[PATCH 069/102] xfs: reduce ilock hold times in xfs_file_aio_write_checks

Dave Chinner
2012-08-23T05:04:18Z

From: Christoph Hellwig <hch@infradead.org>

Upstream commit: 467f78992a0743e0e71729e4faa20b67b0f25289

We do not need the ilock for generic_write_checks and the i_size_read,
which are protected by i_mutex and/or iolock, so reduce the ilock
critical section to just the call to xfs_zero_eof.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
---
fs/xfs/linux-2.6/xfs_file.c | 23 +++++++++--------------
1 file changed, 9 insertions(+), 14 deletions(-)

diff --git a/fs/xfs/linux-2.6/xfs_file.c b/fs/xfs/linux-2.6/xfs_file.c
index 1dbd1d8..d0239cf 100644
--- a/fs/xfs/linux-2.6/xfs_file.c
+++ b/fs/xfs/linux-2.6/xfs_file.c
@@ -589,35 +589,31 @@ xfs_file_aio_write_checks(
struct xfs_inode *ip = XFS_I(inode);
int error = 0;

- xfs_rw_ilock(ip, XFS_ILOCK_EXCL);
restart:
error = generic_write_checks(file, pos, count, S_ISBLK(inode->i_mode));
- if (error) {
- xfs_rw_iunlock(ip, XFS_ILOCK_EXCL);
+ if (error)
return error;
- }

/*
* If the offset is beyond the size of the file, we need to zero any
* blocks that fall between the existing EOF and the start of this
* write. If zeroing is needed and we are currently holding the
- * iolock shared, we need to update it to exclusive which involves
- * dropping all locks and relocking to maintain correct locking order.
- * If we do this, restart the function to ensure all checks and values
- * are still valid.
+ * iolock shared, we need to update it to exclusive which implies
+ * having to redo all checks before.
*/
if (*pos > i_size_read(inode)) {
if (*iolock == XFS_IOLOCK_SHARED) {
- xfs_rw_iunlock(ip, XFS_ILOCK_EXCL | *iolock);
+ xfs_rw_iunlock(ip, *iolock);
*iolock = XFS_IOLOCK_EXCL;
- xfs_rw_ilock(ip, XFS_ILOCK_EXCL | *iolock);
+ xfs_rw_ilock(ip, *iolock);
goto restart;
}
+ xfs_rw_ilock(ip, XFS_ILOCK_EXCL);
error = -xfs_zero_eof(ip, *pos, i_size_read(inode));
+ xfs_rw_iunlock(ip, XFS_ILOCK_EXCL);
+ if (error)
+ return error;
}
- xfs_rw_iunlock(ip, XFS_ILOCK_EXCL);
- if (error)
- return error;

/*
* Updating the timestamps will grab the ilock again from
@@ -634,7 +630,6 @@ restart:
* people from modifying setuid and setgid binaries.
*/
return file_remove_suid(file);
-
}

/*