Commit 17879e8f authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Dave Chinner

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: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarDave Chinner <dchinner@redhat.com>
Signed-off-by: default avatarDave Chinner <david@fromorbit.com>
parent a7d73fe6
...@@ -714,24 +714,11 @@ xfs_file_dax_write( ...@@ -714,24 +714,11 @@ xfs_file_dax_write(
struct address_space *mapping = iocb->ki_filp->f_mapping; struct address_space *mapping = iocb->ki_filp->f_mapping;
struct inode *inode = mapping->host; struct inode *inode = mapping->host;
struct xfs_inode *ip = XFS_I(inode); struct xfs_inode *ip = XFS_I(inode);
struct xfs_mount *mp = ip->i_mount;
ssize_t ret = 0; ssize_t ret = 0;
int unaligned_io = 0; int iolock = XFS_IOLOCK_EXCL;
int iolock;
struct iov_iter data; 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); xfs_rw_ilock(ip, iolock);
ret = xfs_file_aio_write_checks(iocb, from, &iolock); ret = xfs_file_aio_write_checks(iocb, from, &iolock);
if (ret) if (ret)
goto out; goto out;
...@@ -758,11 +745,6 @@ xfs_file_dax_write( ...@@ -758,11 +745,6 @@ xfs_file_dax_write(
WARN_ON_ONCE(ret); 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); trace_xfs_file_dax_write(ip, iov_iter_count(from), iocb->ki_pos);
data = *from; data = *from;
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment