From 4e4488d4efd56951e6c1c0f60f1fc8e0f93b7964 Mon Sep 17 00:00:00 2001 From: Filipe Manana Date: Tue, 17 Jan 2023 11:21:38 +0000 Subject: [PATCH] btrfs: assert commit root semaphore is held when accessing backref cache 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 Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/backref.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c index 46851511b661..f846fec08c86 100644 --- a/fs/btrfs/backref.c +++ b/fs/btrfs/backref.c @@ -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); -- 2.20.1