1 files changed, 18 insertions, 5 deletions

diff --git a/fs/nilfs2/btnode.c b/fs/nilfs2/btnode.c
index 447ce47a3306..f78ab1044d1d 100644
--- a/fs/nilfs2/btnode.c
+++ b/fs/nilfs2/btnode.c
@@ -96,10 +96,12 @@ nilfs_btnode_create_block(struct address_space *btnc, __u64 blocknr)
 }
 
 int nilfs_btnode_submit_block(struct address_space *btnc, __u64 blocknr,
-                              sector_t pblocknr, struct buffer_head **pbh)
+                              sector_t pblocknr, int mode,
+                              struct buffer_head **pbh, sector_t *submit_ptr)
 {
         struct buffer_head *bh;
         struct inode *inode = NILFS_BTNC_I(btnc);
+        struct page *page;
         int err;
 
         bh = nilfs_grab_buffer(inode, btnc, blocknr, 1 << BH_NILFS_Node);
@@ -107,6 +109,7 @@ int nilfs_btnode_submit_block(struct address_space *btnc, __u64 blocknr,
                 return -ENOMEM;
 
         err = -EEXIST; /* internal code */
+        page = bh->b_page;
 
         if (buffer_uptodate(bh) || buffer_dirty(bh))
                 goto found;
@@ -125,7 +128,16 @@ int nilfs_btnode_submit_block(struct address_space *btnc, __u64 blocknr,
                         }
                 }
         }
-        lock_buffer(bh);
+
+        if (mode == READA) {
+                if (pblocknr != *submit_ptr + 1 || !trylock_buffer(bh)) {
+                        err = -EBUSY; /* internal code */
+                        brelse(bh);
+                        goto out_locked;
+                }
+        } else { /* mode == READ */
+                lock_buffer(bh);
+        }
         if (buffer_uptodate(bh)) {
                 unlock_buffer(bh);
                 err = -EEXIST; /* internal code */
@@ -136,15 +148,16 @@ int nilfs_btnode_submit_block(struct address_space *btnc, __u64 blocknr,
         bh->b_blocknr = pblocknr; /* set block address for read */
         bh->b_end_io = end_buffer_read_sync;
         get_bh(bh);
-        submit_bh(READ, bh);
+        submit_bh(mode, bh);
         bh->b_blocknr = blocknr; /* set back to the given block address */
+        *submit_ptr = pblocknr;
         err = 0;
 found:
         *pbh = bh;
 
 out_locked:
-        unlock_page(bh->b_page);
-        page_cache_release(bh->b_page);
+        unlock_page(page);
+        page_cache_release(page);
         return err;
 }