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[PATCH v6 0/4] xfs: seek_data/seek_hole refinements

To: xfs@xxxxxxxxxxx
Subject: [PATCH v6 0/4] xfs: seek_data/seek_hole refinements
From: Jeff Liu <jeff.liu@xxxxxxxxxx>
Date: Thu, 2 Aug 2012 23:10:07 -0700 (PDT)
Organization: Oracle
Reply-to: jeff.liu@xxxxxxxxxx
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.28) Gecko/20120313 Thunderbird/3.1.20
Hello,

This is the new version of supplying xfs_seek_data/xfs_seek_hole refinements by 
probing page cache
to find out the desired offset for unwritten extents.

Hi Dave,

According to your comments for v5, we have to check both page->index && 
page->mapping after locking a page due to
memory reclaim or truncate.  For page->mapping, it definitely need to check up 
again as it may be invalidated or
truncated.  For page->index, we have a reference on this page at 
pagevec_lookup(), to this point, its mapping may
be set to NULL, but it would still resides in cache or swap space IMHO, so the 
index will not change because of that.
I think I must missing something in this point, could you please give some 
hints?


Changes from v6 to v5:

- Fix off-by-one bug for calculating the number of pages to be mapped.

- Fix a few comments according to Mark and Dave's comments.

- Introduce a new helper routine xfs_lookup_buffer_offset() to lookup the 
desired offset from one page.
  This could help reducing one level of indention at xfs_find_get_pgoff().

- Verify page->mapping after page got locked at xfs_find_get_pgoff() as a 
searched page may be invalidated/truncated
  at memory reclarim or page truncation stage.

- xfs_seek_data()/xfs_seek_hole(): loop bodys are indent by one level as for if 
statements.


Old version:
 
Version 5 of this posting can be found at
http://www.spinics.net/lists/xfs/msg12987.html

Version 4 of this posting can be found at
http://oss.sgi.com/archives/xfs/2012-07/msg00279.html

Version 3 of this posting can be found at
http://oss.sgi.com/archives/xfs/2012-07/msg00050.html

Version 2 of this posting can be found at
http://oss.sgi.com/archives/xfs/2012-06/msg00407.html

Version 1 of this posting can be found at
http://www.digipedia.pl/usenet/thread/11980/26875/


Thanks,
-Jeff

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