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[BUG]
With the following file extent layout, defrag would do unnecessary IO
and result more on-disk space usage.
# mkfs.btrfs -f $dev
# mount $dev $mnt
# xfs_io -f -c "pwrite 0 40m" $mnt/foobar
# sync
# xfs_io -f -c "pwrite 40m 16k" $mnt/foobar
# sync
Above command would lead to the following file extent layout:
item 6 key (257 EXTENT_DATA 0) itemoff 15816 itemsize 53
generation 7 type 1 (regular)
extent data disk byte 298844160 nr 41943040
extent data offset 0 nr 41943040 ram 41943040
extent compression 0 (none)
item 7 key (257 EXTENT_DATA 41943040) itemoff 15763 itemsize 53
generation 8 type 1 (regular)
extent data disk byte 13631488 nr 16384
extent data offset 0 nr 16384 ram 16384
extent compression 0 (none)
Which is mostly fine. We can allow the final 16K to be merged with the
previous 40M, but it's upon the end users' preference.
But if we defrag the file using the default parameters, it would result
worse file layout:
# btrfs filesystem defrag $mnt/foobar
# sync
item 6 key (257 EXTENT_DATA 0) itemoff 15816 itemsize 53
generation 7 type 1 (regular)
extent data disk byte 298844160 nr 41943040
extent data offset 0 nr 8650752 ram 41943040
extent compression 0 (none)
item 7 key (257 EXTENT_DATA 8650752) itemoff 15763 itemsize 53
generation 9 type 1 (regular)
extent data disk byte 340787200 nr 33292288
extent data offset 0 nr 33292288 ram 33292288
extent compression 0 (none)
item 8 key (257 EXTENT_DATA 41943040) itemoff 15710 itemsize 53
generation 8 type 1 (regular)
extent data disk byte 13631488 nr 16384
extent data offset 0 nr 16384 ram 16384
extent compression 0 (none)
Note the original 40M extent is still there, but a new 32M extent is
created for no benefit at all.
[CAUSE]
There is an existing check to make sure we won't defrag a large enough
extent (the threshold is by default 32M).
But the check is using the length to the end of the extent:
range_len = em->len - (cur - em->start);
/* Skip too large extent */
if (range_len >= extent_thresh)
goto next;
This means, for the first 8MiB of the extent, the range_len is always
smaller than the default threshold, and would not be defragged.
But after the first 8MiB, the remaining part would fit the requirement,
and be defragged.
Such different behavior inside the same extent caused the above problem,
and we should avoid different defrag decision inside the same extent.
[FIX]
Instead of using @range_len, just use @em->len, so that we have a
consistent decision among the same file extent.
Now with this fix, we won't touch the extent, thus not making it any
worse.
Reported-by: Filipe Manana <fdmanana@suse.com>
Fixes: 0cb5950f3f3b ("btrfs: fix deadlock when reserving space during defrag")
CC: stable@vger.kernel.org # 6.1+
Reviewed-by: Boris Burkov <boris@bur.io>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Although subpage itself is conflicting with higher folio, since subpage
(sectorsize < PAGE_SIZE and nodesize < PAGE_SIZE) means we will never
need higher order folio, there is a hidden pitfall:
- btrfs_page_*() helpers
Those helpers are an abstraction to handle both subpage and non-subpage
cases, which means we're going to pass pages pointers to those helpers.
And since those helpers are shared between data and metadata paths, it's
unavoidable to let them to handle folios, including higher order
folios).
Meanwhile for true subpage case, we should only have a single page
backed folios anyway, thus add a new ASSERT() for btrfs_subpage_assert()
to ensure that.
Also since those helpers are shared between both data and metadata, add
some extra ASSERT()s for data path to make sure we only get single page
backed folio for now.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Currently, in struct extent_map, we use an unsigned int (32 bits) to
identify the compression type of an extent and an unsigned long (64 bits
on a 64 bits platform, 32 bits otherwise) for flags. We are only using
6 different flags, so an unsigned long is excessive and we can use flags
to identify the compression type instead of using a dedicated 32 bits
field.
We can easily have tens or hundreds of thousands (or more) of extent maps
on busy and large filesystems, specially with compression enabled or many
or large files with tons of small extents. So it's convenient to have the
extent_map structure as small as possible in order to use less memory.
So remove the compression type field from struct extent_map, use flags
to identify the compression type and shorten the flags field from an
unsigned long to a u32. This saves 8 bytes (on 64 bits platforms) and
reduces the size of the structure from 136 bytes down to 128 bytes, using
now only two cache lines, and increases the number of extent maps we can
have per 4K page from 30 to 32. By using a u32 for the flags instead of
an unsigned long, we no longer use test_bit(), set_bit() and clear_bit(),
but that level of atomicity is not needed as most flags are never cleared
once set (before adding an extent map to the tree), and the ones that can
be cleared or set after an extent map is added to the tree, are always
performed while holding the write lock on the extent map tree, while the
reader holds a lock on the tree or tests for a flag that never changes
once the extent map is in the tree (such as compression flags).
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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After commit ac3c0d36a2a2 ("btrfs: make fiemap more efficient and accurate
reporting extent sharedness") we no longer need to create special extent
maps during fiemap that have a block start with the EXTENT_MAP_DELALLOC
value. So this block start value for extent maps is no longer used since
then, therefore remove it.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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The existing helper test_range_bit works in two ways, checks if the whole
range contains all the bits, or stop on the first occurrence. By adding
a specific helper for the latter case, the inner loop can be simplified
and contains fewer conditionals, making it a bit faster.
There's no caller that uses the cached state pointer so this reduces the
argument count further.
Signed-off-by: David Sterba <dsterba@suse.com>
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btrfs_realloc_node() is only used by the defrag code. Nowadays we have a
defrag.c file, so move it, and its helper close_blocks(), into defrag.c.
During the move also do a few minor cosmetic changes:
1) Change the return value of close_blocks() from int to bool;
2) Use SZ_32K instead of 32768 at close_blocks();
3) Make some variables const in btrfs_realloc_node(), 'blocksize' and
'end_slot';
4) Get rid of 'parent_nritems' variable, in both places where it was
used it could be replaced by calling btrfs_header_nritems(parent);
5) Change the type of a couple variables from int to bool;
6) Rename variable 'err' to 'ret', as that's the most common name we
use to track the return value of a function;
7) Move some variables from the top scope to the scope of the for loop
where they are used.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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The btrfs_defrag_root() function does not really belong in the
transaction.{c,h} module and as we have a defrag.{c,h} nowadays,
move it to there instead. This also allows to stop exporting
btrfs_defrag_leaves(), so we can make it static.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ rename info to fs_info for consistency ]
Signed-off-by: David Sterba <dsterba@suse.com>
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Now that all extent state bit helpers effectively take the GFP_NOFS mask
(and GFP_NOWAIT is encoded in the bits) we can remove the parameter.
This reduces stack consumption in many functions and simplifies a lot of
code.
Net effect on module on a release build:
text data bss dec hex filename
1250432 20985 16088 1287505 13a551 pre/btrfs.ko
1247074 20985 16088 1284147 139833 post/btrfs.ko
DELTA: -3358
Signed-off-by: David Sterba <dsterba@suse.com>
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The helper is used only once.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Given that wait is always set to 1, so remove the argument.
Last use of wait with 0 was in 0c304304feab ("Btrfs: remove
csum_bytes_left").
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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The header file linux/mm.h provides PAGE_ALIGN, PAGE_ALIGNED,
PAGE_ALIGN_DOWN macros. Use these macros to make code more
concise.
Signed-off-by: Yushan Zhou <katrinzhou@tencent.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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All error handling paths end to 'out', except this memory allocation
failure.
This is spurious. So branch to the error handling path also in this case.
It will add a call to:
memset(&root->defrag_progress, 0,
sizeof(root->defrag_progress));
Fixes: 6702ed490ca0 ("Btrfs: Add run time btree defrag, and an ioctl to force btree defrag")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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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>
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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>
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The argument @new_inline changes the following members of extent_map:
- em->compress_type
- EXTENT_FLAG_COMPRESSED of em->flags
However neither members makes a difference for inline extents:
- Inline extent read never use above em members
As inside btrfs_get_extent() we directly use the file extent item to
do the read.
- Inline extents are never to be split
Thus code really needs em->compress_type or that flag will never be
executed on inlined extents.
(btrfs_drop_extent_cache() would be one example)
- Fiemap no longer relies on extent maps
Recent fiemap optimization makes fiemap to search subvolume tree
directly, without using any extent map at all.
Thus those members make no difference for inline extents any more.
Furthermore such exception without much explanation is really a source
of confusion.
Thus this patch will completely remove the argument, and always set the
involved members, unifying the behavior.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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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>
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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>
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Now that the defrag code is all in one file, create a defrag.h and move
all the defrag related prototypes and helper out of ctree.h and into
defrag.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>
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This is the other big portion of defrag code that has existed in
ioctl.c. Move it to its new home in defrag.c.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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This currently exists in file.c, move it to the more natural location in
defrag.c.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
[ reformat comments ]
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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This currently has only one helper in it, and it's for tree based
defrag. We have the various defrag code in 3 different places, so
rename this to defrag.c. Followup patches will move the code into this
new file.
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>
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