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aio: report error from io_destroy() when threads race in io_destroy()

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As reported by Anatol Pomozov, io_destroy() fails to report an error when
it loses the race to destroy a given ioctx.  Since there is a difference in
behaviour between the thread that wins the race (which blocks on outstanding
io requests) versus lthe thread that loses (which returns immediately), wire
up a return code from kill_ioctx() to the io_destroy() syscall.

Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>
Cc: Anatol Pomozov <anatol.pomozov@gmail.com>
This commit is contained in:
Benjamin LaHaise 2014-04-29 12:45:17 -04:00
parent d52a8f9ead
commit fb2d448383
1 changed files with 9 additions and 7 deletions
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16
fs/aio.c
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@ -727,7 +727,7 @@ err:
* when the processes owning a context have all exited to encourage
* the rapid destruction of the kioctx.
*/
static void kill_ioctx(struct mm_struct *mm, struct kioctx *ctx,
static int kill_ioctx(struct mm_struct *mm, struct kioctx *ctx,
struct completion *requests_done)
{
if (!atomic_xchg(&ctx->dead, 1)) {
@ -759,10 +759,10 @@ static void kill_ioctx(struct mm_struct *mm, struct kioctx *ctx,
ctx->requests_done = requests_done;
percpu_ref_kill(&ctx->users);
} else {
if (requests_done)
complete(requests_done);
return 0;
}
return -EINVAL;
}
/* wait_on_sync_kiocb:
@ -1219,21 +1219,23 @@ SYSCALL_DEFINE1(io_destroy, aio_context_t, ctx)
if (likely(NULL != ioctx)) {
struct completion requests_done =
COMPLETION_INITIALIZER_ONSTACK(requests_done);
int ret;
/* Pass requests_done to kill_ioctx() where it can be set
* in a thread-safe way. If we try to set it here then we have
* a race condition if two io_destroy() called simultaneously.
*/
kill_ioctx(current->mm, ioctx, &requests_done);
ret = kill_ioctx(current->mm, ioctx, &requests_done);
percpu_ref_put(&ioctx->users);
/* Wait until all IO for the context are done. Otherwise kernel
* keep using user-space buffers even if user thinks the context
* is destroyed.
*/
wait_for_completion(&requests_done);
if (!ret)
wait_for_completion(&requests_done);
return 0;
return ret;
}
pr_debug("EINVAL: io_destroy: invalid context id\n");
return -EINVAL;