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From:   David Howells <dhowells@redhat.com>
To:     torvalds@linux-foundation.org
cc:     dhowells@redhat.com, Andrew W Elble <aweits@rit.edu>,
        Jeff Layton <jlayton@kernel.org>,
        "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        Al Viro <viro@zeniv.linux.org.uk>, ceph-devel@vger.kernel.org,
        linux-afs@lists.infradead.org, linux-cachefs@redhat.com,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [GIT PULL] netfs, afs: Fix write_begin/end
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Date:   Mon, 21 Jun 2021 21:41:02 +0100
Message-ID: <2842348.1624308062@warthog.procyon.org.uk>
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Hi Linus,

Could you pull this please?  It includes patches to fix netfs_write_begin(=
)
and afs_write_end() in the following ways:

 (1) In netfs_write_begin(), extract the decision about whether to skip a
     page out to its own helper and have that clear around the region to b=
e
     written, but not clear that region.  This requires the filesystem to
     patch it up afterwards if the hole doesn't get completely filled.

 (2) Use offset_in_thp() in (1) rather than manually calculating the offse=
t
     into the page.

 (3) Due to (1), afs_write_end() now needs to handle short data write into
     the page by generic_perform_write().  I've adopted an analogous
     approach to ceph of just returning 0 in this case and letting the
     caller go round again.

It also adds a note that (in the future) the len parameter may extend
beyond the page allocated.  This is because the page allocation is deferre=
d
to write_begin() and that gets to decide what size of THP to allocate.

Thanks,
David

Link: https://lore.kernel.org/r/20210613233345.113565-1-jlayton@kernel.org=
/
Link: https://lore.kernel.org/r/162367681795.460125.11729955608839747375.s=
tgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/162391823192.1173366.9740514875196345746.s=
tgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/162429000639.2770648.6368710175435880749.s=
tgit@warthog.procyon.org.uk/ # v3

Changes
=3D=3D=3D=3D=3D=3D=3D

ver #3:
   - Drop the bits that make afs take account of len exceeding the end of
     the page in afs_write_begin/end().

ver #2:
   - Removed a var that's no longer used (spotted by the kernel test robot=
)
   - Removed a forgotten "noinline".

ver #1:
   - Prefixed the Jeff's new helper with "netfs_".
   - Don't call zero_user_segments() for a full-page write.
   - Altered the beyond-last-page check to avoid a DIV.
   - Removed redundant zero-length-file check.
   - Added patches to fix afs.

---
The following changes since commit 009c9aa5be652675a06d5211e1640e02bbb1c33=
d:

  Linux 5.13-rc6 (2021-06-13 14:43:10 -0700)

are available in the Git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git tags=
/netfs-fixes-20210621

for you to fetch changes up to 827a746f405d25f79560c7868474aec5aee174e1:

  netfs: fix test for whether we can skip read when writing beyond EOF (20=
21-06-21 21:24:07 +0100)

----------------------------------------------------------------
netfslib fixes

----------------------------------------------------------------
David Howells (1):
      afs: Fix afs_write_end() to handle short writes

Jeff Layton (1):
      netfs: fix test for whether we can skip read when writing beyond EOF

 fs/afs/write.c         | 11 +++++++++--
 fs/netfs/read_helper.c | 49 ++++++++++++++++++++++++++++++++++++---------=
----
 2 files changed, 45 insertions(+), 15 deletions(-)