From: Dave Chinner <david@fromorbit.com>
To: Christoph Hellwig <hch@lst.de>
Cc: viro@zeniv.linux.org.uk, xfs@oss.sgi.com
Subject: Re: [PATCH 5/6] xfs: move non-inline symlinks to the pagecache
Date: Fri, 24 Apr 2015 08:29:42 +1000 [thread overview]
Message-ID: <20150423222942.GK15810@dastard> (raw)
In-Reply-To: <1429816064-10033-6-git-send-email-hch@lst.de>
On Thu, Apr 23, 2015 at 09:07:43PM +0200, Christoph Hellwig wrote:
> We can use the generic symlink in pagecache code for XFS non-inline
> symlinks. Because links are always shorter than a page we will
> get the zero termination for the link for free.
Doesn't work for v5 filesystems where headers and CRCs are embedded
into the same blocks as the symlink data. i.e. this now falls down
to ->readpage to read the link data into the page cache, and that
just reads the entire blocks into the page cache. So what we can end
up within the page cache is this:
4k block/page
+---|--------------+
hdr symlink data
And for a 1k block size v5 filesystem it could be this within a 4k
page:
1k block 1k block
+---|--------------+----|---------------+
hdr symlink data hdr symlink data
Either way, it will be completely misinterpretted by the generic
symlink code...
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
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next prev parent reply other threads:[~2015-04-23 22:29 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-23 19:07 optimize symlink handling Christoph Hellwig
2015-04-23 19:07 ` [PATCH 2/6] xfs: factor out a helper to initialize a local format inode fork Christoph Hellwig
2015-04-23 19:07 ` [PATCH 3/6] xfs: set up inode operation vectors later Christoph Hellwig
2015-04-23 19:07 ` [PATCH 4/6] xfs: use ->readlink to implement the readlink_by_handle ioctl Christoph Hellwig
2015-04-23 19:07 ` [PATCH 5/6] xfs: move non-inline symlinks to the pagecache Christoph Hellwig
2015-04-23 22:29 ` Dave Chinner [this message]
2015-04-24 8:21 ` Christoph Hellwig
2015-04-25 14:16 ` Christoph Hellwig
2015-04-25 14:57 ` Al Viro
2015-04-25 15:11 ` Al Viro
2015-04-25 18:32 ` Christoph Hellwig
2015-04-25 21:05 ` Al Viro
2015-04-23 19:07 ` [PATCH 6/6] xfs: optimize inline symlinks Christoph Hellwig
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