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[GFS2] Put back O_DIRECT support

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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>
This commit is contained in:
Steven Whitehouse
2006-02-14 11:54:42 +00:00
parent fc69d0d336
commit d1665e4142
2 changed files with 75 additions and 26 deletions
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29
fs/gfs2/ops_file.c
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@@ -176,16 +176,16 @@ static ssize_t __gfs2_file_aio_read(struct kiocb *iocb,
* 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 @@ static ssize_t __gfs2_file_aio_read(struct kiocb *iocb,
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 @@ static ssize_t __gfs2_file_aio_read(struct kiocb *iocb,
goto out;
}
fallback_to_normal:
retval = 0;
if (count) {
for (seg = 0; seg < nr_segs; seg++) {