_BUG_ON for additional verification; it's been discussed if
it should be VM_BUG_ON or BUG_ON, the former was chosen due to
performance reasons
- code replaced by relevant helpers"
[ This is an updated version of a request that originally came in during
the merge window, but I asked for some updates:
https://lore.kernel.org/lkml/cover.1614090658.git.dsterba@suse.com/
which is why this got merge after the merge window closed. - Linus ]
* 'kmap-conversion-for-5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
btrfs: use copy_highpage() instead of 2 kmaps()
btrfs: use memcpy_[to|from]_page() and kmap_local_page()
mm/highmem: Add VM_BUG_ON() to mem*_page() calls
mm/highmem: Introduce memcpy_page(), memmove_page(), and memset_page()
mm/highmem: Convert memcpy_[to|from]_page() to kmap_local_page()
mm/highmem: Lift memcpy_[to|from]_page to core
|
|
There are many places where the pattern kmap/memcpy/kunmap occurs.
This pattern was lifted to the core common functions
memcpy_[to|from]_page().
Use these new functions to reduce the code, eliminate direct uses of
kmap, and leverage the new core functions use of kmap_local_page().
Also, there is 1 place where a kmap/memcpy is followed by an
optional memset. Here we leave the kmap open coded to avoid remapping
the page but use kmap_local_page() directly.
Development of this patch was aided by the coccinelle script:
// <smpl>
// SPDX-License-Identifier: GPL-2.0-only
// Find kmap/memcpy/kunmap pattern and replace with memcpy*page calls
//
// NOTE: Offsets and other expressions may be more complex than what the script
// will automatically generate. Therefore a catchall rule is provided to find
// the pattern which then must be evaluated by hand.
//
// Confidence: Low
// Copyright: (C) 2021 Intel Corporation
// URL: http://coccinelle.lip6.fr/
// Comments:
// Options:
//
// simple memcpy version
//
@ memcpy_rule1 @
expression page, T, F, B, Off;
identifier ptr;
type VP;
@@
(
-VP ptr = kmap(page);
|
-ptr = kmap(page);
|
-VP ptr = kmap_atomic(page);
|
-ptr = kmap_atomic(page);
)
<+...
(
-memcpy(ptr + Off, F, B);
+memcpy_to_page(page, Off, F, B);
|
-memcpy(ptr, F, B);
+memcpy_to_page(page, 0, F, B);
|
-memcpy(T, ptr + Off, B);
+memcpy_from_page(T, page, Off, B);
|
-memcpy(T, ptr, B);
+memcpy_from_page(T, page, 0, B);
)
...+>
(
-kunmap(page);
|
-kunmap_atomic(ptr);
)
// Remove any pointers left unused
@
depends on memcpy_rule1
@
identifier memcpy_rule1.ptr;
type VP, VP1;
@@
-VP ptr;
... when != ptr;
? VP1 ptr;
//
// Some callers kmap without a temp pointer
//
@ memcpy_rule2 @
expression page, T, Off, F, B;
@@
<+...
(
-memcpy(kmap(page) + Off, F, B);
+memcpy_to_page(page, Off, F, B);
|
-memcpy(kmap(page), F, B);
+memcpy_to_page(page, 0, F, B);
|
-memcpy(T, kmap(page) + Off, B);
+memcpy_from_page(T, page, Off, B);
|
-memcpy(T, kmap(page), B);
+memcpy_from_page(T, page, 0, B);
)
...+>
-kunmap(page);
// No need for the ptr variable removal
//
// Catch all
//
@ memcpy_rule3 @
expression page;
expression GenTo, GenFrom, GenSize;
identifier ptr;
type VP;
@@
(
-VP ptr = kmap(page);
|
-ptr = kmap(page);
|
-VP ptr = kmap_atomic(page);
|
-ptr = kmap_atomic(page);
)
<+...
(
//
// Some call sites have complex expressions within the memcpy
// match a catch all to be evaluated by hand.
//
-memcpy(GenTo, GenFrom, GenSize);
+memcpy_to_pageExtra(page, GenTo, GenFrom, GenSize);
+memcpy_from_pageExtra(GenTo, page, GenFrom, GenSize);
)
...+>
(
-kunmap(page);
|
-kunmap_atomic(ptr);
)
// Remove any pointers left unused
@
depends on memcpy_rule3
@
identifier memcpy_rule3.ptr;
type VP, VP1;
@@
-VP ptr;
... when != ptr;
? VP1 ptr;
// <smpl>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
When using the NO_HOLES feature, if we clone a file range that spans only
a hole into a range that is at or beyond the current i_size of the
destination file, we end up not setting the full sync runtime flag on the
inode. As a result, if we then fsync the destination file and have a power
failure, after log replay we can end up exposing stale data instead of
having a hole for that range.
The conditions for this to happen are the following:
1) We have a file with a size of, for example, 1280K;
2) There is a written (non-prealloc) extent for the file range from 1024K
to 1280K with a length of 256K;
3) This particular file extent layout is durably persisted, so that the
existing superblock persisted on disk points to a subvolume root where
the file has that exact file extent layout and state;
4) The file is truncated to a smaller size, to an offset lower than the
start offset of its last extent, for example to 800K. The truncate sets
the full sync runtime flag on the inode;
6) Fsync the file to log it and clear the full sync runtime flag;
7) Clone a region that covers only a hole (implicit hole due to NO_HOLES)
into the file with a destination offset that starts at or beyond the
256K file extent item we had - for example to offset 1024K;
8) Since the clone operation does not find extents in the source range,
we end up in the if branch at the bottom of btrfs_clone() where we
punch a hole for the file range starting at offset 1024K by calling
btrfs_replace_file_extents(). There we end up not setting the full
sync flag on the inode, because we don't know we are being called in
a clone context (and not fallocate's punch hole operation), and
neither do we create an extent map to represent a hole because the
requested range is beyond eof;
9) A further fsync to the file will be a fast fsync, since the clone
operation did not set the full sync flag, and therefore it relies on
modified extent maps to correctly log the file layout. But since
it does not find any extent map marking the range from 1024K (the
previous eof) to the new eof, it does not log a file extent item
for that range representing the hole;
10) After a power failure no hole for the range starting at 1024K is
punched and we end up exposing stale data from the old 256K extent.
Turning this into exact steps:
$ mkfs.btrfs -f -O no-holes /dev/sdi
$ mount /dev/sdi /mnt
# Create our test file with 3 extents of 256K and a 256K hole at offset
# 256K. The file has a size of 1280K.
$ xfs_io -f -s \
-c "pwrite -S 0xab -b 256K 0 256K" \
-c "pwrite -S 0xcd -b 256K 512K 256K" \
-c "pwrite -S 0xef -b 256K 768K 256K" \
-c "pwrite -S 0x73 -b 256K 1024K 256K" \
/mnt/sdi/foobar
# Make sure it's durably persisted. We want the last committed super
# block to point to this particular file extent layout.
sync
# Now truncate our file to a smaller size, falling within a position of
# the second extent. This sets the full sync runtime flag on the inode.
# Then fsync the file to log it and clear the full sync flag from the
# inode. The third extent is no longer part of the file and therefore
# it is not logged.
$ xfs_io -c "truncate 800K" -c "fsync" /mnt/foobar
# Now do a clone operation that only clones the hole and sets back the
# file size to match the size it had before the truncate operation
# (1280K).
$ xfs_io \
-c "reflink /mnt/foobar 256K 1024K 256K" \
-c "fsync" \
/mnt/foobar
# File data before power failure:
$ od -A d -t x1 /mnt/foobar
0000000 ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab
*
0262144 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
*
0524288 cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd
*
0786432 ef ef ef ef ef ef ef ef ef ef ef ef ef ef ef ef
*
0819200 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
*
1310720
<power fail>
# Mount the fs again to replay the log tree.
$ mount /dev/sdi /mnt
# File data after power failure:
$ od -A d -t x1 /mnt/foobar
0000000 ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab
*
0262144 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
*
0524288 cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd
*
0786432 ef ef ef ef ef ef ef ef ef ef ef ef ef ef ef ef
*
0819200 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
*
1048576 73 73 73 73 73 73 73 73 73 73 73 73 73 73 73 73
*
1310720
The range from 1024K to 1280K should correspond to a hole but instead it
points to stale data, to the 256K extent that should not exist after the
truncate operation.
The issue does not exists when not using NO_HOLES, because for that case
we use file extent items to represent holes, these are found and copied
during the loop that iterates over extents at btrfs_clone(), and that
causes btrfs_replace_file_extents() to be called with a non-NULL
extent_info argument and therefore set the full sync runtime flag on the
inode.
So fix this by making the code that deals with a trailing hole during
cloning, at btrfs_clone(), to set the full sync flag on the inode, if the
range starts at or beyond the current i_size.
A test case for fstests will follow soon.
Backporting notes: for kernel 5.4 the change goes to ioctl.c into
btrfs_clone before the last call to btrfs_punch_hole_range.
CC: stable@vger.kernel.org # 5.4+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
To support subpage sector size, data also need extra info to make sure
which sectors in a page are uptodate/dirty/...
This patch will make pages for data inodes get btrfs_subpage structure
attached, and detached when the page is freed.
This patch also slightly changes the timing when
set_page_extent_mapped() is called to make sure:
- We have page->mapping set
page->mapping->host is used to grab btrfs_fs_info, thus we can only
call this function after page is mapped to an inode.
One call site attaches pages to inode manually, thus we have to modify
the timing of set_page_extent_mapped() a bit.
- As soon as possible, before other operations
Since memory allocation can fail, we have to do extra error handling.
Calling set_page_extent_mapped() as soon as possible can simply the
error handling for several call sites.
The idea is pretty much the same as iomap_page, but with more bitmaps
for btrfs specific cases.
Currently the plan is to switch iomap if iomap can provide sector
aligned write back (only write back dirty sectors, but not the full
page, data balance require this feature).
So we will stick to btrfs specific bitmap for now.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
When cloning an inline extent there are cases where we can not just copy
the inline extent from the source range to the target range (e.g. when the
target range starts at an offset greater than zero). In such cases we copy
the inline extent's data into a page of the destination inode and then
dirty that page. However, after that we will need to start a transaction
for each processed extent and, if we are ever low on available metadata
space, we may need to flush existing delalloc for all dirty inodes in an
attempt to release metadata space - if that happens we may deadlock:
* the async reclaim task queued a delalloc work to flush delalloc for
the destination inode of the clone operation;
* the task executing that delalloc work gets blocked waiting for the
range with the dirty page to be unlocked, which is currently locked
by the task doing the clone operation;
* the async reclaim task blocks waiting for the delalloc work to complete;
* the cloning task is waiting on the waitqueue of its reservation ticket
while holding the range with the dirty page locked in the inode's
io_tree;
* if metadata space is not released by some other task (like delalloc for
some other inode completing for example), the clone task waits forever
and as a consequence the delalloc work and async reclaim tasks will hang
forever as well. Releasing more space on the other hand may require
starting a transaction, which will hang as well when trying to reserve
metadata space, resulting in a deadlock between all these tasks.
When this happens, traces like the following show up in dmesg/syslog:
[87452.323003] INFO: task kworker/u16:11:1810830 blocked for more than 120 seconds.
[87452.323644] Tainted: G B W 5.10.0-rc4-btrfs-next-73 #1
[87452.324248] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[87452.324852] task:kworker/u16:11 state:D stack: 0 pid:1810830 ppid: 2 flags:0x00004000
[87452.325520] Workqueue: btrfs-flush_delalloc btrfs_work_helper [btrfs]
[87452.326136] Call Trace:
[87452.326737] __schedule+0x5d1/0xcf0
[87452.327390] schedule+0x45/0xe0
[87452.328174] lock_extent_bits+0x1e6/0x2d0 [btrfs]
[87452.328894] ? finish_wait+0x90/0x90
[87452.329474] btrfs_invalidatepage+0x32c/0x390 [btrfs]
[87452.330133] ? __mod_memcg_state+0x8e/0x160
[87452.330738] __extent_writepage+0x2d4/0x400 [btrfs]
[87452.331405] extent_write_cache_pages+0x2b2/0x500 [btrfs]
[87452.332007] ? lock_release+0x20e/0x4c0
[87452.332557] ? trace_hardirqs_on+0x1b/0xf0
[87452.333127] extent_writepages+0x43/0x90 [btrfs]
[87452.333653] ? lock_acquire+0x1a3/0x490
[87452.334177] do_writepages+0x43/0xe0
[87452.334699] ? __filemap_fdatawrite_range+0xa4/0x100
[87452.335720] __filemap_fdatawrite_range+0xc5/0x100
[87452.336500] btrfs_run_delalloc_work+0x17/0x40 [btrfs]
[87452.337216] btrfs_work_helper+0xf1/0x600 [btrfs]
[87452.337838] process_one_work+0x24e/0x5e0
[87452.338437] worker_thread+0x50/0x3b0
[87452.339137] ? process_one_work+0x5e0/0x5e0
[87452.339884] kthread+0x153/0x170
[87452.340507] ? kthread_mod_delayed_work+0xc0/0xc0
[87452.341153] ret_from_fork+0x22/0x30
[87452.341806] INFO: task kworker/u16:1:2426217 blocked for more than 120 seconds.
[87452.342487] Tainted: G B W 5.10.0-rc4-btrfs-next-73 #1
[87452.343274] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[87452.344049] task:kworker/u16:1 state:D stack: 0 pid:2426217 ppid: 2 flags:0x00004000
[87452.344974] Workqueue: events_unbound btrfs_async_reclaim_metadata_space [btrfs]
[87452.345655] Call Trace:
[87452.346305] __schedule+0x5d1/0xcf0
[87452.346947] ? kvm_clock_read+0x14/0x30
[87452.347676] ? wait_for_completion+0x81/0x110
[87452.348389] schedule+0x45/0xe0
[87452.349077] schedule_timeout+0x30c/0x580
[87452.349718] ? _raw_spin_unlock_irqrestore+0x3c/0x60
[87452.350340] ? lock_acquire+0x1a3/0x490
[87452.351006] ? try_to_wake_up+0x7a/0xa20
[87452.351541] ? lock_release+0x20e/0x4c0
[87452.352040] ? lock_acquired+0x199/0x490
[87452.352517] ? wait_for_completion+0x81/0x110
[87452.353000] wait_for_completion+0xab/0x110
[87452.353490] start_delalloc_inodes+0x2af/0x390 [btrfs]
[87452.353973] btrfs_start_delalloc_roots+0x12d/0x250 [btrfs]
[87452.354455] flush_space+0x24f/0x660 [btrfs]
[87452.355063] btrfs_async_reclaim_metadata_space+0x1bb/0x480 [btrfs]
[87452.355565] process_one_work+0x24e/0x5e0
[87452.356024] worker_thread+0x20f/0x3b0
[87452.356487] ? process_one_work+0x5e0/0x5e0
[87452.356973] kthread+0x153/0x170
[87452.357434] ? kthread_mod_delayed_work+0xc0/0xc0
[87452.357880] ret_from_fork+0x22/0x30
(...)
< stack traces of several tasks waiting for the locks of the inodes of the
clone operation >
(...)
[92867.444138] RSP: 002b:00007ffc3371bbe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000052
[92867.444624] RAX: ffffffffffffffda RBX: 00007ffc3371bea0 RCX: 00007f61efe73f97
[92867.445116] RDX: 0000000000000000 RSI: 0000560fbd5d7a40 RDI: 0000560fbd5d8960
[92867.445595] RBP: 00007ffc3371beb0 R08: 0000000000000001 R09: 0000000000000003
[92867.446070] R10: 00007ffc3371b996 R11: 0000000000000246 R12: 0000000000000000
[92867.446820] R13: 000000000000001f R14: 00007ffc3371bea0 R15: 00007ffc3371beb0
[92867.447361] task:fsstress state:D stack: 0 pid:2508238 ppid:2508153 flags:0x00004000
[92867.447920] Call Trace:
[92867.448435] __schedule+0x5d1/0xcf0
[92867.448934] ? _raw_spin_unlock_irqrestore+0x3c/0x60
[92867.449423] schedule+0x45/0xe0
[92867.449916] __reserve_bytes+0x4a4/0xb10 [btrfs]
[92867.450576] ? finish_wait+0x90/0x90
[92867.451202] btrfs_reserve_metadata_bytes+0x29/0x190 [btrfs]
[92867.451815] btrfs_block_rsv_add+0x1f/0x50 [btrfs]
[92867.452412] start_transaction+0x2d1/0x760 [btrfs]
[92867.453216] clone_copy_inline_extent+0x333/0x490 [btrfs]
[92867.453848] ? lock_release+0x20e/0x4c0
[92867.454539] ? btrfs_search_slot+0x9a7/0xc30 [btrfs]
[92867.455218] btrfs_clone+0x569/0x7e0 [btrfs]
[92867.455952] btrfs_clone_files+0xf6/0x150 [btrfs]
[92867.456588] btrfs_remap_file_range+0x324/0x3d0 [btrfs]
[92867.457213] do_clone_file_range+0xd4/0x1f0
[92867.457828] vfs_clone_file_range+0x4d/0x230
[92867.458355] ? lock_release+0x20e/0x4c0
[92867.458890] ioctl_file_clone+0x8f/0xc0
[92867.459377] do_vfs_ioctl+0x342/0x750
[92867.459913] __x64_sys_ioctl+0x62/0xb0
[92867.460377] do_syscall_64+0x33/0x80
[92867.460842] entry_SYSCALL_64_after_hwframe+0x44/0xa9
(...)
< stack traces of more tasks blocked on metadata reservation like the clone
task above, because the async reclaim task has deadlocked >
(...)
Another thing to notice is that the worker task that is deadlocked when
trying to flush the destination inode of the clone operation is at
btrfs_invalidatepage(). This is simply because the clone operation has a
destination offset greater than the i_size and we only update the i_size
of the destination file after cloning an extent (just like we do in the
buffered write path).
Since the async reclaim path uses btrfs_start_delalloc_roots() to trigger
the flushing of delalloc for all inodes that have delalloc, add a runtime
flag to an inode to signal it should not be flushed, and for inodes with
that flag set, start_delalloc_inodes() will simply skip them. When the
cloning code needs to dirty a page to copy an inline extent, set that flag
on the inode and then clear it when the clone operation finishes.
This could be sporadically triggered with test case generic/269 from
fstests, which exercises many fsstress processes running in parallel with
several dd processes filling up the entire filesystem.
CC: stable@vger.kernel.org # 5.9+
Fixes: 05a5a7621ce6 ("Btrfs: implement full reflink support for inline extents")
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
There are several occasions where we do not update the inode's number of
used bytes atomically, resulting in a concurrent stat(2) syscall to report
a value of used blocks that does not correspond to a valid value, that is,
a value that does not match neither what we had before the operation nor
what we get after the operation completes.
In extreme cases it can result in stat(2) reporting zero used blocks, which
can cause problems for some userspace tools where they can consider a file
with a non-zero size and zero used blocks as completely sparse and skip
reading data, as reported/discussed a long time ago in some threads like
the following:
https://lists.gnu.org/archive/html/bug-tar/2016-07/msg00001.html
The cases where this can happen are the following:
-> Case 1
If we do a write (buffered or direct IO) against a file region for which
there is already an allocated extent (or multiple extents), then we have a
short time window where we can report a number of used blocks to stat(2)
that does not take into account the file region being overwritten. This
short time window happens when completing the ordered extent(s).
This happens because when we drop the extents in the write range we
decrement the inode's number of bytes and later on when we insert the new
extent(s) we increment the number of bytes in the inode, resulting in a
short time window where a stat(2) syscall can get an incorrect number of
used blocks.
If we do writes that overwrite an entire file, then we have a short time
window where we report 0 used blocks to stat(2).
Example reproducer:
$ cat reproducer-1.sh
#!/bin/bash
MNT=/mnt/sdi
DEV=/dev/sdi
stat_loop()
{
trap "wait; exit" SIGTERM
local filepath=$1
local expected=$2
local got
while :; do
got=$(stat -c %b $filepath)
if [ $got -ne $expected ]; then
echo -n "ERROR: unexpected used blocks"
echo " (got: $got expected: $expected)"
fi
done
}
mkfs.btrfs -f $DEV > /dev/null
# mkfs.xfs -f $DEV > /dev/null
# mkfs.ext4 -F $DEV > /dev/null
# mkfs.f2fs -f $DEV > /dev/null
# mkfs.reiserfs -f $DEV > /dev/null
mount $DEV $MNT
xfs_io -f -s -c "pwrite -b 64K 0 64K" $MNT/foobar >/dev/null
expected=$(stat -c %b $MNT/foobar)
# Create a process to keep calling stat(2) on the file and see if the
# reported number of blocks used (disk space used) changes, it should
# not because we are not increasing the file size nor punching holes.
stat_loop $MNT/foobar $expected &
loop_pid=$!
for ((i = 0; i < 50000; i++)); do
xfs_io -s -c "pwrite -b 64K 0 64K" $MNT/foobar >/dev/null
done
kill $loop_pid &> /dev/null
wait
umount $DEV
$ ./reproducer-1.sh
ERROR: unexpected used blocks (got: 0 expected: 128)
ERROR: unexpected used blocks (got: 0 expected: 128)
(...)
Note that since this is a short time window where the race can happen, the
reproducer may not be able to always trigger the bug in one run, or it may
trigger it multiple times.
-> Case 2
If we do a buffered write against a file region that does not have any
allocated extents, like a hole or beyond EOF, then during ordered extent
completion we have a short time window where a concurrent stat(2) syscall
can report a number of used blocks that does not correspond to the value
before or after the write operation, a value that is actually larger than
the value after the write completes.
This happens because once we start a buffered write into an unallocated
file range we increment the inode's 'new_delalloc_bytes', to make sure
any stat(2) call gets a correct used blocks value before delalloc is
flushed and completes. However at ordered extent completion, after we
inserted the new extent, we increment the inode's number of bytes used
with the size of the new extent, and only later, when clearing the range
in the inode's iotree, we decrement the inode's 'new_delalloc_bytes'
counter with the size of the extent. So this results in a short time
window where a concurrent stat(2) syscall can report a number of used
blocks that accounts for the new extent twice.
Example reproducer:
$ cat reproducer-2.sh
#!/bin/bash
MNT=/mnt/sdi
DEV=/dev/sdi
stat_loop()
{
trap "wait; exit" SIGTERM
local filepath=$1
local expected=$2
local got
while :; do
got=$(stat -c %b $filepath)
if [ $got -ne $expected ]; then
echo -n "ERROR: unexpected used blocks"
echo " (got: $got expected: $expected)"
fi
done
}
mkfs.btrfs -f $DEV > /dev/null
# mkfs.xfs -f $DEV > /dev/null
# mkfs.ext4 -F $DEV > /dev/null
# mkfs.f2fs -f $DEV > /dev/null
# mkfs.reiserfs -f $DEV > /dev/null
mount $DEV $MNT
touch $MNT/foobar
write_size=$((64 * 1024))
for ((i = 0; i < 16384; i++)); do
offset=$(($i * $write_size))
xfs_io -c "pwrite -S 0xab $offset $write_size" $MNT/foobar >/dev/null
blocks_used=$(stat -c %b $MNT/foobar)
# Fsync the file to trigger writeback and keep calling stat(2) on it
# to see if the number of blocks used changes.
stat_loop $MNT/foobar $blocks_used &
loop_pid=$!
xfs_io -c "fsync" $MNT/foobar
kill $loop_pid &> /dev/null
wait $loop_pid
done
umount $DEV
$ ./reproducer-2.sh
ERROR: unexpected used blocks (got: 265472 expected: 265344)
ERROR: unexpected used blocks (got: 284032 expected: 283904)
(...)
Note that since this is a short time window where the race can happen, the
reproducer may not be able to always trigger the bug in one run, or it may
trigger it multiple times.
-> Case 3
Another case where such problems happen is during other operations that
replace extents in a file range with other extents. Those operations are
extent cloning, deduplication and fallocate's zero range operation.
The cause of the problem is similar to the first case. When we drop the
extents from a range, we decrement the inode's number of bytes, and later
on, after inserting the new extents we increment it. Since this is not
done atomically, a concurrent stat(2) call can see and return a number of
used blocks that is smaller than it should be, does not match the number
of used blocks before or after the clone/deduplication/zero operation.
Like for the first case, when doing a clone, deduplication or zero range
operation against an entire file, we end up having a time window where we
can report 0 used blocks to a stat(2) call.
Example reproducer:
$ cat reproducer-3.sh
#!/bin/bash
MNT=/mnt/sdi
DEV=/dev/sdi
mkfs.btrfs -f $DEV > /dev/null
# mkfs.xfs -f -m reflink=1 $DEV > /dev/null
mount $DEV $MNT
extent_size=$((64 * 1024))
num_extents=16384
file_size=$(($extent_size * $num_extents))
# File foo has many small extents.
xfs_io -f -s -c "pwrite -S 0xab -b $extent_size 0 $file_size" $MNT/foo \
> /dev/null
# File bar has much less extents and has exactly the same data as foo.
xfs_io -f -c "pwrite -S 0xab 0 $file_size" $MNT/bar > /dev/null
expected=$(stat -c %b $MNT/foo)
# Now deduplicate bar into foo. While the deduplication is in progres,
# the number of used blocks/file size reported by stat should not change
xfs_io -c "dedupe $MNT/bar 0 0 $file_size" $MNT/foo > /dev/null &
dedupe_pid=$!
while [ -n "$(ps -p $dedupe_pid -o pid=)" ]; do
used=$(stat -c %b $MNT/foo)
if [ $used -ne $expected ]; then
echo "Unexpected blocks used: $used (expected: $expected)"
fi
done
umount $DEV
$ ./reproducer-3.sh
Unexpected blocks used: 2076800 (expected: 2097152)
Unexpected blocks used: 2097024 (expected: 2097152)
Unexpected blocks used: 2079872 (expected: 2097152)
(...)
Note that since this is a short time window where the race can happen, the
reproducer may not be able to always trigger the bug in one run, or it may
trigger it multiple times.
So fix this by:
1) Making btrfs_drop_extents() not decrement the VFS inode's number of
bytes, and instead return the number of bytes;
2) Making any code that drops extents and adds new extents update the
inode's number of bytes atomically, while holding the btrfs inode's
spinlock, which is also used by the stat(2) callback to get the inode's
number of bytes;
3) For ranges in the inode's iotree that are marked as 'delalloc new',
corresponding to previously unallocated ranges, increment the inode's
number of bytes when clearing the 'delalloc new' bit from the range,
in the same critical section that decrements the inode's
'new_delalloc_bytes' counter, delimited by the btrfs inode's spinlock.
An alternative would be to have btrfs_getattr() wait for any IO (ordered
extents in progress) and locking the whole range (0 to (u64)-1) while it
it computes the number of blocks used. But that would mean blocking
stat(2), which is a very used syscall and expected to be fast, waiting
for writes, clone/dedupe, fallocate, page reads, fiemap, etc.
CC: stable@vger.kernel.org # 5.4+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
There are many arguments for __btrfs_drop_extents() and its wrapper
btrfs_drop_extents(), which makes it hard to add more arguments to it and
requires changing every caller. I have added a couple myself back in 2014
commit 1acae57b161e ("Btrfs: faster file extent item replace operations")
and therefore know firsthand that it is a bit cumbersome to add additional
arguments to these functions.
Since I will need to add more arguments in a subsequent bug fix, this
change is preparatory work and adds a data structure that holds all the
arguments, for both input and output, that are passed to this function,
with some comments in the structure's definition mentioning what each
field is and how it relates to other fields.
Callers of this function need only to zero out the content of the
structure and setup only the fields they need. This also removes the
need to have both __btrfs_drop_extents() and btrfs_drop_extents(), so
now we have a single function named btrfs_drop_extents() that takes a
pointer to this new data structure (struct btrfs_drop_extents_args).
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
