[GFS2] Put back O_DIRECT support
This patch adds back O_DIRECT support with various caveats
attached:
1. Journaled data can be read via O_DIRECT since its now the
same on disk format as normal data files.
2. Journaled data writes with O_DIRECT will be failed sliently
back to normal writes (should we really do this I wonder or
should we return an error instead?)
3. Stuffed files will be failed back to normal buffered I/O
4. All the usual corner cases (write beyond current end of file,
write to an unallocated block) will also revert to normal buffered I/O.
The I/O path is slightly odd as reads arrive at the page cache layer
with the lock for the file already held, but writes arrive unlocked.
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
diff --git a/fs/gfs2/ops_file.c b/fs/gfs2/ops_file.c
index 56820b3..bcde7a0 100644
--- a/fs/gfs2/ops_file.c
+++ b/fs/gfs2/ops_file.c
@@ -176,16 +176,16 @@
* If any segment has a negative length, or the cumulative
* length ever wraps negative then return -EINVAL.
*/
- count += iv->iov_len;
- if (unlikely((ssize_t)(count|iv->iov_len) < 0))
- return -EINVAL;
- if (access_ok(VERIFY_WRITE, iv->iov_base, iv->iov_len))
- continue;
- if (seg == 0)
- return -EFAULT;
- nr_segs = seg;
- count -= iv->iov_len; /* This segment is no good */
- break;
+ count += iv->iov_len;
+ if (unlikely((ssize_t)(count|iv->iov_len) < 0))
+ return -EINVAL;
+ if (access_ok(VERIFY_WRITE, iv->iov_base, iv->iov_len))
+ continue;
+ if (seg == 0)
+ return -EFAULT;
+ nr_segs = seg;
+ count -= iv->iov_len; /* This segment is no good */
+ break;
}
/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
@@ -204,10 +204,14 @@
retval = gfs2_glock_nq_m_atime(1, &gh);
if (retval)
goto out;
-
+ if (gfs2_is_stuffed(ip)) {
+ gfs2_glock_dq_m(1, &gh);
+ gfs2_holder_uninit(&gh);
+ goto fallback_to_normal;
+ }
size = i_size_read(inode);
if (pos < size) {
- retval = gfs2_direct_IO_read(iocb, iov, pos, nr_segs);
+ retval = gfs2_direct_IO_read(iocb, iov, pos, nr_segs);
if (retval > 0 && !is_sync_kiocb(iocb))
retval = -EIOCBQUEUED;
if (retval > 0)
@@ -219,6 +223,7 @@
goto out;
}
+fallback_to_normal:
retval = 0;
if (count) {
for (seg = 0; seg < nr_segs; seg++) {