xfs: I/O completion handlers must use NOFS allocations

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@lst.de>
Reported-by: Thomas Neumann <tneumann@users.sourceforge.net>
Tested-by: Thomas Neumann <tneumann@users.sourceforge.net>
Reviewed-by: Alex Elder <aelder@sgi.com>
Signed-off-by: Alex Elder <aelder@sgi.com>

5 files changed, 15 insertions, 7 deletions

diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
index 2d0b3e1da9e6..6f83f58c099f 100644
--- 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);
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 67ae5555a30a..7294abce6ef2 100644
--- 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,
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 8b6c9e807efb..4d509f742bd2 100644
--- 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) {
diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
index 66b849358e62..237badcbac3b 100644
--- 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;
diff --git a/fs/xfs/xfs_trans.h b/fs/xfs/xfs_trans.h
index ed47fc77759c..a0574f593f52 100644
--- 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);