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From: Jens Axboe <axboe@kernel.dk>
To: io-uring@vger.kernel.org, linux-fsdevel@vger.kernel.org
Cc: torvalds@linux-foundation.org, viro@zeniv.linux.org.uk
Subject: [PATCHSET v2 0/3] Add ability to save/restore iov_iter state
Date: Tue, 14 Sep 2021 08:17:47 -0600	[thread overview]
Message-ID: <20210914141750.261568-1-axboe@kernel.dk> (raw)

Hi,

Linus didn't particularly love the iov_iter->truncated addition and how
it was used, and it was hard to disagree with that. Instead of relying
on tracking ->truncated, add a few pieces of state so we can safely
handle partial or errored read/write attempts (that we want to retry).

Then we can get rid of the iov_iter addition, and at the same time
handle cases that weren't handled correctly before.

I've run this through vectored read/write with io_uring on the commonly
problematic cases (dm and low depth SCSI device) which trigger these
conditions often, and it seems to pass muster.

For a discussion on this topic, see the thread here:

https://lore.kernel.org/linux-fsdevel/CAHk-=wiacKV4Gh-MYjteU0LwNBSGpWrK-Ov25HdqB1ewinrFPg@mail.gmail.com/

You can find these patches here:

https://git.kernel.dk/cgit/linux-block/log/?h=iov_iter.2

Changes since v1:
- Drop 'did_bytes' from iov_iter_restore(). Only two cases in io_uring
  used it, and one of them had to be changed with v2. Better to just
  make the subsequent iov_iter_advance() explicit at that point.
- Cleanup and sanitize the io_uring side, and ensure it's sane around
  worker retries. No more digging into iov_iter_state from io_uring, we
  use it just for save/restore purposes.

-- 
Jens Axboe



             reply	other threads:[~2021-09-14 14:18 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-14 14:17 Jens Axboe [this message]
2021-09-14 14:17 ` [PATCH 1/3] iov_iter: add helper to save " Jens Axboe
2021-09-14 14:17 ` [PATCH 2/3] io_uring: use iov_iter state save/restore helpers Jens Axboe
2021-09-14 18:45   ` Linus Torvalds
2021-09-14 19:37     ` Jens Axboe
2021-09-14 23:02       ` Jens Axboe
2021-09-14 14:17 ` [PATCH 3/3] Revert "iov_iter: track truncated size" Jens Axboe

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