[PATCH 0/4] 2.6.33-rcX candidate fixes

[PATCH 0/4] 2.6.33-rcX candidate fixes

[Dave Chinner]

The first three of these patches are the respun inode reclaim fixes
adressing all of Christoph's concerns. These should be OK for merge
now, and once merged canbe backported to .31/.32.

The last patch is a fix for a new lockdep warning since 2.6.32 that
occurs during mount of an XFS filesystem. The ASSERT for the rwsem
being held is redundant now that lockdep checks for the lock already
being held/in use during lock initialisation that happens directly
after the ASSERT in XFS.

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[PATCH 1/4] xfs: reclaim inodes under a write lock

[Dave Chinner]

Make the inode tree reclaim walk exclusive to avoid races with
concurrent sync walkers and lookups. This is a version of
a patch posted by Christoph Hellwig that avoids all the code
duplication.

Signed-off-by: Dave Chinner <david@fromorbit.com>
---
 fs/xfs/linux-2.6/xfs_sync.c    |  150 ++++++++++++++++++----------------------
 fs/xfs/linux-2.6/xfs_sync.h    |    2 +-
 fs/xfs/quota/xfs_qm_syscalls.c |    2 +-
 3 files changed, 69 insertions(+), 85 deletions(-)

diff --git a/fs/xfs/linux-2.6/xfs_sync.c b/fs/xfs/linux-2.6/xfs_sync.c
index 6fed97a..2ee1265 100644
--- a/fs/xfs/linux-2.6/xfs_sync.c
+++ b/fs/xfs/linux-2.6/xfs_sync.c
@@ -65,7 +65,6 @@ xfs_inode_ag_lookup(
 	 * as the tree is sparse and a gang lookup walks to find
 	 * the number of objects requested.
 	 */
-	read_lock(&pag->pag_ici_lock);
 	if (tag == XFS_ICI_NO_TAG) {
 		nr_found = radix_tree_gang_lookup(&pag->pag_ici_root,
 				(void **)&ip, *first_index, 1);
@@ -74,7 +73,7 @@ xfs_inode_ag_lookup(
 				(void **)&ip, *first_index, 1, tag);
 	}
 	if (!nr_found)
-		goto unlock;
+		return NULL;
 
 	/*
 	 * Update the index for the next lookup. Catch overflows
@@ -84,13 +83,8 @@ xfs_inode_ag_lookup(
 	 */
 	*first_index = XFS_INO_TO_AGINO(mp, ip->i_ino + 1);
 	if (*first_index < XFS_INO_TO_AGINO(mp, ip->i_ino))
-		goto unlock;
-
+		return NULL;
 	return ip;
-
-unlock:
-	read_unlock(&pag->pag_ici_lock);
-	return NULL;
 }
 
 STATIC int
@@ -100,7 +94,8 @@ xfs_inode_ag_walk(
 	int			(*execute)(struct xfs_inode *ip,
 					   struct xfs_perag *pag, int flags),
 	int			flags,
-	int			tag)
+	int			tag,
+	int			exclusive)
 {
 	struct xfs_perag	*pag = &mp->m_perag[ag];
 	uint32_t		first_index;
@@ -114,10 +109,20 @@ restart:
 		int		error = 0;
 		xfs_inode_t	*ip;
 
+		if (exclusive)
+			write_lock(&pag->pag_ici_lock);
+		else
+			read_lock(&pag->pag_ici_lock);
 		ip = xfs_inode_ag_lookup(mp, pag, &first_index, tag);
-		if (!ip)
+		if (!ip) {
+			if (exclusive)
+				write_unlock(&pag->pag_ici_lock);
+			else
+				read_unlock(&pag->pag_ici_lock);
 			break;
+		}
 
+		/* execute releases pag->pag_ici_lock */
 		error = execute(ip, pag, flags);
 		if (error == EAGAIN) {
 			skipped++;
@@ -125,9 +130,8 @@ restart:
 		}
 		if (error)
 			last_error = error;
-		/*
-		 * bail out if the filesystem is corrupted.
-		 */
+
+		/* bail out if the filesystem is corrupted.  */
 		if (error == EFSCORRUPTED)
 			break;
 
@@ -148,7 +152,8 @@ xfs_inode_ag_iterator(
 	int			(*execute)(struct xfs_inode *ip,
 					   struct xfs_perag *pag, int flags),
 	int			flags,
-	int			tag)
+	int			tag,
+	int			exclusive)
 {
 	int			error = 0;
 	int			last_error = 0;
@@ -157,7 +162,8 @@ xfs_inode_ag_iterator(
 	for (ag = 0; ag < mp->m_sb.sb_agcount; ag++) {
 		if (!mp->m_perag[ag].pag_ici_init)
 			continue;
-		error = xfs_inode_ag_walk(mp, ag, execute, flags, tag);
+		error = xfs_inode_ag_walk(mp, ag, execute, flags, tag,
+						exclusive);
 		if (error) {
 			last_error = error;
 			if (error == EFSCORRUPTED)
@@ -181,11 +187,7 @@ xfs_sync_inode_valid(
 		return EFSCORRUPTED;
 	}
 
-	/*
-	 * If we can't get a reference on the inode, it must be in reclaim.
-	 * Leave it for the reclaim code to flush. Also avoid inodes that
-	 * haven't been fully initialised.
-	 */
+	/* If we can't get a reference on the inode, it must be in reclaim. */
 	if (!igrab(inode)) {
 		read_unlock(&pag->pag_ici_lock);
 		return ENOENT;
@@ -282,7 +284,7 @@ xfs_sync_data(
 	ASSERT((flags & ~(SYNC_TRYLOCK|SYNC_WAIT)) == 0);
 
 	error = xfs_inode_ag_iterator(mp, xfs_sync_inode_data, flags,
-				      XFS_ICI_NO_TAG);
+				      XFS_ICI_NO_TAG, 0);
 	if (error)
 		return XFS_ERROR(error);
 
@@ -304,7 +306,7 @@ xfs_sync_attr(
 	ASSERT((flags & ~SYNC_WAIT) == 0);
 
 	return xfs_inode_ag_iterator(mp, xfs_sync_inode_attr, flags,
-				     XFS_ICI_NO_TAG);
+				     XFS_ICI_NO_TAG, 0);
 }
 
 STATIC int
@@ -664,60 +666,6 @@ xfs_syncd_stop(
 	kthread_stop(mp->m_sync_task);
 }
 
-STATIC int
-xfs_reclaim_inode(
-	xfs_inode_t	*ip,
-	int		sync_mode)
-{
-	xfs_perag_t	*pag = xfs_get_perag(ip->i_mount, ip->i_ino);
-
-	/* The hash lock here protects a thread in xfs_iget_core from
-	 * racing with us on linking the inode back with a vnode.
-	 * Once we have the XFS_IRECLAIM flag set it will not touch
-	 * us.
-	 */
-	write_lock(&pag->pag_ici_lock);
-	spin_lock(&ip->i_flags_lock);
-	if (__xfs_iflags_test(ip, XFS_IRECLAIM) ||
-	    !__xfs_iflags_test(ip, XFS_IRECLAIMABLE)) {
-		spin_unlock(&ip->i_flags_lock);
-		write_unlock(&pag->pag_ici_lock);
-		return -EAGAIN;
-	}
-	__xfs_iflags_set(ip, XFS_IRECLAIM);
-	spin_unlock(&ip->i_flags_lock);
-	write_unlock(&pag->pag_ici_lock);
-	xfs_put_perag(ip->i_mount, pag);
-
-	/*
-	 * If the inode is still dirty, then flush it out.  If the inode
-	 * is not in the AIL, then it will be OK to flush it delwri as
-	 * long as xfs_iflush() does not keep any references to the inode.
-	 * We leave that decision up to xfs_iflush() since it has the
-	 * knowledge of whether it's OK to simply do a delwri flush of
-	 * the inode or whether we need to wait until the inode is
-	 * pulled from the AIL.
-	 * We get the flush lock regardless, though, just to make sure
-	 * we don't free it while it is being flushed.
-	 */
-	xfs_ilock(ip, XFS_ILOCK_EXCL);
-	xfs_iflock(ip);
-
-	/*
-	 * In the case of a forced shutdown we rely on xfs_iflush() to
-	 * wait for the inode to be unpinned before returning an error.
-	 */
-	if (!is_bad_inode(VFS_I(ip)) && xfs_iflush(ip, sync_mode) == 0) {
-		/* synchronize with xfs_iflush_done */
-		xfs_iflock(ip);
-		xfs_ifunlock(ip);
-	}
-
-	xfs_iunlock(ip, XFS_ILOCK_EXCL);
-	xfs_ireclaim(ip);
-	return 0;
-}
-
 void
 __xfs_inode_set_reclaim_tag(
 	struct xfs_perag	*pag,
@@ -763,16 +711,52 @@ STATIC int
 xfs_reclaim_inode_now(
 	struct xfs_inode	*ip,
 	struct xfs_perag	*pag,
-	int			flags)
+	int			sync_mode)
 {
-	/* ignore if already under reclaim */
-	if (xfs_iflags_test(ip, XFS_IRECLAIM)) {
-		read_unlock(&pag->pag_ici_lock);
+	/*
+	 * The radix tree lock here protects a thread in xfs_iget from racing
+	 * with us starting reclaim on the inode.  Once we have the
+	 * XFS_IRECLAIM flag set it will not touch us.
+	 */
+	spin_lock(&ip->i_flags_lock);
+	ASSERT_ALWAYS(__xfs_iflags_test(ip, XFS_IRECLAIMABLE));
+	if (__xfs_iflags_test(ip, XFS_IRECLAIM)) {
+		/* ignore as it is already under reclaim */
+		spin_unlock(&ip->i_flags_lock);
+		write_unlock(&pag->pag_ici_lock);
 		return 0;
 	}
-	read_unlock(&pag->pag_ici_lock);
+	__xfs_iflags_set(ip, XFS_IRECLAIM);
+	spin_unlock(&ip->i_flags_lock);
+	write_unlock(&pag->pag_ici_lock);
 
-	return xfs_reclaim_inode(ip, flags);
+	/*
+	 * If the inode is still dirty, then flush it out.  If the inode
+	 * is not in the AIL, then it will be OK to flush it delwri as
+	 * long as xfs_iflush() does not keep any references to the inode.
+	 * We leave that decision up to xfs_iflush() since it has the
+	 * knowledge of whether it's OK to simply do a delwri flush of
+	 * the inode or whether we need to wait until the inode is
+	 * pulled from the AIL.
+	 * We get the flush lock regardless, though, just to make sure
+	 * we don't free it while it is being flushed.
+	 */
+	xfs_ilock(ip, XFS_ILOCK_EXCL);
+	xfs_iflock(ip);
+
+	/*
+	 * In the case of a forced shutdown we rely on xfs_iflush() to
+	 * wait for the inode to be unpinned before returning an error.
+	 */
+	if (!is_bad_inode(VFS_I(ip)) && xfs_iflush(ip, sync_mode) == 0) {
+		/* synchronize with xfs_iflush_done */
+		xfs_iflock(ip);
+		xfs_ifunlock(ip);
+	}
+
+	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+	xfs_ireclaim(ip);
+	return 0;
 }
 
 int
@@ -781,5 +765,5 @@ xfs_reclaim_inodes(
 	int		mode)
 {
 	return xfs_inode_ag_iterator(mp, xfs_reclaim_inode_now, mode,
-					XFS_ICI_RECLAIM_TAG);
+					XFS_ICI_RECLAIM_TAG, 1);
 }
diff --git a/fs/xfs/linux-2.6/xfs_sync.h b/fs/xfs/linux-2.6/xfs_sync.h
index a500b4d..ea932b4 100644
--- a/fs/xfs/linux-2.6/xfs_sync.h
+++ b/fs/xfs/linux-2.6/xfs_sync.h
@@ -54,6 +54,6 @@ void __xfs_inode_clear_reclaim_tag(struct xfs_mount *mp, struct xfs_perag *pag,
 int xfs_sync_inode_valid(struct xfs_inode *ip, struct xfs_perag *pag);
 int xfs_inode_ag_iterator(struct xfs_mount *mp,
 	int (*execute)(struct xfs_inode *ip, struct xfs_perag *pag, int flags),
-	int flags, int tag);
+	int flags, int tag, int write_lock);
 
 #endif
diff --git a/fs/xfs/quota/xfs_qm_syscalls.c b/fs/xfs/quota/xfs_qm_syscalls.c
index 71af76f..873e07e 100644
--- a/fs/xfs/quota/xfs_qm_syscalls.c
+++ b/fs/xfs/quota/xfs_qm_syscalls.c
@@ -891,7 +891,7 @@ xfs_qm_dqrele_all_inodes(
 	uint		 flags)
 {
 	ASSERT(mp->m_quotainfo);
-	xfs_inode_ag_iterator(mp, xfs_dqrele_inode, flags, XFS_ICI_NO_TAG);
+	xfs_inode_ag_iterator(mp, xfs_dqrele_inode, flags, XFS_ICI_NO_TAG, 0);
 }
 
 /*------------------------------------------------------------------------*/
-- 
1.6.5

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[PATCH 2/4] xfs: Avoid inodes in reclaim when flushing from inode cache

[Dave Chinner]

THe reclaim code will handle flushing of dirty inodes before
reclaim occurs, so avoid them when determining whether an inode is
a candidate for flushing to disk when walking the radix trees.
This is based on a test patch from Christoph Hellwig.

Signed-off-by: Dave Chinner <david@fromorbit.com>
---
 fs/xfs/linux-2.6/xfs_sync.c |   31 ++++++++++++++++++-------------
 1 files changed, 18 insertions(+), 13 deletions(-)

diff --git a/fs/xfs/linux-2.6/xfs_sync.c b/fs/xfs/linux-2.6/xfs_sync.c
index 2ee1265..6946978 100644
--- a/fs/xfs/linux-2.6/xfs_sync.c
+++ b/fs/xfs/linux-2.6/xfs_sync.c
@@ -180,26 +180,31 @@ xfs_sync_inode_valid(
 	struct xfs_perag	*pag)
 {
 	struct inode		*inode = VFS_I(ip);
+	int			error = EFSCORRUPTED;
 
 	/* nothing to sync during shutdown */
-	if (XFS_FORCED_SHUTDOWN(ip->i_mount)) {
-		read_unlock(&pag->pag_ici_lock);
-		return EFSCORRUPTED;
-	}
+	if (XFS_FORCED_SHUTDOWN(ip->i_mount))
+		goto out_unlock;
 
-	/* If we can't get a reference on the inode, it must be in reclaim. */
-	if (!igrab(inode)) {
-		read_unlock(&pag->pag_ici_lock);
-		return ENOENT;
-	}
-	read_unlock(&pag->pag_ici_lock);
+	/* avoid new or reclaimable inodes. Leave for reclaim code to flush */
+	error = ENOENT;
+	if (xfs_iflags_test(ip, XFS_INEW | XFS_IRECLAIMABLE | XFS_IRECLAIM))
+		goto out_unlock;
 
-	if (is_bad_inode(inode) || xfs_iflags_test(ip, XFS_INEW)) {
+	/* If we can't grab the inode, it must on it's way to reclaim. */
+	if (!igrab(inode))
+		goto out_unlock;
+
+	if (is_bad_inode(inode)) {
 		IRELE(ip);
-		return ENOENT;
+		goto out_unlock;
 	}
 
-	return 0;
+	/* inode is valid */
+	error = 0;
+out_unlock:
+	read_unlock(&pag->pag_ici_lock);
+	return error;
 }
 
 STATIC int
-- 
1.6.5

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[PATCH 3/4] xfs: reclaim all inodes by background tree walks

[Dave Chinner]

We cannot do direct inode reclaim without taking the flush lock to
ensure that we do not reclaim an inode under IO. We check the inode
is clean before doing direct reclaim, but this is not good enough
because the inode flush code marks the inode clean once it has
copied the in-core dirty state to the backing buffer.

It is the flush lock that determines whether the inode is still
under IO, even though it is marked clean, and the inode is still
required at IO completion so we can't reclaim it even though it is
clean in core. Hence the requirement that we need to take the
flush lock even on clean inodes because this guarantees that the
inode writeback IO has completed and it is safe to reclaim the
inode.

With delayed write inode flushing, we coul dend up waiting a long
time on the flush lock even for a clean inode. The background
reclaim already handles this efficiently, so avoid all the problems
by killing the direct reclaim path altogether.

Signed-off-by: Dave Chinner <david@fromorbit.com>
---
 fs/xfs/linux-2.6/xfs_super.c |   14 ++++++--------
 1 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/fs/xfs/linux-2.6/xfs_super.c b/fs/xfs/linux-2.6/xfs_super.c
index 09783cc..384bd96 100644
--- a/fs/xfs/linux-2.6/xfs_super.c
+++ b/fs/xfs/linux-2.6/xfs_super.c
@@ -954,16 +954,14 @@ xfs_fs_destroy_inode(
 	ASSERT_ALWAYS(!xfs_iflags_test(ip, XFS_IRECLAIM));
 
 	/*
-	 * If we have nothing to flush with this inode then complete the
-	 * teardown now, otherwise delay the flush operation.
+	 * we always use background reclaim here because even if the
+	 * inode is clean, it still may be under IO and hence we have
+	 * to take the flush lock. The background reclaim path handles
+	 * this more efficiently than we can here, so simply let background
+	 * reclaim tear down all inodes.
 	 */
-	if (!xfs_inode_clean(ip)) {
-		xfs_inode_set_reclaim_tag(ip);
-		return;
-	}
-
 out_reclaim:
-	xfs_ireclaim(ip);
+	xfs_inode_set_reclaim_tag(ip);
 }
 
 /*
-- 
1.6.5

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[PATCH 4/4] xfs: Remove inode iolock held check during allocation

[Dave Chinner]

lockdep complains about a the lock not being initialised as we do
an ASSERT based check that the lock is not held before we initialise
it to catch inodes freed with the lock held.

lockdep does this check for us in the lock initialisation code, so
remove the ASSERT to stop the lockdep warning.

Signed-off-by: Dave Chinner <david@fromorbit.com>
---
 fs/xfs/xfs_iget.c |    1 -
 1 files changed, 0 insertions(+), 1 deletions(-)

diff --git a/fs/xfs/xfs_iget.c b/fs/xfs/xfs_iget.c
index fa402a6..155e798 100644
--- a/fs/xfs/xfs_iget.c
+++ b/fs/xfs/xfs_iget.c
@@ -73,7 +73,6 @@ xfs_inode_alloc(
 	ASSERT(atomic_read(&ip->i_pincount) == 0);
 	ASSERT(!spin_is_locked(&ip->i_flags_lock));
 	ASSERT(completion_done(&ip->i_flush));
-	ASSERT(!rwsem_is_locked(&ip->i_iolock.mr_lock));
 
 	mrlock_init(&ip->i_iolock, MRLOCK_BARRIER, "xfsio", ip->i_ino);
 
-- 
1.6.5

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Re: [PATCH 1/4] xfs: reclaim inodes under a write lock

[Christoph Hellwig]

On Mon, Jan 11, 2010 at 10:51:45AM +1100, Dave Chinner wrote:
> Make the inode tree reclaim walk exclusive to avoid races with
> concurrent sync walkers and lookups. This is a version of
> a patch posted by Christoph Hellwig that avoids all the code
> duplication.

looks good,


Reviewed-by: Christoph Hellwig <hch@lst.de>

FYI: I would rename xfs_reclaim_inode_now to just xfs_reclaim_inode,
but unless Alex wants to edit it let's just get the patch in for now.

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Re: [PATCH 2/4] xfs: Avoid inodes in reclaim when flushing from inode cache

[Christoph Hellwig]

On Mon, Jan 11, 2010 at 10:51:46AM +1100, Dave Chinner wrote:
> THe reclaim code will handle flushing of dirty inodes before
> reclaim occurs, so avoid them when determining whether an inode is
> a candidate for flushing to disk when walking the radix trees.
> This is based on a test patch from Christoph Hellwig.
> 
> Signed-off-by: Dave Chinner <david@fromorbit.com>

Looks good,


Reviewed-by: Christoph Hellwig <hch@lst.de>

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Re: [PATCH 3/4] xfs: reclaim all inodes by background tree walks

[Christoph Hellwig]

On Mon, Jan 11, 2010 at 10:51:47AM +1100, Dave Chinner wrote:
> We cannot do direct inode reclaim without taking the flush lock to
> ensure that we do not reclaim an inode under IO. We check the inode
> is clean before doing direct reclaim, but this is not good enough
> because the inode flush code marks the inode clean once it has
> copied the in-core dirty state to the backing buffer.
> 
> It is the flush lock that determines whether the inode is still
> under IO, even though it is marked clean, and the inode is still
> required at IO completion so we can't reclaim it even though it is
> clean in core. Hence the requirement that we need to take the
> flush lock even on clean inodes because this guarantees that the
> inode writeback IO has completed and it is safe to reclaim the
> inode.
> 
> With delayed write inode flushing, we coul dend up waiting a long
> time on the flush lock even for a clean inode. The background
> reclaim already handles this efficiently, so avoid all the problems
> by killing the direct reclaim path altogether.

Looks good,


Reviewed-by: Christoph Hellwig <hch@lst.de>

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Re: [PATCH 4/4] xfs: Remove inode iolock held check during allocation

[Christoph Hellwig]

On Mon, Jan 11, 2010 at 10:51:48AM +1100, Dave Chinner wrote:
> lockdep complains about a the lock not being initialised as we do
> an ASSERT based check that the lock is not held before we initialise
> it to catch inodes freed with the lock held.
> 
> lockdep does this check for us in the lock initialisation code, so
> remove the ASSERT to stop the lockdep warning.

Yes, checking things on the lock before it's initialized is always a bad
idea.  I think this is my fault because I moved the iolock
initialization from the inode_init_always path into the inode_init_once
path.


Reviewed-by: Christoph Hellwig <hch@lst.de>

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