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[011/197] xfs: I/O completion handlers must use NOFS allocations

To: linux-kernel@xxxxxxxxxxxxxxx, stable@xxxxxxxxxx
Subject: [011/197] xfs: I/O completion handlers must use NOFS allocations
From: Greg KH <gregkh@xxxxxxx>
Date: Thu, 22 Apr 2010 12:07:42 -0700
Cc: stable-review@xxxxxxxxxx, torvalds@xxxxxxxxxxxxxxxxxxxx, akpm@xxxxxxxxxxxxxxxxxxxx, alan@xxxxxxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx, Christoph Hellwig <hch@xxxxxx>, Alex Elder <aelder@xxxxxxx>
In-reply-to: <20100422191857.GA13268@xxxxxxxxx>
User-agent: quilt/0.48-4.4
2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------


From: Christoph Hellwig <hch@xxxxxxxxxxxxx>

commit 80641dc66a2d6dfb22af4413227a92b8ab84c7bb upstream

When completing I/O requests we must not allow the memory allocator to
recurse into the filesystem, as we might deadlock on waiting for the
I/O completion otherwise.  The only thing currently allocating normal
GFP_KERNEL memory is the allocation of the transaction structure for
the unwritten extent conversion.  Add a memflags argument to
_xfs_trans_alloc to allow controlling the allocator behaviour.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reported-by: Thomas Neumann <tneumann@xxxxxxxxxxxxxxxxxxxxx>
Tested-by: Thomas Neumann <tneumann@xxxxxxxxxxxxxxxxxxxxx>
Reviewed-by: Alex Elder <aelder@xxxxxxx>
Signed-off-by: Alex Elder <aelder@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
---
 fs/xfs/xfs_fsops.c |    2 +-
 fs/xfs/xfs_iomap.c |    9 ++++++++-
 fs/xfs/xfs_mount.c |    2 +-
 fs/xfs/xfs_trans.c |    7 ++++---
 fs/xfs/xfs_trans.h |    2 +-
 5 files changed, 15 insertions(+), 7 deletions(-)

--- a/fs/xfs/xfs_fsops.c
+++ b/fs/xfs/xfs_fsops.c
@@ -611,7 +611,7 @@ xfs_fs_log_dummy(
        xfs_inode_t     *ip;
        int             error;
 
-       tp = _xfs_trans_alloc(mp, XFS_TRANS_DUMMY1);
+       tp = _xfs_trans_alloc(mp, XFS_TRANS_DUMMY1, KM_SLEEP);
        error = xfs_trans_reserve(tp, 0, XFS_ICHANGE_LOG_RES(mp), 0, 0, 0);
        if (error) {
                xfs_trans_cancel(tp, 0);
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -860,8 +860,15 @@ xfs_iomap_write_unwritten(
                 * set up a transaction to convert the range of extents
                 * from unwritten to real. Do allocations in a loop until
                 * we have covered the range passed in.
+                *
+                * Note that we open code the transaction allocation here
+                * to pass KM_NOFS--we can't risk to recursing back into
+                * the filesystem here as we might be asked to write out
+                * the same inode that we complete here and might deadlock
+                * on the iolock.
                 */
-               tp = xfs_trans_alloc(mp, XFS_TRANS_STRAT_WRITE);
+               xfs_wait_for_freeze(mp, SB_FREEZE_TRANS);
+               tp = _xfs_trans_alloc(mp, XFS_TRANS_STRAT_WRITE, KM_NOFS);
                tp->t_flags |= XFS_TRANS_RESERVE;
                error = xfs_trans_reserve(tp, resblks,
                                XFS_WRITE_LOG_RES(mp), 0,
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -1471,7 +1471,7 @@ xfs_log_sbcount(
        if (!xfs_sb_version_haslazysbcount(&mp->m_sb))
                return 0;
 
-       tp = _xfs_trans_alloc(mp, XFS_TRANS_SB_COUNT);
+       tp = _xfs_trans_alloc(mp, XFS_TRANS_SB_COUNT, KM_SLEEP);
        error = xfs_trans_reserve(tp, 0, mp->m_sb.sb_sectsize + 128, 0, 0,
                                        XFS_DEFAULT_LOG_COUNT);
        if (error) {
--- a/fs/xfs/xfs_trans.c
+++ b/fs/xfs/xfs_trans.c
@@ -236,19 +236,20 @@ xfs_trans_alloc(
        uint            type)
 {
        xfs_wait_for_freeze(mp, SB_FREEZE_TRANS);
-       return _xfs_trans_alloc(mp, type);
+       return _xfs_trans_alloc(mp, type, KM_SLEEP);
 }
 
 xfs_trans_t *
 _xfs_trans_alloc(
        xfs_mount_t     *mp,
-       uint            type)
+       uint            type,
+       uint            memflags)
 {
        xfs_trans_t     *tp;
 
        atomic_inc(&mp->m_active_trans);
 
-       tp = kmem_zone_zalloc(xfs_trans_zone, KM_SLEEP);
+       tp = kmem_zone_zalloc(xfs_trans_zone, memflags);
        tp->t_magic = XFS_TRANS_MAGIC;
        tp->t_type = type;
        tp->t_mountp = mp;
--- a/fs/xfs/xfs_trans.h
+++ b/fs/xfs/xfs_trans.h
@@ -924,7 +924,7 @@ typedef struct xfs_trans {
  * XFS transaction mechanism exported interfaces.
  */
 xfs_trans_t    *xfs_trans_alloc(struct xfs_mount *, uint);
-xfs_trans_t    *_xfs_trans_alloc(struct xfs_mount *, uint);
+xfs_trans_t    *_xfs_trans_alloc(struct xfs_mount *, uint, uint);
 xfs_trans_t    *xfs_trans_dup(xfs_trans_t *);
 int            xfs_trans_reserve(xfs_trans_t *, uint, uint, uint,
                                  uint, uint);


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