[PATCH 5.4 077/165] btrfs: handle error in btrfs_cache_block_group

Greg Kroah-Hartman
2020-01-11T10:25:48Z

From: Josef Bacik <josef@toxicpanda.com>

[ Upstream commit db8fe64f9ce61d1d89d3c3c34d111a43afb9f053 ]

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>
---
fs/btrfs/extent-tree.c | 20 ++++++++++++++++++--
1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index eb95ed78a18e..dc50605ecbda 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -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 @@ static noinline int find_free_extent(struct btrfs_fs_info *fs_info,
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 @@ static noinline int find_free_extent(struct btrfs_fs_info *fs_info,
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 @@ static noinline int find_free_extent(struct btrfs_fs_info *fs_info,
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;
}
--
2.20.1