Messages in this thread | | | Date | Fri, 03 Oct 2014 12:13:39 -0600 | From | Jens Axboe <> | Subject | Re: [PATCH] aio: Fix return code of io_submit() (RFC) |
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On 2014-10-03 12:08, 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. > > 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...
We can't really feasibly fix this, is my worry. Fio does track the pending requests and does not get into a getevents() forever wait if it gets -EAGAIN on submission. But before the fix, it would loop forever in submission in -EAGAIN.
How are applications supposed to deal with ENOMEM? I think the answer here is that they can't, it would be a fatal condition. AIO must provide isn't own guarantee of progress, with a mempool or similar.
-- Jens Axboe
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