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xfs: stop using generic_file_read_iter for direct I/O 

XFS already implement it's own flushing of the pagecache because it
implements proper synchronization for direct I/O reads.  This means
calling generic_file_read_iter for direct I/O is rather useless,
as it doesn't do much but updating the atime and iocb position for
us.  This also gets rid of the buffered I/O fallback that isn't used
for XFS.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
This commit is contained in:
Christoph Hellwig 2016-07-20 11:36:57 +10:00 committed by Dave Chinner
parent bbc5a740c4
commit f1285ff0ac
1 changed files with 13 additions and 2 deletions
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15
fs/xfs/xfs_file.c
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@ -289,12 +289,17 @@ xfs_file_dio_aio_read(
struct address_space *mapping = iocb->ki_filp->f_mapping;
struct inode *inode = mapping->host;
struct xfs_inode *ip = XFS_I(inode);
loff_t isize = i_size_read(inode);
size_t count = iov_iter_count(to);
struct iov_iter data;
struct xfs_buftarg *target;
ssize_t ret = 0;
trace_xfs_file_direct_read(ip, count, iocb->ki_pos);
if (!count)
return 0; /* skip atime */
if (XFS_IS_REALTIME_INODE(ip))
target = ip->i_mount->m_rtdev_targp;
else
@ -303,7 +308,7 @@ xfs_file_dio_aio_read(
if (!IS_DAX(inode)) {
/* DIO must be aligned to device logical sector size */
if ((iocb->ki_pos | count) & target->bt_logical_sectormask) {
if (iocb->ki_pos == i_size_read(inode))
if (iocb->ki_pos == isize)
return 0;
return -EINVAL;
}
@ -354,9 +359,15 @@ xfs_file_dio_aio_read(
xfs_rw_ilock_demote(ip, XFS_IOLOCK_EXCL);
}
ret = generic_file_read_iter(iocb, to);
data = *to;
ret = mapping->a_ops->direct_IO(iocb, &data);
if (ret > 0) {
iocb->ki_pos += ret;
iov_iter_advance(to, ret);
}
xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
file_accessed(iocb->ki_filp);
return ret;
}