pnfsblock: limit bio page count

One bio can have at most BIO_MAX_PAGES pages. We should limit it bec otherwise
bio_alloc will fail when there are many pages in one read/write_pagelist.

Cc: <stable@vger.kernel.org> #3.1+
Signed-off-by: Peng Tao <peng_tao@emc.com>
Signed-off-by: Benny Halevy <bhalevy@tonian.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 11 insertions, 6 deletions

diff --git a/fs/nfs/blocklayout/blocklayout.c b/fs/nfs/blocklayout/blocklayout.c
index 6d39e9ab1e6..baf0bf2acbd 100644
--- a/fs/nfs/blocklayout/blocklayout.c
+++ b/fs/nfs/blocklayout/blocklayout.c
@@ -146,14 +146,19 @@ static struct bio *bl_alloc_init_bio(int npg, sector_t isect,
 {
         struct bio *bio;
 
+        npg = min(npg, BIO_MAX_PAGES);
         bio = bio_alloc(GFP_NOIO, npg);
-        if (!bio)
-                return NULL;
+        if (!bio && (current->flags & PF_MEMALLOC)) {
+                while (!bio && (npg /= 2))
+                        bio = bio_alloc(GFP_NOIO, npg);
+        }
 
-        bio->bi_sector = isect - be->be_f_offset + be->be_v_offset;
-        bio->bi_bdev = be->be_mdev;
-        bio->bi_end_io = end_io;
-        bio->bi_private = par;
+        if (bio) {
+                bio->bi_sector = isect - be->be_f_offset + be->be_v_offset;
+                bio->bi_bdev = be->be_mdev;
+                bio->bi_end_io = end_io;
+                bio->bi_private = par;
+        }
         return bio;
 }