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  1. 24 Aug, 2010 5 commits
  3. 23 Aug, 2010 4 commits
    • Linus Torvalds's avatar
      Merge branch 'radix-tree' of git://git.kernel.org/pub/scm/linux/kernel/git/dgc/xfsdev · 9ee47476
      Linus Torvalds authored 
      * 'radix-tree' of git://git.kernel.org/pub/scm/linux/kernel/git/dgc/xfsdev:
  radix-tree: radix_tree_range_tag_if_tagged() can set incorrect tags
  radix-tree: clear all tags in radix_tree_node_rcu_free
      9ee47476
    • Linus Torvalds's avatar
      Linux 2.6.36-rc2 · 76be97c1
      Linus Torvalds authored
      76be97c1
    • Dave Chinner's avatar
      radix-tree: radix_tree_range_tag_if_tagged() can set incorrect tags · 144dcfc0
      Dave Chinner authored 
      Commit ebf8aa44 ("radix-tree:
omplement function radix_tree_range_tag_if_tagged") does not safely
set tags on on intermediate tree nodes. The code walks down the tree
setting tags before it has fully resolved the path to the leaf under
the assumption there will be a leaf slot with the tag set in the
range it is searching.

Unfortunately, this is not a valid assumption - we can abort after
setting a tag on an intermediate node if we overrun the number of
tags we are allowed to set in a batch, or stop scanning because we
we have passed the last scan index before we reach a leaf slot with
the tag we are searching for set.

As a result, we can leave the function with tags set on intemediate
nodes which can be tripped over later by tag-based lookups. The
result of these stale tags is that lookup may end prematurely or
livelock because the lookup cannot make progress.

The fix for the problem involves reocrding the traversal path we
take to the leaf nodes, and only propagating the tags back up the
tree once the tag is set in the leaf node slot. We are already
recording the path for efficient traversal, so there is no
additional overhead to do the intermediately node tag setting in
this manner.

This fixes a radix tree lookup livelock triggered by the new
writeback sync livelock avoidance code introduced in commit
f446daae ("mm: implement writeback
livelock avoidance using page tagging").
Signed-off-by: default avatarDave Chinner <dchinner@redhat.com>
Acked-by: default avatarJan Kara <jack@suse.cz>
      144dcfc0
    • Dave Chinner's avatar
      radix-tree: clear all tags in radix_tree_node_rcu_free · b6dd0865
      Dave Chinner authored 
      Commit f446daae ("mm: implement
writeback livelock avoidance using page tagging") introduced a new
radix tree tag, increasing the number of tags in each node from 2 to
3. It did not, however, fix up the code in
radix_tree_node_rcu_free() that cleans up after radix_tree_shrink()
and hence could leave stray tags set in the new tag array.

The result is that the livelock avoidance code added in the the
above commit would hit stale tags when doing tag based lookups,
resulting in livelocks when trying to traverse the tree.

Fix this problem in radix_tree_node_rcu_free() so it doesn't happen
again in the future by using a loop to walk all the tags up to
RADIX_TREE_MAX_TAGS to clear the stray tags radix_tree_shrink()
leaves behind.
Signed-off-by: default avatarDave Chinner <dchinner@redhat.com>
Acked-by: default avatarNick Piggin <npiggin@kernel.dk>
Acked-by: default avatarJan Kara <jack@suse.cz>
      b6dd0865
  5. 22 Aug, 2010 12 commits
  7. 21 Aug, 2010 6 commits
  9. 20 Aug, 2010 13 commits
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