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[PATCH 19/19] xfs: fix locking for inode cache radix tree tag updates

To: stable@xxxxxxxxxx
Subject: [PATCH 19/19] xfs: fix locking for inode cache radix tree tag updates
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Fri, 12 Mar 2010 09:42:17 +1100
Cc: xfs@xxxxxxxxxxx
In-reply-to: <1268347337-7160-1-git-send-email-david@xxxxxxxxxxxxx>
References: <1268347337-7160-1-git-send-email-david@xxxxxxxxxxxxx>
From: Christoph Hellwig <hch@xxxxxxxxxxxxx>

>From f1f724e4b523d444c5a598d74505aefa3d6844d2
Date: Mon, 1 Mar 2010 11:30:31 +0000
The radix-tree code requires it's users to serialize tag updates
against other updates to the tree.  While XFS protects tag updates
against each other it does not serialize them against updates of the
tree contents, which can lead to tag corruption.  Fix the inode
cache to always take pag_ici_lock in exclusive mode when updating
radix tree tags.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reported-by: Patrick Schreurs <patrick@xxxxxxxxxxxxxxxx>
Tested-by: Patrick Schreurs <patrick@xxxxxxxxxxxxxxxx>
Signed-off-by: Alex Elder <aelder@xxxxxxx>
---
 fs/xfs/linux-2.6/xfs_sync.c |    4 ++--
 fs/xfs/xfs_iget.c           |   19 +++++++++++++------
 2 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/fs/xfs/linux-2.6/xfs_sync.c b/fs/xfs/linux-2.6/xfs_sync.c
index a80371e..c1b7154 100644
--- a/fs/xfs/linux-2.6/xfs_sync.c
+++ b/fs/xfs/linux-2.6/xfs_sync.c
@@ -692,12 +692,12 @@ xfs_inode_set_reclaim_tag(
        xfs_mount_t     *mp = ip->i_mount;
        xfs_perag_t     *pag = xfs_get_perag(mp, ip->i_ino);
 
-       read_lock(&pag->pag_ici_lock);
+       write_lock(&pag->pag_ici_lock);
        spin_lock(&ip->i_flags_lock);
        __xfs_inode_set_reclaim_tag(pag, ip);
        __xfs_iflags_set(ip, XFS_IRECLAIMABLE);
        spin_unlock(&ip->i_flags_lock);
-       read_unlock(&pag->pag_ici_lock);
+       write_unlock(&pag->pag_ici_lock);
        xfs_put_perag(mp, pag);
 }
 
diff --git a/fs/xfs/xfs_iget.c b/fs/xfs/xfs_iget.c
index 40e8775..a04a72f 100644
--- a/fs/xfs/xfs_iget.c
+++ b/fs/xfs/xfs_iget.c
@@ -228,13 +228,12 @@ xfs_iget_cache_hit(
                xfs_itrace_exit_tag(ip, "xfs_iget.alloc");
 
                /*
-                * We need to set XFS_INEW atomically with clearing the
-                * reclaimable tag so that we do have an indicator of the
-                * inode still being initialized.
+                * We need to set XFS_IRECLAIM to prevent xfs_reclaim_inode
+                * from stomping over us while we recycle the inode.  We can't
+                * clear the radix tree reclaimable tag yet as it requires
+                * pag_ici_lock to be held exclusive.
                 */
-               ip->i_flags |= XFS_INEW;
-               ip->i_flags &= ~XFS_IRECLAIMABLE;
-               __xfs_inode_clear_reclaim_tag(mp, pag, ip);
+               ip->i_flags |= XFS_IRECLAIM;
 
                spin_unlock(&ip->i_flags_lock);
                read_unlock(&pag->pag_ici_lock);
@@ -253,7 +252,15 @@ xfs_iget_cache_hit(
                        __xfs_inode_set_reclaim_tag(pag, ip);
                        goto out_error;
                }
+
+               write_lock(&pag->pag_ici_lock);
+               spin_lock(&ip->i_flags_lock);
+               ip->i_flags &= ~(XFS_IRECLAIMABLE | XFS_IRECLAIM);
+               ip->i_flags |= XFS_INEW;
+               __xfs_inode_clear_reclaim_tag(mp, pag, ip);
                inode->i_state = I_LOCK|I_NEW;
+               spin_unlock(&ip->i_flags_lock);
+               write_unlock(&pag->pag_ici_lock);
        } else {
                /* If the VFS inode is being torn down, pause and try again. */
                if (!igrab(inode)) {
-- 
1.6.5

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