[PATCH 07/10] xfs: fix locking for DAX writes

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



So far DAX writes inherited the locking from direct I/O writes, but the direct
I/O model of using shared locks for writes is actually wrong for DAX.  For
direct I/O we're out of any standards and don't have to provide the Posix
required exclusion between writers, but for DAX which gets transparently
enable on applications without any knowledge of it we can't simply drop the
requirement.  Even worse this only happens for aligned writes and thus
doesn't show up for many typical use cases.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 fs/xfs/xfs_file.c | 20 +-------------------
 1 file changed, 1 insertion(+), 19 deletions(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index e612a02..62649cc 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -714,24 +714,11 @@ xfs_file_dax_write(
 	struct address_space	*mapping = iocb->ki_filp->f_mapping;
 	struct inode		*inode = mapping->host;
 	struct xfs_inode	*ip = XFS_I(inode);
-	struct xfs_mount	*mp = ip->i_mount;
 	ssize_t			ret = 0;
-	int			unaligned_io = 0;
-	int			iolock;
+	int			iolock = XFS_IOLOCK_EXCL;
 	struct iov_iter		data;
 
-	/* "unaligned" here means not aligned to a filesystem block */
-	if ((iocb->ki_pos & mp->m_blockmask) ||
-	    ((iocb->ki_pos + iov_iter_count(from)) & mp->m_blockmask)) {
-		unaligned_io = 1;
-		iolock = XFS_IOLOCK_EXCL;
-	} else if (mapping->nrpages) {
-		iolock = XFS_IOLOCK_EXCL;
-	} else {
-		iolock = XFS_IOLOCK_SHARED;
-	}
 	xfs_rw_ilock(ip, iolock);
-
 	ret = xfs_file_aio_write_checks(iocb, from, &iolock);
 	if (ret)
 		goto out;
@@ -758,11 +745,6 @@ xfs_file_dax_write(
 		WARN_ON_ONCE(ret);
 	}
 
-	if (iolock == XFS_IOLOCK_EXCL && !unaligned_io) {
-		xfs_rw_ilock_demote(ip, XFS_IOLOCK_EXCL);
-		iolock = XFS_IOLOCK_SHARED;
-	}
-
 	trace_xfs_file_dax_write(ip, iov_iter_count(from), iocb->ki_pos);
 
 	data = *from;
-- 
2.1.4

--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html



[Index of Archives]     [Linux Ext4 Filesystem]     [Union Filesystem]     [Filesystem Testing]     [Ceph Users]     [Ecryptfs]     [AutoFS]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux Cachefs]     [Reiser Filesystem]     [Linux RAID]     [Samba]     [Device Mapper]     [CEPH Development]
  Powered by Linux