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authorJan Kara <jack@suse.cz>2010-08-09 17:19:12 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-08-09 20:44:59 -0700
commitf446daaea9d4a420d16c606f755f3689dcb2d0ce (patch)
treebe2afc18f79aa4ff9be245b0a036aa06185b5dc4 /include
parentebf8aa44beed48cd17893a83d92a4403e5f9d9e2 (diff)
mm: implement writeback livelock avoidance using page tagging
We try to avoid livelocks of writeback when some steadily creates dirty pages in a mapping we are writing out. For memory-cleaning writeback, using nr_to_write works reasonably well but we cannot really use it for data integrity writeback. This patch tries to solve the problem. The idea is simple: Tag all pages that should be written back with a special tag (TOWRITE) in the radix tree. This can be done rather quickly and thus livelocks should not happen in practice. Then we start doing the hard work of locking pages and sending them to disk only for those pages that have TOWRITE tag set. Note: Adding new radix tree tag grows radix tree node from 288 to 296 bytes for 32-bit archs and from 552 to 560 bytes for 64-bit archs. However, the number of slab/slub items per page remains the same (13 and 7 respectively). Signed-off-by: Jan Kara <jack@suse.cz> Cc: Dave Chinner <david@fromorbit.com> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: Chris Mason <chris.mason@oracle.com> Cc: Theodore Ts'o <tytso@mit.edu> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/fs.h1
-rw-r--r--include/linux/radix-tree.h2
2 files changed, 2 insertions, 1 deletions
diff --git a/include/linux/fs.h b/include/linux/fs.h
index e5106e49bd2..488efec09d1 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -687,6 +687,7 @@ struct block_device {
*/
#define PAGECACHE_TAG_DIRTY 0
#define PAGECACHE_TAG_WRITEBACK 1
+#define PAGECACHE_TAG_TOWRITE 2
int mapping_tagged(struct address_space *mapping, int tag);
diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
index a4b00e9cca9..634b8e674ac 100644
--- a/include/linux/radix-tree.h
+++ b/include/linux/radix-tree.h
@@ -55,7 +55,7 @@ static inline int radix_tree_is_indirect_ptr(void *ptr)
/*** radix-tree API starts here ***/
-#define RADIX_TREE_MAX_TAGS 2
+#define RADIX_TREE_MAX_TAGS 3
/* root tags are stored in gfp_mask, shifted by __GFP_BITS_SHIFT */
struct radix_tree_root {