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mm: Use fixed constant in page_frag_alloc instead of size + 1
commit8644772637
upstream. This patch replaces the size + 1 value introduced with the recent fix for 1 byte allocs with a constant value. The idea here is to reduce code overhead as the previous logic would have to read size into a register, then increment it, and write it back to whatever field was being used. By using a constant we can avoid those memory reads and arithmetic operations in favor of just encoding the maximum value into the operation itself. Fixes:2c2ade8174
("mm: page_alloc: fix ref bias in page_frag_alloc() for 1-byte allocs") Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com> Signed-off-by: David S. Miller <davem@davemloft.net> Cc: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -4537,11 +4537,11 @@ void *page_frag_alloc(struct page_frag_cache *nc,
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/* Even if we own the page, we do not use atomic_set().
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* This would break get_page_unless_zero() users.
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*/
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page_ref_add(page, size);
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page_ref_add(page, PAGE_FRAG_CACHE_MAX_SIZE);
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/* reset page count bias and offset to start of new frag */
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nc->pfmemalloc = page_is_pfmemalloc(page);
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nc->pagecnt_bias = size + 1;
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nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1;
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nc->offset = size;
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}
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@ -4557,10 +4557,10 @@ void *page_frag_alloc(struct page_frag_cache *nc,
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size = nc->size;
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#endif
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/* OK, page count is 0, we can safely set it */
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set_page_count(page, size + 1);
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set_page_count(page, PAGE_FRAG_CACHE_MAX_SIZE + 1);
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/* reset page count bias and offset to start of new frag */
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nc->pagecnt_bias = size + 1;
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nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1;
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offset = size - fragsz;
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}
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