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btrfs: handle error in btrfs_cache_block_group 

[ Upstream commit db8fe64f9c ]

We have a BUG_ON(ret < 0) in find_free_extent from
btrfs_cache_block_group.  If we fail to allocate our ctl we'll just
panic, which is not good.  Instead just go on to another block group.
If we fail to find a block group we don't want to return ENOSPC, because
really we got a ENOMEM and that's the root of the problem.  Save our
return from btrfs_cache_block_group(), and then if we still fail to make
our allocation return that ret so we get the right error back.

Tested with inject-error.py from bcc.

Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
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: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Josef Bacik 2019-11-19 13:59:00 -05:00 committed by Greg Kroah-Hartman
parent a7ed0553b7
commit dfa25a8dc1
1 changed files with 18 additions and 2 deletions
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20
fs/btrfs/extent-tree.c
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@ -3781,6 +3781,7 @@ static noinline int find_free_extent(struct btrfs_fs_info *fs_info,
u64 flags, int delalloc)
{
int ret = 0;
int cache_block_group_error = 0;
struct btrfs_free_cluster *last_ptr = NULL;
struct btrfs_block_group_cache *block_group = NULL;
struct find_free_extent_ctl ffe_ctl = {0};
@ -3940,7 +3941,20 @@ have_block_group:
if (unlikely(!ffe_ctl.cached)) {
ffe_ctl.have_caching_bg = true;
ret = btrfs_cache_block_group(block_group, 0);
BUG_ON(ret < 0);
/*
* If we get ENOMEM here or something else we want to
* try other block groups, because it may not be fatal.
* However if we can't find anything else we need to
* save our return here so that we return the actual
* error that caused problems, not ENOSPC.
*/
if (ret < 0) {
if (!cache_block_group_error)
cache_block_group_error = ret;
ret = 0;
goto loop;
}
ret = 0;
}
@ -4027,7 +4041,7 @@ loop:
if (ret > 0)
goto search;
if (ret == -ENOSPC) {
if (ret == -ENOSPC && !cache_block_group_error) {
/*
* Use ffe_ctl->total_free_space as fallback if we can't find
* any contiguous hole.
@ -4038,6 +4052,8 @@ loop:
space_info->max_extent_size = ffe_ctl.max_extent_size;
spin_unlock(&space_info->lock);
ins->offset = ffe_ctl.max_extent_size;
} else if (ret == -ENOSPC) {
ret = cache_block_group_error;
}
return ret;
}