nilfs2: add read ahead mode to nilfs_btnode_submit_block

This adds mode argument to nilfs_btnode_submit_block() function and
allows it to issue a read-ahead request.

An optional submit_ptr argument is also added to store the actual
block address for which bio is sent.  submit_ptr is used for a series
of read-ahead requests, and helps to decide if each requested block is
continous to the previous one on disk.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

1 files changed, 14 insertions, 3 deletions

diff --git a/fs/nilfs2/btnode.c b/fs/nilfs2/btnode.c
index 0a6834bb278e..f78ab1044d1d 100644
--- a/fs/nilfs2/btnode.c
+++ b/fs/nilfs2/btnode.c
@@ -96,7 +96,8 @@ 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);
@@ -127,7 +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 */
@@ -138,8 +148,9 @@ 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;