Re: 2.6.0-test9-mm3 - AIO test results

From: Suparna Bhattacharya
Date: Mon Nov 17 2003 - 00:21:50 EST


On Thu, Nov 13, 2003 at 02:03:58PM -0800, Daniel McNeil wrote:
> Andrew,
>
> I'm testing test9-mm3 on a 2-proc Xeon with a ext3 file system.
> I tested using the test programs aiocp and aiodio_sparse.
> (see http://developer.osdl.org/daniel/AIO/)
>
> Using aiocp with i/o sizes from 1k to 512k to copy files worked
> without any errors or kernel debug messages.
>
> With 64k i/o, the aiodio_sparse program complete without any errors.
> There are no kernel error messages, so that is good.
>
> There are still problems with non power of 2 i/o sizes using AIO and
> O_DIRECT. It hangs with aio's that do not seem to complete. The test
> does exit when hitting ^c and there are no kernel messages. Test output
> below:

Could you check if the following patch fixes the problem for you ?

Regards
Suparna

--------------------------------------------------------------

With this patch, when the DIO code falls back to buffered i/o after
having submitted part of the i/o, then buffered i/o is issued only
for the remaining part of the request (i.e. the part not already
covered by DIO).

diff -ur pure-mm3/fs/direct-io.c linux-2.6.0-test9-mm3/fs/direct-io.c
--- pure-mm3/fs/direct-io.c 2003-11-14 09:09:06.000000000 +0530
+++ linux-2.6.0-test9-mm3/fs/direct-io.c 2003-11-17 09:00:47.000000000 +0530
@@ -74,6 +74,7 @@
been performed at the start of a
write */
int pages_in_io; /* approximate total IO pages */
+ size_t size; /* total request size (doesn't change)*/
sector_t block_in_file; /* Current offset into the underlying
file in dio_block units. */
unsigned blocks_available; /* At block_in_file. changes */
@@ -226,7 +227,7 @@
dio_complete(dio, dio->block_in_file << dio->blkbits,
dio->result);
/* Complete AIO later if falling back to buffered i/o */
- if (dio->result != -ENOTBLK) {
+ if (dio->result >= dio->size || dio->rw == READ) {
aio_complete(dio->iocb, dio->result, 0);
kfree(dio);
} else {
@@ -889,6 +890,7 @@
dio->blkbits = blkbits;
dio->blkfactor = inode->i_blkbits - blkbits;
dio->start_zero_done = 0;
+ dio->size = 0;
dio->block_in_file = offset >> blkbits;
dio->blocks_available = 0;
dio->cur_page = NULL;
@@ -925,7 +927,7 @@

for (seg = 0; seg < nr_segs; seg++) {
user_addr = (unsigned long)iov[seg].iov_base;
- bytes = iov[seg].iov_len;
+ dio->size += bytes = iov[seg].iov_len;

/* Index into the first page of the first block */
dio->first_block_in_page = (user_addr & ~PAGE_MASK) >> blkbits;
@@ -956,6 +958,13 @@
}
} /* end iovec loop */

+ if (ret == -ENOTBLK && rw == WRITE) {
+ /*
+ * The remaining part of the request will be
+ * be handled by buffered I/O when we return
+ */
+ ret = 0;
+ }
/*
* There may be some unwritten disk at the end of a part-written
* fs-block-sized block. Go zero that now.
@@ -986,19 +995,13 @@
*/
if (dio->is_async) {
if (ret == 0)
- ret = dio->result; /* Bytes written */
- if (ret == -ENOTBLK) {
- /*
- * The request will be reissued via buffered I/O
- * when we return; Any I/O already issued
- * effectively becomes redundant.
- */
- dio->result = ret;
+ ret = dio->result;
+ if (ret > 0 && dio->result < dio->size && rw == WRITE) {
dio->waiter = current;
}
finished_one_bio(dio); /* This can free the dio */
blk_run_queues();
- if (ret == -ENOTBLK) {
+ if (dio->waiter) {
/*
* Wait for already issued I/O to drain out and
* release its references to user-space pages
@@ -1032,7 +1035,8 @@
}
dio_complete(dio, offset, ret);
/* We could have also come here on an AIO file extend */
- if (!is_sync_kiocb(iocb) && (ret != -ENOTBLK))
+ if (!is_sync_kiocb(iocb) && !(rw == WRITE && ret >= 0 &&
+ dio->result < dio->size))
aio_complete(iocb, ret, 0);
kfree(dio);
}
diff -ur pure-mm3/mm/filemap.c linux-2.6.0-test9-mm3/mm/filemap.c
--- pure-mm3/mm/filemap.c 2003-11-14 09:15:08.000000000 +0530
+++ linux-2.6.0-test9-mm3/mm/filemap.c 2003-11-15 11:11:16.000000000 +0530
@@ -1895,14 +1895,16 @@
*/
if (written >= 0 && file->f_flags & O_SYNC)
status = generic_osync_inode(inode, mapping, OSYNC_METADATA);
- if (written >= 0 && !is_sync_kiocb(iocb))
+ if (written >= count && !is_sync_kiocb(iocb))
written = -EIOCBQUEUED;
- if (written != -ENOTBLK)
+ if (written < 0 || written >= count)
goto out_status;
/*
* direct-io write to a hole: fall through to buffered I/O
+ * for completing the rest of the request.
*/
- written = 0;
+ pos += written;
+ count -= written;
}

buf = iov->iov_base;
-
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