From 28b4b0596343d19d140da059eee0e5c2b5328731 Mon Sep 17 00:00:00 2001
From: Long Li <leo.lilong@huawei.com>
Date: Thu, 17 Nov 2022 13:02:56 -0800
Subject: [PATCH] xfs: fix incorrect i_nlink caused by inode racing
Git-commit: 28b4b0596343d19d140da059eee0e5c2b5328731
Patch-mainline: v6.2-rc1
References: git-fixes
The following error occurred during the fsstress test:
Xfs: Assertion failed: VFS_I(ip)->i_nlink >= 2, file: fs/xfs/xfs_inode.c, line: 2452
The problem was that inode race condition causes incorrect i_nlink to be
written to disk, and then it is read into memory. Consider the following
call graph, inodes that are marked as both XFS_IFLUSHING and
XFS_IRECLAIMABLE, i_nlink will be reset to 1 and then restored to original
value in xfs_reinit_inode(). Therefore, the i_nlink of directory on disk
may be set to 1.
xfsaild
xfs_inode_item_push
xfs_iflush_cluster
xfs_iflush
xfs_inode_to_disk
xfs_iget
xfs_iget_cache_hit
xfs_iget_recycle
xfs_reinit_inode
inode_init_always
xfs_reinit_inode() needs to hold the ILOCK_EXCL as it is changing internal
inode state and can race with other RCU protected inode lookups. On the
read side, xfs_iflush_cluster() grabs the ILOCK_SHARED while under rcu +
ip->i_flags_lock, and so xfs_iflush/xfs_inode_to_disk() are protected from
racing inode updates (during transactions) by that lock.
Fixes: ff7bebeb91f8 ("xfs: refactor the inode recycling code") # goes further back than this
Signed-off-by: Long Li <leo.lilong@huawei.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Acked-by: Anthony Iliopoulos <ailiop@suse.com>
---
fs/xfs/xfs_icache.c | 6 ++++++
1 file changed, 6 insertions(+)
--- a/fs/xfs/xfs_icache.c
+++ b/fs/xfs/xfs_icache.c
@@ -392,6 +392,9 @@ xfs_iget_recycle(
trace_xfs_iget_recycle(ip);
+ if (!xfs_ilock_nowait(ip, XFS_ILOCK_EXCL))
+ return -EAGAIN;
+
/*
* We need to make it look like the inode is being reclaimed to prevent
* the actual reclaim workers from stomping over us while we recycle
@@ -405,6 +408,7 @@ xfs_iget_recycle(
ASSERT(!rwsem_is_locked(&inode->i_rwsem));
error = xfs_reinit_inode(mp, inode);
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
if (error) {
bool wake;
@@ -541,6 +545,8 @@ xfs_iget_cache_hit(
if (ip->i_flags & XFS_IRECLAIMABLE) {
/* Drops i_flags_lock and RCU read lock. */
error = xfs_iget_recycle(pag, ip);
+ if (error == -EAGAIN)
+ goto out_skip;
if (error)
return error;
} else {