f2fs: avoid f2fs_lock_op in f2fs_write_begin

If f2fs_write_begin is to update data, we can bypass calling f2fs_lock_op() in
order to avoid the checkpoint latency in the write syscall.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index d4839fc2b4ca341a220851dc9b0517da04023da2..f2a023edfc1d2219aef5fef71fefffe64d1f5794 100644 (file)
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1418,10 +1418,16 @@ static int prepare_write_begin(struct f2fs_sb_info *sbi,
        pgoff_t index = page->index;
        struct dnode_of_data dn;
        struct page *ipage;
+       bool locked = false;
+       struct extent_info ei;
        int err = 0;
 
-       f2fs_lock_op(sbi);
-
+       if (f2fs_has_inline_data(inode) ||
+                       (pos & PAGE_CACHE_MASK) >= i_size_read(inode)) {
+               f2fs_lock_op(sbi);
+               locked = true;
+       }
+restart:
        /* check inline_data */
        ipage = get_node_page(sbi, inode->i_ino);
        if (IS_ERR(ipage)) {
@@ -1436,22 +1442,42 @@ static int prepare_write_begin(struct f2fs_sb_info *sbi,
                        read_inline_data(page, ipage);
                        set_inode_flag(F2FS_I(inode), FI_DATA_EXIST);
                        sync_inode_page(&dn);
-                       goto done;
                } else {
                        err = f2fs_convert_inline_page(&dn, page);
                        if (err)
-                               goto err_out;
+                               goto out;
+                       if (dn.data_blkaddr == NULL_ADDR)
+                               err = f2fs_get_block(&dn, index);
+               }
+       } else if (locked) {
+               err = f2fs_get_block(&dn, index);
+       } else {
+               if (f2fs_lookup_extent_cache(inode, index, &ei)) {
+                       dn.data_blkaddr = ei.blk + index - ei.fofs;
+               } else {
+                       bool restart = false;
+
+                       /* hole case */
+                       err = get_dnode_of_data(&dn, index, LOOKUP_NODE);
+                       if (err || (!err && dn.data_blkaddr == NULL_ADDR))
+                               restart = true;
+                       if (restart) {
+                               f2fs_put_dnode(&dn);
+                               f2fs_lock_op(sbi);
+                               locked = true;
+                               goto restart;
+                       }
                }
        }
-       err = f2fs_get_block(&dn, index);
-done:
+
        /* convert_inline_page can make node_changed */
        *blk_addr = dn.data_blkaddr;
        *node_changed = dn.node_changed;
-err_out:
+out:
        f2fs_put_dnode(&dn);
 unlock_out:
-       f2fs_unlock_op(sbi);
+       if (locked)
+               f2fs_unlock_op(sbi);
        return err;
 }