Given process_checks is only called in resync path, it should be
ok to allocate three stack variable(total 320byteds) to store
pages from bios.

Signed-off-by: Ming Lei <tom.leim...@gmail.com>
---
 drivers/md/raid1.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 4400fbe7ce8c..54ec32be3277 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -2010,6 +2010,9 @@ static void process_checks(struct r1bio *r1_bio)
        int primary;
        int i;
        int vcnt;
+       struct bio_vec *bi;
+       int page_len[RESYNC_PAGES];
+       struct page *pbio_pages[RESYNC_PAGES], *sbio_pages[RESYNC_PAGES];
 
        /* Fix variable parts of all bios */
        vcnt = (r1_bio->sectors + PAGE_SIZE / 512 - 1) >> (PAGE_SHIFT - 9);
@@ -2017,7 +2020,6 @@ static void process_checks(struct r1bio *r1_bio)
                int j;
                int size;
                int error;
-               struct bio_vec *bi;
                struct bio *b = r1_bio->bios[i];
                if (b->bi_end_io != end_sync_read)
                        continue;
@@ -2051,6 +2053,11 @@ static void process_checks(struct r1bio *r1_bio)
                        break;
                }
        r1_bio->read_disk = primary;
+
+       /* .bi_vcnt has been set for all read bios */
+       bio_for_each_segment_all(bi, r1_bio->bios[primary], i)
+               pbio_pages[i] = bi->bv_page;
+
        for (i = 0; i < conf->raid_disks * 2; i++) {
                int j;
                struct bio *pbio = r1_bio->bios[primary];
@@ -2062,14 +2069,19 @@ static void process_checks(struct r1bio *r1_bio)
                /* Now we can 'fixup' the error value */
                sbio->bi_error = 0;
 
+               bio_for_each_segment_all(bi, sbio, j) {
+                       sbio_pages[j] = bi->bv_page;
+                       page_len[j] = bi->bv_len;
+               }
+
                if (!error) {
                        for (j = vcnt; j-- ; ) {
                                struct page *p, *s;
-                               p = pbio->bi_io_vec[j].bv_page;
-                               s = sbio->bi_io_vec[j].bv_page;
+                               p = pbio_pages[j];
+                               s = sbio_pages[j];
                                if (memcmp(page_address(p),
                                           page_address(s),
-                                          sbio->bi_io_vec[j].bv_len))
+                                          page_len[j]))
                                        break;
                        }
                } else
-- 
2.7.4

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