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btrfs: assert commit root semaphore is held when accessing backref cache

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During fiemap, when accessing the cache that stores the sharedness of an
extent, we need to either be holding a transaction handle or the commit
root semaphore. I left comments about this in the comment that precedes
store_backref_shared_cache() and lookup_backref_shared_cache(), but have
actually not enforced it through assertions. So assert that the commit
root semaphore is held if we are not holding a transaction handle.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Filipe Manana
2023-01-17 11:21:38 +00:00
committed by David Sterba
parent 2b5463fcbd
commit 4e4488d4ef
1 changed files with 10 additions and 2 deletions
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12
fs/btrfs/backref.c
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@@ -1252,8 +1252,12 @@ static bool lookup_backref_shared_cache(struct btrfs_backref_share_check_ctx *ct
struct btrfs_root *root,
u64 bytenr, int level, bool *is_shared)
{
const struct btrfs_fs_info *fs_info = root->fs_info;
struct btrfs_backref_shared_cache_entry *entry;
if (!current->journal_info)
lockdep_assert_held(&fs_info->commit_root_sem);
if (!ctx->use_path_cache)
return false;
@@ -1288,7 +1292,7 @@ static bool lookup_backref_shared_cache(struct btrfs_backref_share_check_ctx *ct
* could be a snapshot sharing this extent buffer.
*/
if (entry->is_shared &&
entry->gen != btrfs_get_last_root_drop_gen(root->fs_info))
entry->gen != btrfs_get_last_root_drop_gen(fs_info))
return false;
*is_shared = entry->is_shared;
@@ -1318,9 +1322,13 @@ static void store_backref_shared_cache(struct btrfs_backref_share_check_ctx *ctx
struct btrfs_root *root,
u64 bytenr, int level, bool is_shared)
{
const struct btrfs_fs_info *fs_info = root->fs_info;
struct btrfs_backref_shared_cache_entry *entry;
u64 gen;
if (!current->journal_info)
lockdep_assert_held(&fs_info->commit_root_sem);
if (!ctx->use_path_cache)
return;
@@ -1336,7 +1344,7 @@ static void store_backref_shared_cache(struct btrfs_backref_share_check_ctx *ctx
ASSERT(level >= 0);
if (is_shared)
gen = btrfs_get_last_root_drop_gen(root->fs_info);
gen = btrfs_get_last_root_drop_gen(fs_info);
else
gen = btrfs_root_last_snapshot(&root->root_item);