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>

4 files changed, 22 insertions, 8 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;
diff --git a/fs/nilfs2/btnode.h b/fs/nilfs2/btnode.h
index 07da83f07712..79037494f1e0 100644
--- a/fs/nilfs2/btnode.h
+++ b/fs/nilfs2/btnode.h
@@ -42,8 +42,8 @@ void nilfs_btnode_cache_init(struct address_space *, struct backing_dev_info *);
 void nilfs_btnode_cache_clear(struct address_space *);
 struct buffer_head *nilfs_btnode_create_block(struct address_space *btnc,
                                               __u64 blocknr);
-int nilfs_btnode_submit_block(struct address_space *, __u64, sector_t,
-                              struct buffer_head **);
+int nilfs_btnode_submit_block(struct address_space *, __u64, sector_t, int,
+                              struct buffer_head **, sector_t *);
 void nilfs_btnode_delete(struct buffer_head *);
 int nilfs_btnode_prepare_change_key(struct address_space *,
                                     struct nilfs_btnode_chkey_ctxt *);
diff --git a/fs/nilfs2/btree.c b/fs/nilfs2/btree.c
index 6462c7026479..4669389bf686 100644
--- a/fs/nilfs2/btree.c
+++ b/fs/nilfs2/btree.c
@@ -71,9 +71,10 @@ static int nilfs_btree_get_block(const struct nilfs_bmap *btree, __u64 ptr,
 {
         struct address_space *btnc = &NILFS_BMAP_I(btree)->i_btnode_cache;
         struct buffer_head *bh;
+        sector_t pbn = 0;
         int err;
 
-        err = nilfs_btnode_submit_block(btnc, ptr, 0, bhp);
+        err = nilfs_btnode_submit_block(btnc, ptr, pbn, READ, bhp, &pbn);
         if (err)
                 return err == -EEXIST ? 0 : err;
 
diff --git a/fs/nilfs2/gcinode.c b/fs/nilfs2/gcinode.c
index b6343825f91a..bed3a783129b 100644
--- a/fs/nilfs2/gcinode.c
+++ b/fs/nilfs2/gcinode.c
@@ -151,8 +151,10 @@ int nilfs_gccache_submit_read_data(struct inode *inode, sector_t blkoff,
 int nilfs_gccache_submit_read_node(struct inode *inode, sector_t pbn,
                                    __u64 vbn, struct buffer_head **out_bh)
 {
-        int ret = nilfs_btnode_submit_block(&NILFS_I(inode)->i_btnode_cache,
-                                            vbn ? : pbn, pbn, out_bh);
+        int ret;
+
+        ret = nilfs_btnode_submit_block(&NILFS_I(inode)->i_btnode_cache,
+                                        vbn ? : pbn, pbn, READ, out_bh, &pbn);
         if (ret == -EEXIST) /* internal code (cache hit) */
                 ret = 0;
         return ret;