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SubjectRe: [PATCH 8/22] AIO cancellation fix
On Fri, Jul 02, 2004 at 06:30:30PM +0530, Suparna Bhattacharya wrote:
> Its been a while since I last posted the retry based AIO patches
> that I've been accumulating. Janet Morgan recently brought
> the whole patchset up-to to 2.6.7.
>
> The patchset contains modifications and fixes to the AIO core
> to support the full retry model, an implementation of AIO
> support for buffered filesystem AIO reads and O_SYNC writes
> (the latter courtesy O_SYNC speedup changes from Andrew Morton),
> an implementation of AIO reads and writes to pipes (from
> Chris Mason) and AIO poll (again from Chris Mason).
>
> Full retry infrastructure and fixes
> [1] aio-retry.patch
> [2] 4g4g-aio-hang-fix.patch
> [3] aio-retry-elevated-refcount.patch
> [4] aio-splice-runlist.patch
>
> FS AIO read
> [5] aio-wait-page.patch
> [6] aio-fs_read.patch
> [7] aio-upfront-readahead.patch
>
> AIO for pipes
> [8] aio-cancel-fix.patch

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

-----------------------------------
From: Chris Mason <mason@suse.com>

Fix for sys_io_cancel to work properly with retries when a cancel
method is specified for an iocb. Needed with pipe AIO support.

There's a bug in my aio cancel patch, aio_complete still makes an event
for cancelled iocbs. If nobody asks for this event, we effectively leak
space in the event ring buffer. I've attached a new aio_cancel patch
that just skips the event creation for canceled iocbs.


aio.c | 10 +++++++++-
1 files changed, 9 insertions(+), 1 deletion(-)
--- aio/fs/aio.c 2004-06-18 06:10:37.941166456 -0700
+++ aio-cancel-fix/fs/aio.c 2004-06-18 09:24:28.905991040 -0700
@@ -932,6 +932,13 @@ int fastcall aio_complete(struct kiocb *
if (iocb->ki_run_list.prev && !list_empty(&iocb->ki_run_list))
list_del_init(&iocb->ki_run_list);

+ /*
+ * cancelled requests don't get events, userland was given one
+ * when the event got cancelled.
+ */
+ if (kiocbIsCancelled(iocb))
+ goto put_rq;
+
ring = kmap_atomic(info->ring_pages[0], KM_IRQ1);

tail = info->tail;
@@ -964,7 +971,7 @@ int fastcall aio_complete(struct kiocb *
iocb->ki_retried,
iocb->ki_nbytes - iocb->ki_left, iocb->ki_nbytes,
iocb->ki_kicked, iocb->ki_queued, aio_run, aio_wakeups);
-
+put_rq:
/* everything turned out well, dispose of the aiocb. */
ret = __aio_put_req(ctx, iocb);

@@ -1611,6 +1618,7 @@ asmlinkage long sys_io_cancel(aio_contex
if (kiocb && kiocb->ki_cancel) {
cancel = kiocb->ki_cancel;
kiocb->ki_users ++;
+ kiocbSetCancelled(kiocb);
} else
cancel = NULL;
spin_unlock_irq(&ctx->ctx_lock);
-
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