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authorQu Wenruo <wqu@suse.com>2019-11-15 05:09:00 +0300
committerDavid Sterba <dsterba@suse.com>2019-11-18 20:07:55 +0300
commitb12de52896c0e8213f70e3a168fde9e6eee95909 (patch)
treec1241f2e70f80ed3d2326c6c1ede97642c6bc0a5 /fs/btrfs/block-group.c
parent7f0432d0d8dc1d29ab5276805d648c5b0a408105 (diff)
downloadlinux-b12de52896c0e8213f70e3a168fde9e6eee95909.tar.xz
btrfs: scrub: Don't check free space before marking a block group RO
[BUG] When running btrfs/072 with only one online CPU, it has a pretty high chance to fail: btrfs/072 12s ... _check_dmesg: something found in dmesg (see xfstests-dev/results//btrfs/072.dmesg) - output mismatch (see xfstests-dev/results//btrfs/072.out.bad) --- tests/btrfs/072.out 2019-10-22 15:18:14.008965340 +0800 +++ /xfstests-dev/results//btrfs/072.out.bad 2019-11-14 15:56:45.877152240 +0800 @@ -1,2 +1,3 @@ QA output created by 072 Silence is golden +Scrub find errors in "-m dup -d single" test ... And with the following call trace: BTRFS info (device dm-5): scrub: started on devid 1 ------------[ cut here ]------------ BTRFS: Transaction aborted (error -27) WARNING: CPU: 0 PID: 55087 at fs/btrfs/block-group.c:1890 btrfs_create_pending_block_groups+0x3e6/0x470 [btrfs] CPU: 0 PID: 55087 Comm: btrfs Tainted: G W O 5.4.0-rc1-custom+ #13 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:btrfs_create_pending_block_groups+0x3e6/0x470 [btrfs] Call Trace: __btrfs_end_transaction+0xdb/0x310 [btrfs] btrfs_end_transaction+0x10/0x20 [btrfs] btrfs_inc_block_group_ro+0x1c9/0x210 [btrfs] scrub_enumerate_chunks+0x264/0x940 [btrfs] btrfs_scrub_dev+0x45c/0x8f0 [btrfs] btrfs_ioctl+0x31a1/0x3fb0 [btrfs] do_vfs_ioctl+0x636/0xaa0 ksys_ioctl+0x67/0x90 __x64_sys_ioctl+0x43/0x50 do_syscall_64+0x79/0xe0 entry_SYSCALL_64_after_hwframe+0x49/0xbe ---[ end trace 166c865cec7688e7 ]--- [CAUSE] The error number -27 is -EFBIG, returned from the following call chain: btrfs_end_transaction() |- __btrfs_end_transaction() |- btrfs_create_pending_block_groups() |- btrfs_finish_chunk_alloc() |- btrfs_add_system_chunk() This happens because we have used up all space of btrfs_super_block::sys_chunk_array. The root cause is, we have the following bad loop of creating tons of system chunks: 1. The only SYSTEM chunk is being scrubbed It's very common to have only one SYSTEM chunk. 2. New SYSTEM bg will be allocated As btrfs_inc_block_group_ro() will check if we have enough space after marking current bg RO. If not, then allocate a new chunk. 3. New SYSTEM bg is still empty, will be reclaimed During the reclaim, we will mark it RO again. 4. That newly allocated empty SYSTEM bg get scrubbed We go back to step 2, as the bg is already mark RO but still not cleaned up yet. If the cleaner kthread doesn't get executed fast enough (e.g. only one CPU), then we will get more and more empty SYSTEM chunks, using up all the space of btrfs_super_block::sys_chunk_array. [FIX] Since scrub/dev-replace doesn't always need to allocate new extent, especially chunk tree extent, so we don't really need to do chunk pre-allocation. To break above spiral, here we introduce a new parameter to btrfs_inc_block_group(), @do_chunk_alloc, which indicates whether we need extra chunk pre-allocation. For relocation, we pass @do_chunk_alloc=true, while for scrub, we pass @do_chunk_alloc=false. This should keep unnecessary empty chunks from popping up for scrub. Also, since there are two parameters for btrfs_inc_block_group_ro(), add more comment for it. Reviewed-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs/block-group.c')
-rw-r--r--fs/btrfs/block-group.c48
1 files changed, 31 insertions, 17 deletions
diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index d96561d1ce90..6934a5b8708f 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -2017,8 +2017,17 @@ static u64 update_block_group_flags(struct btrfs_fs_info *fs_info, u64 flags)
return flags;
}
-int btrfs_inc_block_group_ro(struct btrfs_block_group *cache)
-
+/*
+ * Mark one block group RO, can be called several times for the same block
+ * group.
+ *
+ * @cache: the destination block group
+ * @do_chunk_alloc: whether need to do chunk pre-allocation, this is to
+ * ensure we still have some free space after marking this
+ * block group RO.
+ */
+int btrfs_inc_block_group_ro(struct btrfs_block_group *cache,
+ bool do_chunk_alloc)
{
struct btrfs_fs_info *fs_info = cache->fs_info;
struct btrfs_trans_handle *trans;
@@ -2048,25 +2057,29 @@ again:
goto again;
}
- /*
- * if we are changing raid levels, try to allocate a corresponding
- * block group with the new raid level.
- */
- alloc_flags = update_block_group_flags(fs_info, cache->flags);
- if (alloc_flags != cache->flags) {
- ret = btrfs_chunk_alloc(trans, alloc_flags, CHUNK_ALLOC_FORCE);
+ if (do_chunk_alloc) {
/*
- * ENOSPC is allowed here, we may have enough space
- * already allocated at the new raid level to
- * carry on
+ * If we are changing raid levels, try to allocate a
+ * corresponding block group with the new raid level.
*/
- if (ret == -ENOSPC)
- ret = 0;
- if (ret < 0)
- goto out;
+ alloc_flags = update_block_group_flags(fs_info, cache->flags);
+ if (alloc_flags != cache->flags) {
+ ret = btrfs_chunk_alloc(trans, alloc_flags,
+ CHUNK_ALLOC_FORCE);
+ /*
+ * ENOSPC is allowed here, we may have enough space
+ * already allocated at the new raid level to carry on
+ */
+ if (ret == -ENOSPC)
+ ret = 0;
+ if (ret < 0)
+ goto out;
+ }
}
- ret = inc_block_group_ro(cache, 0);
+ ret = inc_block_group_ro(cache, !do_chunk_alloc);
+ if (!do_chunk_alloc)
+ goto unlock_out;
if (!ret)
goto out;
alloc_flags = btrfs_get_alloc_profile(fs_info, cache->space_info->flags);
@@ -2081,6 +2094,7 @@ out:
check_system_chunk(trans, alloc_flags);
mutex_unlock(&fs_info->chunk_mutex);
}
+unlock_out:
mutex_unlock(&fs_info->ro_block_group_mutex);
btrfs_end_transaction(trans);