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Subject[011/197] xfs: I/O completion handlers must use NOFS allocations
2.6.32-stable review patch.  If anyone has any objections, please let us know.

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


From: Christoph Hellwig <hch@infradead.org>

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@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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
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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