Linux-EFI Archive on lore.kernel.org
 help / color / Atom feed
From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: Jan Kara <jack@suse.cz>
Cc: linux-efi@vger.kernel.org, linux-btrfs@vger.kernel.org,
	yuchao0@huawei.com, linux-mm@kvack.org, clm@fb.com,
	adilger.kernel@dilger.ca, matthew.garrett@nebula.com,
	linux-nilfs@vger.kernel.org, linux-ext4@vger.kernel.org,
	devel@lists.orangefs.org, josef@toxicpanda.com,
	reiserfs-devel@vger.kernel.org, viro@zeniv.linux.org.uk,
	dsterba@suse.com, jaegeuk@kernel.org, tytso@mit.edu,
	ard.biesheuvel@linaro.org, linux-kernel@vger.kernel.org,
	linux-f2fs-devel@lists.sourceforge.net,
	linux-xfs@vger.kernel.org, jk@ozlabs.org, jack@suse.com,
	linux-fsdevel@vger.kernel.org, linux-mtd@lists.infradead.org,
	ocfs2-devel@oss.oracle.com
Subject: Re: [Ocfs2-devel] [PATCH 2/7] vfs: flush and wait for io when setting the immutable flag via SETFLAGS
Date: Mon, 24 Jun 2019 20:04:39 -0700
Message-ID: <20190625030439.GA5379@magnolia> (raw)
In-Reply-To: <20190624215817.GE1611011@magnolia>

On Mon, Jun 24, 2019 at 02:58:17PM -0700, Darrick J. Wong wrote:
> On Mon, Jun 24, 2019 at 01:37:37PM +0200, Jan Kara wrote:
> > On Fri 21-06-19 16:57:07, Darrick J. Wong wrote:
> > > From: Darrick J. Wong <darrick.wong@oracle.com>
> > > 
> > > When we're using FS_IOC_SETFLAGS to set the immutable flag on a file, we
> > > need to ensure that userspace can't continue to write the file after the
> > > file becomes immutable.  To make that happen, we have to flush all the
> > > dirty pagecache pages to disk to ensure that we can fail a page fault on
> > > a mmap'd region, wait for pending directio to complete, and hope the
> > > caller locked out any new writes by holding the inode lock.
> > > 
> > > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > 
> > Seeing the way this worked out, is there a reason to have separate
> > vfs_ioc_setflags_flush_data() instead of folding the functionality in
> > vfs_ioc_setflags_check() (possibly renaming it to
> > vfs_ioc_setflags_prepare() to indicate it does already some changes)? I
> > don't see any place that would need these two separated...
> 
> XFS needs them to be separated.
> 
> If we even /think/ that we're going to be setting the immutable flag
> then we need to grab the IOLOCK and the MMAPLOCK to prevent further
> writes while we drain all the directio writes and dirty data.  IO
> completions for the write draining can take the ILOCK, which means that
> we can't have grabbed it yet.
> 
> Next, we grab the ILOCK so we can check the new flags against the inode
> and then update the inode core.
> 
> For most filesystems I think it suffices to inode_lock and then do both,
> though.

Heh, lol, that applies to fssetxattr, not to setflags, because xfs
setflags implementation open-codes the relevant fssetxattr pieces.
So for setflags we can combine both parts into a single _prepare
function.

--D

> > > +/*
> > > + * Flush all pending IO and dirty mappings before setting S_IMMUTABLE on an
> > > + * inode via FS_IOC_SETFLAGS.  If the flush fails we'll clear the flag before
> > > + * returning error.
> > > + *
> > > + * Note: the caller should be holding i_mutex, or else be sure that
> > > + * they have exclusive access to the inode structure.
> > > + */
> > > +static inline int vfs_ioc_setflags_flush_data(struct inode *inode, int flags)
> > > +{
> > > +	int ret;
> > > +
> > > +	if (!vfs_ioc_setflags_need_flush(inode, flags))
> > > +		return 0;
> > > +
> > > +	inode_set_flags(inode, S_IMMUTABLE, S_IMMUTABLE);
> > > +	ret = inode_flush_data(inode);
> > > +	if (ret)
> > > +		inode_set_flags(inode, 0, S_IMMUTABLE);
> > > +	return ret;
> > > +}
> > 
> > Also this sets S_IMMUTABLE whenever vfs_ioc_setflags_need_flush() returns
> > true. That is currently the right thing but seems like a landmine waiting
> > to trip? So I'd just drop the vfs_ioc_setflags_need_flush() abstraction to
> > make it clear what's going on.
> 
> Ok.
> 
> --D
> 
> > 
> > 								Honza
> > -- 
> > Jan Kara <jack@suse.com>
> > SUSE Labs, CR
> 
> _______________________________________________
> Ocfs2-devel mailing list
> Ocfs2-devel@oss.oracle.com
> https://oss.oracle.com/mailman/listinfo/ocfs2-devel

  reply index

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-21 23:56 [PATCH v4 0/7] vfs: make immutable files actually immutable Darrick J. Wong
2019-06-21 23:56 ` [PATCH 1/7] mm/fs: don't allow writes to immutable files Darrick J. Wong
2019-06-24 11:13   ` Jan Kara
2019-06-21 23:57 ` [PATCH 2/7] vfs: flush and wait for io when setting the immutable flag via SETFLAGS Darrick J. Wong
2019-06-24 11:37   ` Jan Kara
2019-06-24 21:58     ` Darrick J. Wong
2019-06-25  3:04       ` Darrick J. Wong [this message]
2019-06-25  7:08         ` [Ocfs2-devel] " Jan Kara
2019-06-24 15:33   ` Jan Kara
2019-06-24 16:36     ` Darrick J. Wong
2019-06-21 23:57 ` [PATCH 3/7] vfs: flush and wait for io when setting the immutable flag via FSSETXATTR Darrick J. Wong
2019-06-21 23:57 ` [PATCH 4/7] vfs: don't allow most setxattr to immutable files Darrick J. Wong
2019-06-21 23:57 ` [PATCH 5/7] xfs: refactor setflags to use setattr code directly Darrick J. Wong
2019-06-21 23:57 ` [PATCH 6/7] xfs: clean up xfs_merge_ioc_xflags Darrick J. Wong
2019-06-21 23:57 ` [PATCH 7/7] vfs: don't allow writes to swap files Darrick J. Wong
2019-06-25 10:36 ` [PATCH v4 0/7] vfs: make immutable files actually immutable Christoph Hellwig
2019-06-25 18:03   ` Darrick J. Wong
2019-06-25 20:37     ` Andreas Dilger

Reply instructions:

You may reply publically 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:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

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

  git send-email \
    --in-reply-to=20190625030439.GA5379@magnolia \
    --to=darrick.wong@oracle.com \
    --cc=adilger.kernel@dilger.ca \
    --cc=ard.biesheuvel@linaro.org \
    --cc=clm@fb.com \
    --cc=devel@lists.orangefs.org \
    --cc=dsterba@suse.com \
    --cc=jack@suse.com \
    --cc=jack@suse.cz \
    --cc=jaegeuk@kernel.org \
    --cc=jk@ozlabs.org \
    --cc=josef@toxicpanda.com \
    --cc=linux-btrfs@vger.kernel.org \
    --cc=linux-efi@vger.kernel.org \
    --cc=linux-ext4@vger.kernel.org \
    --cc=linux-f2fs-devel@lists.sourceforge.net \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux-mtd@lists.infradead.org \
    --cc=linux-nilfs@vger.kernel.org \
    --cc=linux-xfs@vger.kernel.org \
    --cc=matthew.garrett@nebula.com \
    --cc=ocfs2-devel@oss.oracle.com \
    --cc=reiserfs-devel@vger.kernel.org \
    --cc=tytso@mit.edu \
    --cc=viro@zeniv.linux.org.uk \
    --cc=yuchao0@huawei.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-EFI Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-efi/0 linux-efi/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-efi linux-efi/ https://lore.kernel.org/linux-efi \
		linux-efi@vger.kernel.org linux-efi@archiver.kernel.org
	public-inbox-index linux-efi


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-efi


AGPL code for this site: git clone https://public-inbox.org/ public-inbox