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[PATCH 1/5 v3] xfs: always take the iolock around xfs_setattr_size

To: xfs@xxxxxxxxxxx
Subject: [PATCH 1/5 v3] xfs: always take the iolock around xfs_setattr_size
From: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Date: Mon, 14 Oct 2013 07:09:35 -0700
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20131012075639.940898263@xxxxxxxxxxxxxxxxxxxxxx>
References: <20131012075503.370510641@xxxxxxxxxxxxxxxxxxxxxx> <20131012075639.940898263@xxxxxxxxxxxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
There is no reason to conditionally take the iolock inside xfs_setattr_size
when we can let the caller handle it unconditionally, which just incrases
the lock hold time for the case where it was previously taken internally
by a few instructions.

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

---
 fs/xfs/xfs_bmap_util.c |    3 +--
 fs/xfs/xfs_file.c      |    2 +-
 fs/xfs/xfs_iops.c      |   39 +++++++++++++++++++++------------------
 fs/xfs/xfs_iops.h      |    2 +-
 4 files changed, 24 insertions(+), 22 deletions(-)

Index: xfs/fs/xfs/xfs_file.c
===================================================================
--- xfs.orig/fs/xfs/xfs_file.c  2013-10-11 20:05:38.272512388 +0200
+++ xfs/fs/xfs/xfs_file.c       2013-10-14 16:07:38.316153285 +0200
@@ -852,7 +852,7 @@ xfs_file_fallocate(
 
                iattr.ia_valid = ATTR_SIZE;
                iattr.ia_size = new_size;
-               error = -xfs_setattr_size(ip, &iattr, XFS_ATTR_NOLOCK);
+               error = -xfs_setattr_size(ip, &iattr);
        }
 
 out_unlock:
Index: xfs/fs/xfs/xfs_iops.c
===================================================================
--- xfs.orig/fs/xfs/xfs_iops.c  2013-10-11 20:05:38.272512388 +0200
+++ xfs/fs/xfs/xfs_iops.c       2013-10-14 15:28:38.900097685 +0200
@@ -709,8 +709,7 @@ out_dqrele:
 int
 xfs_setattr_size(
        struct xfs_inode        *ip,
-       struct iattr            *iattr,
-       int                     flags)
+       struct iattr            *iattr)
 {
        struct xfs_mount        *mp = ip->i_mount;
        struct inode            *inode = VFS_I(ip);
@@ -733,15 +732,11 @@ xfs_setattr_size(
        if (error)
                return XFS_ERROR(error);
 
+       ASSERT(xfs_isilocked(ip, XFS_IOLOCK_EXCL));
        ASSERT(S_ISREG(ip->i_d.di_mode));
        ASSERT((mask & (ATTR_UID|ATTR_GID|ATTR_ATIME|ATTR_ATIME_SET|
                        ATTR_MTIME_SET|ATTR_KILL_PRIV|ATTR_TIMES_SET)) == 0);
 
-       if (!(flags & XFS_ATTR_NOLOCK)) {
-               lock_flags |= XFS_IOLOCK_EXCL;
-               xfs_ilock(ip, lock_flags);
-       }
-
        oldsize = inode->i_size;
        newsize = iattr->ia_size;
 
@@ -750,12 +745,11 @@ xfs_setattr_size(
         */
        if (newsize == 0 && oldsize == 0 && ip->i_d.di_nextents == 0) {
                if (!(mask & (ATTR_CTIME|ATTR_MTIME)))
-                       goto out_unlock;
+                       return 0;
 
                /*
                 * Use the regular setattr path to update the timestamps.
                 */
-               xfs_iunlock(ip, lock_flags);
                iattr->ia_valid &= ~ATTR_SIZE;
                return xfs_setattr_nonsize(ip, iattr, 0);
        }
@@ -765,7 +759,7 @@ xfs_setattr_size(
         */
        error = xfs_qm_dqattach(ip, 0);
        if (error)
-               goto out_unlock;
+               return error;
 
        /*
         * Now we can make the changes.  Before we join the inode to the
@@ -783,7 +777,7 @@ xfs_setattr_size(
                 */
                error = xfs_zero_eof(ip, newsize, oldsize);
                if (error)
-                       goto out_unlock;
+                       return error;
        }
 
        /*
@@ -802,7 +796,7 @@ xfs_setattr_size(
                error = -filemap_write_and_wait_range(VFS_I(ip)->i_mapping,
                                                      ip->i_d.di_size, newsize);
                if (error)
-                       goto out_unlock;
+                       return error;
        }
 
        /*
@@ -812,7 +806,7 @@ xfs_setattr_size(
 
        error = -block_truncate_page(inode->i_mapping, newsize, xfs_get_blocks);
        if (error)
-               goto out_unlock;
+               return error;
 
        tp = xfs_trans_alloc(mp, XFS_TRANS_SETATTR_SIZE);
        error = xfs_trans_reserve(tp, &M_RES(mp)->tr_itruncate, 0, 0);
@@ -916,12 +910,21 @@ out_trans_cancel:
 
 STATIC int
 xfs_vn_setattr(
-       struct dentry   *dentry,
-       struct iattr    *iattr)
+       struct dentry           *dentry,
+       struct iattr            *iattr)
 {
-       if (iattr->ia_valid & ATTR_SIZE)
-               return -xfs_setattr_size(XFS_I(dentry->d_inode), iattr, 0);
-       return -xfs_setattr_nonsize(XFS_I(dentry->d_inode), iattr, 0);
+       struct xfs_inode        *ip = XFS_I(dentry->d_inode);
+       int                     error;
+
+       if (iattr->ia_valid & ATTR_SIZE) {
+               xfs_ilock(ip, XFS_IOLOCK_EXCL);
+               error = xfs_setattr_size(ip, iattr);
+               xfs_iunlock(ip, XFS_IOLOCK_EXCL);
+       } else {
+               error = xfs_setattr_nonsize(ip, iattr, 0);
+       }
+
+       return -error;
 }
 
 STATIC int
Index: xfs/fs/xfs/xfs_bmap_util.c
===================================================================
--- xfs.orig/fs/xfs/xfs_bmap_util.c     2013-10-11 20:05:38.272512388 +0200
+++ xfs/fs/xfs/xfs_bmap_util.c  2013-10-14 16:07:38.316153285 +0200
@@ -1622,8 +1622,7 @@ xfs_change_file_space(
                iattr.ia_valid = ATTR_SIZE;
                iattr.ia_size = startoffset;
 
-               error = xfs_setattr_size(ip, &iattr,
-                                        attr_flags | XFS_ATTR_NOLOCK);
+               error = xfs_setattr_size(ip, &iattr);
                xfs_iunlock(ip, XFS_IOLOCK_EXCL);
 
                if (error)
Index: xfs/fs/xfs/xfs_iops.h
===================================================================
--- xfs.orig/fs/xfs/xfs_iops.h  2013-10-11 20:05:38.272512388 +0200
+++ xfs/fs/xfs/xfs_iops.h       2013-10-14 16:07:38.440153288 +0200
@@ -38,6 +38,6 @@ extern void xfs_setup_inode(struct xfs_i
 
 extern int xfs_setattr_nonsize(struct xfs_inode *ip, struct iattr *vap,
                               int flags);
-extern int xfs_setattr_size(struct xfs_inode *ip, struct iattr *vap, int 
flags);
+extern int xfs_setattr_size(struct xfs_inode *ip, struct iattr *vap);
 
 #endif /* __XFS_IOPS_H__ */

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