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@lst.de>

diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 3011b87..0a80543 100644 (file)
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -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