From: Dmitry Monakhov <dmonakhov@openvz.org>
To: linux-kernel@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk,
hch@infradead.org, Dmitry Monakhov <dmonakhov@openvz.org>
Subject: [PATCH 0/4] fs: fcntl/fadvice fixes v2
Date: Sat, 18 Oct 2014 19:21:24 +0400 [thread overview]
Message-ID: <1413645688-13524-1-git-send-email-dmonakhov@openvz.org> (raw)
fcntl(F_SETFL) and fadvise performs direct manipulation with file's internals.
w/o notifying to fs layer. This behavior be not be suitable for some filesystems
(mostly stack-fs like ecryptfs, unionfs, etc). Let's introduce new ->set_flags()
callback for that purpose. This callback is responsible for flags check so
->check_flags() no longer required.
TOC:
fs: fcntl add set_flags wrapper -v2
fs: add fadvise file_operation
ecryptfs: add fadvise/set_flags calbacks
cifs: add set_flag callback
*OPEN ISSUE REMAINS*
This series does not fix all issues related with set_flags.
Race between fcntl(toggling O_DIRECT) vs write() is still possible
Usually O_DIRECT checked twice during call chain:
->xxx_file_write_iter
--->__generic_file_write_iter
So we may end-up up with two different values. Some filesystems (btrfs/xfs)
avoid this issue by copy-pasting __generic_file_write_iter.
One of possible way to fix this issue it to save flags in kiocb->ki_flags
as we already do with ->ki_pos. And fixup all places accordingly.
I've calculated numbers of direct access to ->f_flags it is close to 150,
half of that number is ->open() methods. So patch would not be gigantic.
And finally here is my question to AlViro and Christoph and other VFS-people:
*Are you agree with that approach?* Please say your word.
next reply other threads:[~2014-10-18 15:24 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-18 15:21 Dmitry Monakhov [this message]
2014-10-18 15:21 ` [PATCH 1/4] fs: fcntl add set_flags wrapper -v2 Dmitry Monakhov
2014-10-18 15:21 ` [PATCH 2/4] fs: add fadvise file_operation Dmitry Monakhov
2014-10-19 14:51 ` Christoph Hellwig
2014-10-21 8:31 ` Dmitry Monakhov
2014-10-18 15:21 ` [PATCH 3/4] ecryptfs: add fadvise/set_flags calbacks Dmitry Monakhov
2014-10-19 14:50 ` Christoph Hellwig
2014-10-18 15:21 ` [PATCH 4/4] cifs: add set_flag callback Dmitry Monakhov
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