From: David Sterba dsterba@suse.com
[ Upstream commit 748f553c3c4c4f175c6c834358632aff802d72cf ]
KCSAN reports that there's unlocked access mixed with locked access, which is technically correct but is not a bug. To avoid false alerts at least from KCSAN, add annotation and use a wrapper whenever ->full is accessed for read outside of lock.
It is used as a fast check and only advisory. In the worst case the block reserve is found !full and becomes full in the meantime, but properly handled.
Depending on the value of ->full, btrfs_block_rsv_release decides where to return the reservation, and block_rsv_release_bytes handles a NULL pointer for block_rsv and if it's not NULL then it double checks the full status under a lock.
Link: https://lore.kernel.org/linux-btrfs/CAAwBoOJDjei5Hnem155N_cJwiEkVwJYvgN-tQrw... Link: https://lore.kernel.org/linux-btrfs/YvHU/vsXd7uz5V6j@hungrycats.org Reported-by: Zygo Blaxell ce3g8jdj@umail.furryterror.org Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/btrfs/block-rsv.c | 2 +- fs/btrfs/block-rsv.h | 9 +++++++++ fs/btrfs/transaction.c | 4 ++-- 3 files changed, 12 insertions(+), 3 deletions(-)
diff --git a/fs/btrfs/block-rsv.c b/fs/btrfs/block-rsv.c index 06be0644dd37..046caf14a4bb 100644 --- a/fs/btrfs/block-rsv.c +++ b/fs/btrfs/block-rsv.c @@ -286,7 +286,7 @@ u64 btrfs_block_rsv_release(struct btrfs_fs_info *fs_info, */ if (block_rsv == delayed_rsv) target = global_rsv; - else if (block_rsv != global_rsv && !delayed_rsv->full) + else if (block_rsv != global_rsv && !btrfs_block_rsv_full(delayed_rsv)) target = delayed_rsv;
if (target && block_rsv->space_info != target->space_info) diff --git a/fs/btrfs/block-rsv.h b/fs/btrfs/block-rsv.h index 0c183709be00..578c3497a455 100644 --- a/fs/btrfs/block-rsv.h +++ b/fs/btrfs/block-rsv.h @@ -92,4 +92,13 @@ static inline void btrfs_unuse_block_rsv(struct btrfs_fs_info *fs_info, btrfs_block_rsv_release(fs_info, block_rsv, 0, NULL); }
+/* + * Fast path to check if the reserve is full, may be carefully used outside of + * locks. + */ +static inline bool btrfs_block_rsv_full(const struct btrfs_block_rsv *rsv) +{ + return data_race(rsv->full); +} + #endif /* BTRFS_BLOCK_RSV_H */ diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c index 4c87bf2abc14..49570ad23f2e 100644 --- a/fs/btrfs/transaction.c +++ b/fs/btrfs/transaction.c @@ -594,7 +594,7 @@ start_transaction(struct btrfs_root *root, unsigned int num_items, */ num_bytes = btrfs_calc_insert_metadata_size(fs_info, num_items); if (flush == BTRFS_RESERVE_FLUSH_ALL && - delayed_refs_rsv->full == 0) { + btrfs_block_rsv_full(delayed_refs_rsv) == 0) { delayed_refs_bytes = num_bytes; num_bytes <<= 1; } @@ -619,7 +619,7 @@ start_transaction(struct btrfs_root *root, unsigned int num_items, if (rsv->space_info->force_alloc) do_chunk_alloc = true; } else if (num_items == 0 && flush == BTRFS_RESERVE_FLUSH_ALL && - !delayed_refs_rsv->full) { + !btrfs_block_rsv_full(delayed_refs_rsv)) { /* * Some people call with btrfs_start_transaction(root, 0) * because they can be throttled, but have some other mechanism