From: Yongpeng Yang Date: Tue, 10 Mar 2026 09:36:14 +0000 (+0800) Subject: f2fs: fix data loss caused by incorrect use of nat_entry flag X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=238e14eb7226f883b72caccd2d37bf5707df066b;p=thirdparty%2Fkernel%2Flinux.git f2fs: fix data loss caused by incorrect use of nat_entry flag Data loss can occur when fsync is performed on a newly created file (before any checkpoint has been written) concurrently with a checkpoint operation. The scenario is as follows: create & write & fsync 'file A' write checkpoint - f2fs_do_sync_file // inline inode - f2fs_write_inode // inode folio is dirty - f2fs_write_checkpoint - f2fs_flush_merged_writes - f2fs_sync_node_pages - f2fs_flush_nat_entries - f2fs_fsync_node_pages // no dirty node - f2fs_need_inode_block_update // return false SPO and lost 'file A' f2fs_flush_nat_entries() sets the IS_CHECKPOINTED and HAS_LAST_FSYNC flags for the nat_entry, but this does not mean that the checkpoint has actually completed successfully. However, f2fs_need_inode_block_update() checks these flags and incorrectly assumes that the checkpoint has finished. The root cause is that the semantics of IS_CHECKPOINTED and HAS_LAST_FSYNC are only guaranteed after the checkpoint write fully completes. This patch modifies f2fs_need_inode_block_update() to acquire the sbi->node_write lock before reading the nat_entry flags, ensuring that once IS_CHECKPOINTED and HAS_LAST_FSYNC are observed to be set, the checkpoint operation has already completed. Fixes: e05df3b115e7 ("f2fs: add node operations") Signed-off-by: Yongpeng Yang Reviewed-by: Chao Yu Signed-off-by: Jaegeuk Kim --- diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c index a9cd2803e681..662a61306ec6 100644 --- a/fs/f2fs/node.c +++ b/fs/f2fs/node.c @@ -427,7 +427,9 @@ bool f2fs_need_inode_block_update(struct f2fs_sb_info *sbi, nid_t ino) struct f2fs_nm_info *nm_i = NM_I(sbi); struct nat_entry *e; bool need_update = true; + struct f2fs_lock_context lc; + f2fs_down_read_trace(&sbi->node_write, &lc); f2fs_down_read(&nm_i->nat_tree_lock); e = __lookup_nat_cache(nm_i, ino, false); if (e && get_nat_flag(e, HAS_LAST_FSYNC) && @@ -435,6 +437,7 @@ bool f2fs_need_inode_block_update(struct f2fs_sb_info *sbi, nid_t ino) get_nat_flag(e, HAS_FSYNCED_INODE))) need_update = false; f2fs_up_read(&nm_i->nat_tree_lock); + f2fs_up_read_trace(&sbi->node_write, &lc); return need_update; }