archive mirror
 help / color / mirror / Atom feed
From: Goldwyn Rodrigues <>
Subject: [PATCH 0/10 v8] No wait AIO
Date: Thu, 11 May 2017 14:17:00 -0500	[thread overview]
Message-ID: <> (raw)

Formerly known as non-blocking AIO.

This series adds nonblocking feature to asynchronous I/O writes.
io_submit() can be delayed because of a number of reason:
 - Block allocation for files
 - Data writebacks for direct I/O
 - Sleeping because of waiting to acquire i_rwsem
 - Congested block device

The goal of the patch series is to return -EAGAIN/-EWOULDBLOCK if
any of these conditions are met. This way userspace can push most
of the write()s to the kernel to the best of its ability to complete
and if it returns -EAGAIN, can defer it to another thread.

In order to enable this, IOCB_RW_FLAG_NOWAIT is introduced in
uapi/linux/aio_abi.h. If set for aio_rw_flags, it translates to
IOCB_NOWAIT for struct iocb, REQ_NOWAIT for bio.bi_opf and IOMAP_NOWAIT for
iomap. aio_rw_flags is a new flag replacing aio_reserved1. We could
not use aio_flags because it is not currently checked for invalidity
in the kernel.

This feature is provided for direct I/O of asynchronous I/O only. I have
tested it against xfs, ext4, and btrfs while I intend to add more filesystems.
The nowait feature is for request based devices. In the future, I intend to
add support to stacked devices such as md.

Applications will have to check supportability
by sending a async direct write and any other error besides -EAGAIN
would mean it is not supported.

First two patches are prep patches into nowait I/O.

Changes since v1:
 + changed name from _NONBLOCKING to *_NOWAIT
 + filemap_range_has_page call moved to closer to (just before) calling filemap_write_and_wait_range().
 + BIO_NOWAIT limited to get_request()
 + XFS fixes 
	- included reflink 
	- use of xfs_ilock_nowait() instead of a XFS_IOLOCK_NONBLOCKING flag
	- Translate the flag through IOMAP_NOWAIT (iomap) to check for
	  block allocation for the file.
 + ext4 coding style

Changes since v2:
 + Using aio_reserved1 as aio_rw_flags instead of aio_flags
 + blk-mq support
 + xfs uptodate with kernel and reflink changes

 Changes since v3:
  + Added FS_NOWAIT, which is set if the filesystem supports NOWAIT feature.
  + Checks in generic_make_request() to make sure BIO_NOWAIT comes in
    for async direct writes only.
  + Added QUEUE_FLAG_NOWAIT, which is set if the device supports BIO_NOWAIT.
    This is added (rather not set) to block devices such as dm/md currently.

 Changes since v4:
  + Ported AIO code to use RWF_* flags. Check for RWF_* flags in

 Changes since v5:
  + Common helper for RWF flags.

 Changes since v6:
  + REQ_NOWAIT will be ignored for request based devices since they
    cannot block. So, removed QUEUE_FLAG_NOWAIT since it is not
    required in the current implementation. It will be resurrected
    when we program for stacked devices.
  + changed kiocb_rw_flags() to kiocb_set_rw_flags() in order to accomodate
    for errors. Moved checks in the function.

 Changes since v7:
  + split patches into prep so the main patches are smaller and easier
    to understand
  + All patches are reviewed or acked!


             reply	other threads:[~2017-05-11 19:17 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-11 19:17 Goldwyn Rodrigues [this message]
2017-05-11 19:17 ` [PATCH 01/10] fs: Separate out kiocb flags setup based on RWF_* flags Goldwyn Rodrigues
2017-05-11 19:17 ` [PATCH 02/10] fs: Introduce filemap_range_has_page() Goldwyn Rodrigues
     [not found] ` <>
2017-05-11 19:17   ` [PATCH 03/10] fs: Use RWF_* flags for AIO operations Goldwyn Rodrigues
2017-05-11 19:17 ` [PATCH 04/10] fs: Introduce RWF_NOWAIT Goldwyn Rodrigues
     [not found]   ` <>
2017-05-15  9:47     ` Jan Kara
2017-05-11 19:17 ` [PATCH 05/10] fs: return if direct write will trigger writeback Goldwyn Rodrigues
2017-05-11 19:17 ` [PATCH 06/10] fs: Introduce IOMAP_NOWAIT Goldwyn Rodrigues
2017-05-11 19:17 ` [PATCH 07/10] fs: return on congested block device Goldwyn Rodrigues
2017-05-11 19:17 ` [PATCH 08/10] ext4: nowait aio support Goldwyn Rodrigues
2017-05-11 19:17 ` [PATCH 09/10] xfs: " Goldwyn Rodrigues
2017-05-11 19:17 ` [PATCH 10/10] btrfs: " Goldwyn Rodrigues

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \ \ \ \ \ \ \ \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).