[PATCH 3/5] xfs: reduce ilock hold times in xfs_setattr_size

We do not need the ilock for most checks done in the beginning of
xfs_setattr_size.  Replace the long critical section before starting the
transaction with a smaller one around xfs_zero_eof and an optional one
inside xfs_qm_dqattach that isn't entered unless using quotas.  While
this isn't a big optimization for xfs_setattr_size itself it will allow
pushing the ilock into xfs_zero_eof itself later.

Signed-off-by: Christoph Hellwig <hch@...>

---
 fs/xfs/xfs_iops.c |   14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

Index: xfs/fs/xfs/xfs_iops.c
===================================================================
--- xfs.orig/fs/xfs/xfs_iops.c 2012-03-26 15:17:47.088854526 +0200
+++ xfs/fs/xfs/xfs_iops.c 2012-03-26 15:17:57.265521382 +0200
@@ -700,7 +700,7 @@ xfs_setattr_size(
  xfs_off_t oldsize, newsize;
  struct xfs_trans *tp;
  int error;
- uint lock_flags;
+ uint lock_flags = 0;
  uint commit_flags = 0;
 
  trace_xfs_setattr(ip);
@@ -720,10 +720,10 @@ xfs_setattr_size(
  ATTR_MTIME_SET|ATTR_KILL_SUID|ATTR_KILL_SGID|
  ATTR_KILL_PRIV|ATTR_TIMES_SET)) == 0);
 
- lock_flags = XFS_ILOCK_EXCL;
- if (!(flags & XFS_ATTR_NOLOCK))
+ if (!(flags & XFS_ATTR_NOLOCK)) {
  lock_flags |= XFS_IOLOCK_EXCL;
- xfs_ilock(ip, lock_flags);
+ xfs_ilock(ip, lock_flags);
+ }
 
  oldsize = inode->i_size;
  newsize = iattr->ia_size;
@@ -746,7 +746,7 @@ xfs_setattr_size(
  /*
  * Make sure that the dquots are attached to the inode.
  */
- error = xfs_qm_dqattach_locked(ip, 0);
+ error = xfs_qm_dqattach(ip, 0);
  if (error)
  goto out_unlock;
 
@@ -764,12 +764,12 @@ xfs_setattr_size(
  * before the inode is joined to the transaction to modify
  * i_size.
  */
+ xfs_ilock(ip, XFS_ILOCK_EXCL);
  error = xfs_zero_eof(ip, newsize, oldsize);
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
  if (error)
  goto out_unlock;
  }
- xfs_iunlock(ip, XFS_ILOCK_EXCL);
- lock_flags &= ~XFS_ILOCK_EXCL;
 
  /*
  * We are going to log the inode size change in this transaction so

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