Hi Kent,
On Fri, Oct 03, 2014 at 11:08:13AM -0700, Kent Overstreet wrote:
> io_submit() could return -EAGAIN on memory allocation failure when it should
> really have been returning -ENOMEM. This could confuse applications (i.e. fio)
> since -EAGAIN means "too many requests outstanding, wait until completions
> have
> been reaped" and if the application actually was tracking outstanding
> completions this wouldn't make a lot of sense.
Wouldn't it be simpler to just return an ERR_PTR with the appropriate
return code rather than move all that code around?
-ben
> NOTE:
>
> the man page seems to imply that the current behaviour (-EAGAIN on allocation
> failure) has always been the case. I don't think it makes a lot of sense, but
> this should probably be discussed more widely in case applications have
> somehow
> come to rely on the current behaviour...
>
> Signed-off-by: Kent Overstreet <k...@daterainc.com>
> Cc: Benjamin LaHaise <b...@kvack.org>
> Cc: Zach Brown <z...@zabbo.net>
> Cc: Jeff Moyer <jmo...@redhat.com>
> Cc: Jens Axboe <ax...@kernel.dk>
> Cc: Slava Pestov <s...@daterainc.com>
> ---
> fs/aio.c | 26 +++++++++++++-------------
> 1 file changed, 13 insertions(+), 13 deletions(-)
>
> diff --git a/fs/aio.c b/fs/aio.c
> index 733750096b..556547044b 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -933,23 +933,14 @@ static inline struct kiocb *aio_get_req(struct kioctx
> *ctx)
> {
> struct kiocb *req;
>
> - if (!get_reqs_available(ctx)) {
> - user_refill_reqs_available(ctx);
> - if (!get_reqs_available(ctx))
> - return NULL;
> - }
> -
> req = kmem_cache_alloc(kiocb_cachep, GFP_KERNEL|__GFP_ZERO);
> if (unlikely(!req))
> - goto out_put;
> + return NULL;
>
> percpu_ref_get(&ctx->reqs);
>
> req->ki_ctx = ctx;
> return req;
> -out_put:
> - put_reqs_available(ctx, 1);
> - return NULL;
> }
>
> static void kiocb_free(struct kiocb *req)
> @@ -1489,9 +1480,17 @@ static int io_submit_one(struct kioctx *ctx, struct
> iocb __user *user_iocb,
> return -EINVAL;
> }
>
> + if (!get_reqs_available(ctx)) {
> + user_refill_reqs_available(ctx);
> + if (!get_reqs_available(ctx))
> + return -EAGAIN;
> + }
> +
> req = aio_get_req(ctx);
> - if (unlikely(!req))
> - return -EAGAIN;
> + if (unlikely(!req)) {
> + ret = -ENOMEM;
> + goto out_put;
> + }
>
> req->ki_filp = fget(iocb->aio_fildes);
> if (unlikely(!req->ki_filp)) {
> @@ -1533,9 +1532,10 @@ static int io_submit_one(struct kioctx *ctx, struct
> iocb __user *user_iocb,
>
> return 0;
> out_put_req:
> - put_reqs_available(ctx, 1);
> percpu_ref_put(&ctx->reqs);
> kiocb_free(req);
> +out_put:
> + put_reqs_available(ctx, 1);
> return ret;
> }
>
> --
> 2.1.1
--
"Thought is the essence of where you are now."
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