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From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] file-posix: Cache lseek result for data
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To: Kevin Wolf <kwolf@redhat.com>, Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Cc: "qemu-block@nongnu.org" <qemu-block@nongnu.org>, "mreitz@redhat.com" <mreitz@redhat.com>, "eblake@redhat.com" <eblake@redhat.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>

On 24/01/19 16:42, Kevin Wolf wrote:
>> Recently Paolo asked me not to add more users of AioContext lock. Unfortunately
>> I don't understand the whole picture around it.. Doesn't this apply here?
>> https://lists.gnu.org/archive/html/qemu-devel/2018-12/msg03410.html
> I don't know. Honestly I feel nobody except Paolo knows, because we
> don't know his patches yet.

This is true.  On the other hand, the AioContext lock is only used in
some special cases around block jobs and blk_set_aio_context, and in
general the block devices already should not have any dependencies
(unless they crept in without me noticing).

In particular...

> But raw doesn't have an s->lock yet, so I
> think removing the AioContext lock involves some work on it anyway and
> adding this doesn't really change the amount of work.

... BDRVRawState doesn't have any data that changes after open, does it?
 This is why it doesn't have an s->lock.

Paolo