| Date | Mon, 13 Dec 2010 22:46:49 +0800 | From | Wu Fengguang <> | Subject | [PATCH 03/35] writeback: prevent duplicate balance_dirty_pages_ratelimited() calls |
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When dd in 512bytes, balance_dirty_pages_ratelimited() used to be called 8 times for the same page, even if the page is only dirtied once. Fix it with a (slightly racy) PageDirty() test.
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com> --- mm/filemap.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
--- linux-next.orig/mm/filemap.c 2010-12-13 21:45:57.000000000 +0800 +++ linux-next/mm/filemap.c 2010-12-13 21:46:11.000000000 +0800 @@ -2244,6 +2244,7 @@ static ssize_t generic_perform_write(str long status = 0; ssize_t written = 0; unsigned int flags = 0; + unsigned int dirty; /* * Copies from kernel address space cannot fail (NFSD is a big user). @@ -2292,6 +2293,7 @@ again: pagefault_enable(); flush_dcache_page(page); + dirty = PageDirty(page); mark_page_accessed(page); status = a_ops->write_end(file, mapping, pos, bytes, copied, page, fsdata); @@ -2318,7 +2320,8 @@ again: pos += copied; written += copied; - balance_dirty_pages_ratelimited(mapping); + if (!dirty) + balance_dirty_pages_ratelimited(mapping); } while (iov_iter_count(i));
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