[PATCH 16/17] md: raid10: avoid direct access to bvec table in reshape_request

[Ming Lei]

The cost is 128bytes(8*16) stack space in kernel thread context, and
just use the bio helper to retrieve pages from bio.

Signed-off-by: Ming Lei <tom.leim...@gmail.com>
---
 drivers/md/raid10.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index c7d2f73565d9..5016ce8163c3 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -4383,6 +4383,8 @@ static sector_t reshape_request(struct mddev *mddev, 
sector_t sector_nr,
        struct bio *blist;
        struct bio *bio, *read_bio;
        int sectors_done = 0;
+       struct bio_vec *bvl;
+       struct page *pages[RESYNC_PAGES];
 
        if (sector_nr == 0) {
                /* If restarting in the middle, skip the initial sectors */
@@ -4546,9 +4548,12 @@ static sector_t reshape_request(struct mddev *mddev, 
sector_t sector_nr,
 
        /* Now add as many pages as possible to all of these bios. */
 
+       bio_for_each_segment_all(bvl, r10_bio->devs[0].bio, s)
+               pages[s] = bvl->bv_page;
+
        nr_sectors = 0;
        for (s = 0 ; s < max_sectors; s += PAGE_SIZE >> 9) {
-               struct page *page = 
r10_bio->devs[0].bio->bi_io_vec[s/(PAGE_SIZE>>9)].bv_page;
+               struct page *page = pages[s / (PAGE_SIZE >> 9)];
                int len = (max_sectors - s) << 9;
                if (len > PAGE_SIZE)
                        len = PAGE_SIZE;
-- 
2.7.4