Messages in this thread Patch in this message | | | Date | Fri, 10 Oct 2003 17:18:21 +0530 | From | Suparna Bhattacharya <> | Subject | Re: 2.6.0-test6-mm4 - oops in __aio_run_iocbs() |
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On Fri, Oct 10, 2003 at 02:04:01PM +0530, Suparna Bhattacharya wrote: > On Thu, Oct 09, 2003 at 10:38:41AM -0700, Daniel McNeil wrote: > > On Thu, 2003-10-09 at 04:16, Suparna Bhattacharya wrote: > > > On Wed, Oct 08, 2003 at 04:18:15PM -0700, Daniel McNeil wrote: > > > > I'm been testing AIO on test6-mm4 using a ext3 file system and > > > > copying a 88MB file to an already existing preallocated file of 88MB. > > > > I been using my aiocp program to copy the file using i/o sizes of > > > > 1k to 512k and outstanding aio requests of between 1 and 64 using > > > > O_DIRECT, O_SYNC and O_DIRECT & O_SYNC. Everything works as long > > > > as the file is pre-allocated. When copying the file to a new file > > > > (O_CREAT|O_DIRECT), I get the following oops: > > > > > > What are the i/o sizes and block sizes for which you get the oops ? > > > Is this only for large i/o sizes ? > > > > > > I've done more testing and it is a little confusing. > > I originally got the oops running a shell script which copied 4 > > 88MB files one at a time to a sub-directory: > > > > for i in fff ff1 ff2 ff3 > > do > > aiocp -b 128k -n 8 -f CREAT -f DIRECT $i junkdir/$i > > done > > sync > > > > This script would always cause the oops and the machine would lock up. > > > > I ran aiocp manually using different block sizes (4k-128k) to copy > > 1 file to a subdirectory. I removed the file in the subdirectory > > afterward. These tests completed without any problems or oopses. > > > > > __aio_run_iocbs should have been called only for buffered i/o, > > > so this sounds like an O_DIRECT fallback to buffered i/o. > > > Possibly after already submitting some blocks direct to BIO, > > > the i/o completion path for which ends up calling aio_complete > > > releasing the iocb. That could explain the use-after-free situation > > > you see. > > > > mm4 has my extra iocb ref count for retries patch. So the iocb should > > not be being freed by aio_complete. The stack trace looks like the > > fault is on the ctx or ctx->runlist. > > The race I was suspecting is a different one - a case where the dio code > calls aio_complete before a fallback to buffered i/o, and the latter > queues up a retry. By the time the retry gets to run the reference to > the iocb would have gone. (your extra iocb ref count patch wouldn't > be able to guard against this - the correct solution would be to > avoid doing aio_complete if we run into -ENOTBLK i.e. when we intend > to fallback to buffered i/o). >
Could you try applying the following hack and see if it makes a difference ?
I was able to recreate an oops running aiocp with the same arguments that you mentioned on 2.6.0-test6-mm4; and that didn't seem to occur when I applied this patch.
Note: This is not a complete fix though and probably room for doing this in a cleaner way. If what I suspect is going on, we'll need more work to get there - like thinking through the case where a request spans an allocated region followed by a hole.
Regards Suparna -- Suparna Bhattacharya (suparna@in.ibm.com) Linux Technology Center IBM Software Labs, India
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AIO-DIO fix: Don't call aio_complete if we are falling back to buffered i/o
diff -urp puremm/fs/direct-io.c linux-2.6.0-test6-mm4/fs/direct-io.c --- puremm/fs/direct-io.c 2003-10-10 14:26:53.000000000 +0530 +++ linux-2.6.0-test6-mm4/fs/direct-io.c 2003-10-10 14:26:26.000000000 +0530 @@ -208,7 +208,7 @@ static struct page *dio_get_page(struct */ static void dio_complete(struct dio *dio, loff_t offset, ssize_t bytes) { - if (dio->end_io) + if (dio->end_io && dio->result != -ENOTBLK) dio->end_io(dio->inode, offset, bytes, dio->map_bh.b_private); if (dio->needs_locking) up_read(&dio->inode->i_alloc_sem); @@ -224,7 +224,8 @@ static void finished_one_bio(struct dio if (dio->is_async) { dio_complete(dio, dio->block_in_file << dio->blkbits, dio->result); - aio_complete(dio->iocb, dio->result, 0); + if (dio->result != -ENOTBLK) + aio_complete(dio->iocb, dio->result, 0); kfree(dio); } } @@ -978,6 +979,8 @@ direct_io_worker(int rw, struct kiocb *i * OK, all BIOs are submitted, so we can decrement bio_count to truly * reflect the number of to-be-processed BIOs. */ + if (ret == -ENOTBLK) + dio->result = ret; if (dio->is_async) { if (ret == 0) ret = dio->result; /* Bytes written */ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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