From: Suparna Bhattacharya <suparna@in.ibm.com>
The current implementation of O_SYNC support for AIO calls sync_page_range
explicitly in the high level aio write handlers after invoking the fops
aio_write method. This a duplication of logic across sync i/o and aio (not
good from a maintenance perspective, and more error prone, e.g. forgets to
check for O_DIRECT).
More importantly, it doesn't take into account the possibility that different
filesystems may have their own O_SYNC implementations in their corresponding
aio methods. This is a problem for example in the case of ext3 which may
commit the journal after data and meta-data are written out.
This patch fixes the above problems by moving the call to sync_page_range out
of the high level aio_pwrite handler, and back into generic_file_aio_write
for both aio and sync i/o. It takes care to make sure that sync_page_range
is called only after all the data is copied in the AIO case, rather than on
every retry.
25-akpm/fs/aio.c | 36 ++++++++++--------------------------
25-akpm/mm/filemap.c | 16 ++++++++++++++++
2 files changed, 26 insertions(+), 26 deletions(-)
diff -puN fs/aio.c~aio-O_SYNC-fix fs/aio.c
--- 25/fs/aio.c~aio-O_SYNC-fix Tue Jul 8 16:07:39 2003
+++ 25-akpm/fs/aio.c Tue Jul 8 16:07:41 2003
@@ -1289,11 +1289,6 @@ static ssize_t aio_pwrite(struct kiocb *
struct inode *inode = mapping->host;
ssize_t ret = 0;
- if (!iocb->ki_buf) {
- ret = iocb->ki_left;
- goto retry_osync;
- }
-
ret = file->f_op->aio_write(iocb, iocb->ki_buf,
iocb->ki_left, iocb->ki_pos);
@@ -1302,7 +1297,7 @@ static ssize_t aio_pwrite(struct kiocb *
* for a balance_dirty_pages to complete
*/
if (ret > 0) {
- iocb->ki_buf += ret;
+ iocb->ki_buf += iocb->ki_buf ? ret : 0;
iocb->ki_left -= ret;
ret = -EIOCBRETRY;
@@ -1312,30 +1307,19 @@ static ssize_t aio_pwrite(struct kiocb *
/* No need to retry anymore unless we need to osync data */
if (ret == 0) {
ret = iocb->ki_nbytes - iocb->ki_left;
- /* Set things up for potential O_SYNC */
- iocb->ki_buf = NULL;
- iocb->ki_pos -= ret; /* back up fpos */
- iocb->ki_left = ret; /* sync only what we have written out */
- iocb->ki_nbytes = ret;
- }
+ if (!iocb->ki_buf)
+ return ret;
-
-retry_osync:
- if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
- ssize_t err;
-
- err = sync_page_range(inode, mapping, iocb->ki_pos, ret);
- if (err <= 0) {
- ret = err;
- } else {
- BUG_ON(err > iocb->ki_left);
- iocb->ki_pos += err;
- iocb->ki_left -= err;
+ /* Set things up for potential O_SYNC */
+ if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
+ iocb->ki_buf = NULL;
+ iocb->ki_pos -= ret; /* back up fpos */
+ iocb->ki_left = ret; /* sync what we have written out */
+ iocb->ki_nbytes = ret;
ret = -EIOCBRETRY;
}
}
- if (ret == 0)
- ret = iocb->ki_nbytes - iocb->ki_left;
+
return ret;
}
diff -puN mm/filemap.c~aio-O_SYNC-fix mm/filemap.c
--- 25/mm/filemap.c~aio-O_SYNC-fix Tue Jul 8 16:07:39 2003
+++ 25-akpm/mm/filemap.c Tue Jul 8 16:07:41 2003
@@ -1911,17 +1911,33 @@ ssize_t generic_file_aio_write(struct ki
BUG_ON(iocb->ki_pos != pos);
+ if (!buf && !is_sync_kiocb(iocb)) {
+ /* nothing to transfer, may just need to sync data */
+ ret = count;
+ goto osync;
+ }
+
down(&inode->i_sem);
ret = generic_file_aio_write_nolock(iocb, &local_iov, 1,
&iocb->ki_pos);
up(&inode->i_sem);
+ /*
+ * Avoid doing a sync in parts for aio - its more efficient to
+ * call in again after all the data has been copied
+ */
+ if (!is_sync_kiocb(iocb))
+ return ret;
+
+osync:
if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
ssize_t err;
err = sync_page_range(inode, mapping, pos, ret);
if (err < 0)
ret = err;
+ else
+ iocb->ki_pos = pos + err;
}
return ret;
}
_