md/raid1: store behind-write pages in bi_vecs.

When performing write-behind we allocate pages to store the data
during write.
Previously we just keep a list of pages.  Now we keep a list of
bi_vec which includes offset and size.
This means that the r1bio has complete information to create a new
bio which will be needed for retrying after write errors.

Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Namhyung Kim <namhyung@gmail.com>

1 files changed, 17 insertions, 16 deletions

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 141de75a6c7c..b16d2ee5e9dd 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -327,9 +327,9 @@ static void r1_bio_write_done(r1bio_t *r1_bio)
                         /* free extra copy of the data pages */
                         int i = r1_bio->behind_page_count;
                         while (i--)
-                                safe_put_page(r1_bio->behind_pages[i]);
-                        kfree(r1_bio->behind_pages);
-                        r1_bio->behind_pages = NULL;
+                                safe_put_page(r1_bio->behind_bvecs[i].bv_page);
+                        kfree(r1_bio->behind_bvecs);
+                        r1_bio->behind_bvecs = NULL;
                 }
                 /* clear the bitmap if all writes complete successfully */
                 bitmap_endwrite(r1_bio->mddev->bitmap, r1_bio->sector,
@@ -748,30 +748,31 @@ static void alloc_behind_pages(struct bio *bio, r1bio_t *r1_bio)
 {
         int i;
         struct bio_vec *bvec;
-        struct page **pages = kzalloc(bio->bi_vcnt * sizeof(struct page*),
+        struct bio_vec *bvecs = kzalloc(bio->bi_vcnt * sizeof(struct bio_vec),
                                         GFP_NOIO);
-        if (unlikely(!pages))
+        if (unlikely(!bvecs))
                 return;
 
         bio_for_each_segment(bvec, bio, i) {
-                pages[i] = alloc_page(GFP_NOIO);
-                if (unlikely(!pages[i]))
+                bvecs[i] = *bvec;
+                bvecs[i].bv_page = alloc_page(GFP_NOIO);
+                if (unlikely(!bvecs[i].bv_page))
                         goto do_sync_io;
-                memcpy(kmap(pages[i]) + bvec->bv_offset,
-                        kmap(bvec->bv_page) + bvec->bv_offset, bvec->bv_len);
-                kunmap(pages[i]);
+                memcpy(kmap(bvecs[i].bv_page) + bvec->bv_offset,
+                       kmap(bvec->bv_page) + bvec->bv_offset, bvec->bv_len);
+                kunmap(bvecs[i].bv_page);
                 kunmap(bvec->bv_page);
         }
-        r1_bio->behind_pages = pages;
+        r1_bio->behind_bvecs = bvecs;
         r1_bio->behind_page_count = bio->bi_vcnt;
         set_bit(R1BIO_BehindIO, &r1_bio->state);
         return;
 
 do_sync_io:
         for (i = 0; i < bio->bi_vcnt; i++)
-                if (pages[i])
-                        put_page(pages[i]);
-        kfree(pages);
+                if (bvecs[i].bv_page)
+                        put_page(bvecs[i].bv_page);
+        kfree(bvecs);
         PRINTK("%dB behind alloc failed, doing sync I/O\n", bio->bi_size);
 }
 
@@ -1058,7 +1059,7 @@ read_again:
                                                    &r1_bio->state));
                         first_clone = 0;
                 }
-                if (r1_bio->behind_pages) {
+                if (r1_bio->behind_bvecs) {
                         struct bio_vec *bvec;
                         int j;
 
@@ -1070,7 +1071,7 @@ read_again:
                          * them all
                          */
                         __bio_for_each_segment(bvec, mbio, j, 0)
-                                bvec->bv_page = r1_bio->behind_pages[j];
+                                bvec->bv_page = r1_bio->behind_bvecs[j].bv_page;
                         if (test_bit(WriteMostly, &conf->mirrors[i].rdev->flags))
                                 atomic_inc(&r1_bio->behind_remaining);
                 }