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authorChristoph Hellwig <hch@lst.de>2016-09-19 11:24:50 +1000
committerDave Chinner <david@fromorbit.com>2016-09-19 11:24:50 +1000
commit17879e8f865f4ed8b6f9041a2687ad40f13ae460 (patch)
tree4d543b880fb8d762b4a57a4988a2099c1115428b /fs/xfs
parenta7d73fe6c538fdba42635c0b8e73382fcd4bd667 (diff)
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xfs: fix locking for DAX writes
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@lst.de> Reviewed-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Dave Chinner <david@fromorbit.com>
Diffstat (limited to 'fs/xfs')
-rw-r--r--fs/xfs/xfs_file.c20
1 files changed, 1 insertions, 19 deletions
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index e612a0233710..62649ccdbb4d 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;