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>

diff --git a/fs/nfs/blocklayout/blocklayout.c b/fs/nfs/blocklayout/blocklayout.c
index 6d39e9a..baf0bf2 100644 (file)
--- 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;
 }