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SubjectFw: [PATCH][2.6-mm] More AIO O_SYNC related fixes
----- Forwarded message from Suparna Bhattacharya <suparna@in.ibm.com> -----

Date: Tue, 26 Aug 2003 12:04:33 +0530
From: Suparna Bhattacharya <suparna@in.ibm.com>
To: akpm@osdl.org
Subject: [PATCH][2.6-mm] More AIO O_SYNC related fixes
Reply-To: suparna@in.ibm.com

The attached patch plugs some inaccuracies and associated
inefficiencies in sync_page_range handling for AIO
O_SYNC writes.

- Correctly propagate the return value from sync_page_range
when some but not all pages in the range have completed
writeback (Otherwise, O_SYNC AIO writes could report
completion before all the relevant writeouts actually
completed)
- Reset and check page dirty settings prior to attempting
writeouts to avoid blocking synchronously for a writeback
initiated otherwise.
- Disable repeated calls to writeout or generic_osync_inode
during AIO retries for the same iocb.
- Don't block synchronously for data writeouts to complete
when writing out inode state for generic_osync_inode in
AIO context. The wait_on_page_range call after this will
take care of completing the iocb only after the data has
been written out. [TBD: Is this particular change OK for
data=ordered, or does it need rethinking ?]

I have run aio-stress with modifications for AIO O_SYNC
writes on ext2, ext3, jfs, xfs and blockdev.

Regards
Suparna
--
Suparna Bhattacharya (suparna@in.ibm.com)
Linux Technology Center
IBM Software Labs, India


diff -ur -X dontdiff pure-mm3/fs/fs-writeback.c linux-2.6.0-test3-mm1/fs/fs-writeback.c
--- pure-mm3/fs/fs-writeback.c Mon Aug 25 16:59:50 2003
+++ linux-2.6.0-test3-mm1/fs/fs-writeback.c Mon Aug 25 20:47:34 2003
@@ -162,7 +162,7 @@
if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC))
write_inode(inode, wait);

- if (wait)
+ if (wait && !in_aio())
filemap_fdatawait(mapping);

spin_lock(&inode_lock);
diff -ur -X dontdiff pure-mm3/include/linux/aio.h linux-2.6.0-test3-mm1/include/linux/aio.h
--- pure-mm3/include/linux/aio.h Mon Aug 25 17:00:40 2003
+++ linux-2.6.0-test3-mm1/include/linux/aio.h Wed Aug 20 16:31:53 2003
@@ -29,21 +29,26 @@
#define KIF_LOCKED 0
#define KIF_KICKED 1
#define KIF_CANCELLED 2
+#define KIF_SYNCED 3

#define kiocbTryLock(iocb) test_and_set_bit(KIF_LOCKED, &(iocb)->ki_flags)
#define kiocbTryKick(iocb) test_and_set_bit(KIF_KICKED, &(iocb)->ki_flags)
+#define kiocbTrySync(iocb) test_and_set_bit(KIF_SYNCED, &(iocb)->ki_flags)

#define kiocbSetLocked(iocb) set_bit(KIF_LOCKED, &(iocb)->ki_flags)
#define kiocbSetKicked(iocb) set_bit(KIF_KICKED, &(iocb)->ki_flags)
#define kiocbSetCancelled(iocb) set_bit(KIF_CANCELLED, &(iocb)->ki_flags)
+#define kiocbSetSynced(iocb) set_bit(KIF_SYNCED, &(iocb)->ki_flags)

#define kiocbClearLocked(iocb) clear_bit(KIF_LOCKED, &(iocb)->ki_flags)
#define kiocbClearKicked(iocb) clear_bit(KIF_KICKED, &(iocb)->ki_flags)
#define kiocbClearCancelled(iocb) clear_bit(KIF_CANCELLED, &(iocb)->ki_flags)
+#define kiocbClearSynced(iocb) clear_bit(KIF_SYNCED, &(iocb)->ki_flags)

#define kiocbIsLocked(iocb) test_bit(KIF_LOCKED, &(iocb)->ki_flags)
#define kiocbIsKicked(iocb) test_bit(KIF_KICKED, &(iocb)->ki_flags)
#define kiocbIsCancelled(iocb) test_bit(KIF_CANCELLED, &(iocb)->ki_flags)
+#define kiocbIsSynced(iocb) test_bit(KIF_SYNCED, &(iocb)->ki_flags)

struct kiocb {
struct list_head ki_run_list;
diff -ur -X dontdiff pure-mm3/mm/filemap.c linux-2.6.0-test3-mm1/mm/filemap.c
--- pure-mm3/mm/filemap.c Mon Aug 25 16:59:28 2003
+++ linux-2.6.0-test3-mm1/mm/filemap.c Mon Aug 25 20:48:45 2003
@@ -1950,13 +1944,9 @@

osync:
if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
- ssize_t err;
-
- err = sync_page_range_nolock(inode, mapping, pos, ret);
- if (err < 0)
- ret = err;
- else
- *ppos = pos + err;
+ ret = sync_page_range_nolock(inode, mapping, pos, ret);
+ if (ret >= 0)
+ *ppos = pos + ret;
}
return ret;
}
@@ -2020,13 +2012,9 @@

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;
+ ret = sync_page_range(inode, mapping, pos, ret);
+ if (ret >= 0)
+ iocb->ki_pos = pos + ret;
}
return ret;
}
diff -ur -X dontdiff pure-mm3/mm/page-writeback.c linux-2.6.0-test3-mm1/mm/page-writeback.c
--- pure-mm3/mm/page-writeback.c Mon Aug 25 16:59:35 2003
+++ linux-2.6.0-test3-mm1/mm/page-writeback.c Mon Aug 25 20:49:55 2003
@@ -641,6 +641,10 @@
.nr_to_write = 1,
};

+ if (!test_clear_page_dirty(page)) {
+ unlock_page(page);
+ return 0;
+ }
wait_on_page_writeback(page);
return page->mapping->a_ops->writepage(page, &wbc);
}
@@ -662,8 +666,13 @@
ssize_t sync_page_range(struct inode *inode, struct address_space *mapping,
loff_t pos, size_t count)
{
- int ret;
+ int ret = 0;

+ if (in_aio()) {
+ /* Already issued writeouts for this iocb ? */
+ if (kiocbTrySync(io_wait_to_kiocb(current->io_wait)))
+ goto do_wait; /* just need to check if done */
+ }
if (!mapping->a_ops->writepage)
return 0;
if (mapping->backing_dev_info->memory_backed)
@@ -674,6 +683,7 @@
ret = generic_osync_inode(inode, OSYNC_METADATA);
up(&inode->i_sem);
}
+do_wait:
if (ret >= 0)
ret = wait_on_page_range(mapping, pos, count);
return ret;
@@ -688,8 +698,13 @@
ssize_t sync_page_range_nolock(struct inode *inode, struct address_space
*mapping, loff_t pos, size_t count)
{
- int ret;
+ ssize_t ret = 0;

+ if (in_aio()) {
+ /* Already issued writeouts for this iocb ? */
+ if (kiocbTrySync(io_wait_to_kiocb(current->io_wait)))
+ goto do_wait; /* just need to check if done */
+ }
if (!mapping->a_ops->writepage)
return 0;
if (mapping->backing_dev_info->memory_backed)
@@ -698,6 +713,7 @@
if (ret >= 0) {
ret = generic_osync_inode(inode, OSYNC_METADATA);
}
+do_wait:
if (ret >= 0)
ret = wait_on_page_range(mapping, pos, count);
return ret;

----- End forwarded message -----
--
Suparna Bhattacharya (suparna@in.ibm.com)
Linux Technology Center
IBM Software Labs, India

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