f2fs: give a chance to merge IOs by IO scheduler

Previously, background GC submits many 4KB read requests to load victim blocks
and/or its (i)node blocks.

...
f2fs_gc : f2fs_readpage: ino = 1, page_index = 0xb61, blkaddr = 0x3b964ed
f2fs_gc : block_rq_complete: 8,16 R () 499854968 + 8 [0]
f2fs_gc : f2fs_readpage: ino = 1, page_index = 0xb6f, blkaddr = 0x3b964ee
f2fs_gc : block_rq_complete: 8,16 R () 499854976 + 8 [0]
f2fs_gc : f2fs_readpage: ino = 1, page_index = 0xb79, blkaddr = 0x3b964ef
f2fs_gc : block_rq_complete: 8,16 R () 499854984 + 8 [0]
...

However, by the fact that many IOs are sequential, we can give a chance to merge
the IOs by IO scheduler.
In order to do that, let's use blk_plug.

...
f2fs_gc : f2fs_iget: ino = 143
f2fs_gc : f2fs_readpage: ino = 143, page_index = 0x1c6, blkaddr = 0x2e6ee
f2fs_gc : f2fs_iget: ino = 143
f2fs_gc : f2fs_readpage: ino = 143, page_index = 0x1c7, blkaddr = 0x2e6ef
<idle> : block_rq_complete: 8,16 R () 1519616 + 8 [0]
<idle> : block_rq_complete: 8,16 R () 1519848 + 8 [0]
<idle> : block_rq_complete: 8,16 R () 1520432 + 96 [0]
<idle> : block_rq_complete: 8,16 R () 1520536 + 104 [0]
<idle> : block_rq_complete: 8,16 R () 1521008 + 112 [0]
<idle> : block_rq_complete: 8,16 R () 1521440 + 152 [0]
<idle> : block_rq_complete: 8,16 R () 1521688 + 144 [0]
<idle> : block_rq_complete: 8,16 R () 1522128 + 192 [0]
<idle> : block_rq_complete: 8,16 R () 1523256 + 328 [0]
...

Note that this issue should be addressed in checkpoint, and some readahead
flows too.

Reviewed-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

1 files changed, 9 insertions, 6 deletions

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 1220b5c2ea21..eba7e84d1ffd 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -172,7 +172,7 @@ end_update:
         return;
 }
 
-struct page *find_data_page(struct inode *inode, pgoff_t index)
+struct page *find_data_page(struct inode *inode, pgoff_t index, bool sync)
 {
         struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
         struct address_space *mapping = inode->i_mapping;
@@ -207,11 +207,14 @@ struct page *find_data_page(struct inode *inode, pgoff_t index)
                 return page;
         }
 
-        err = f2fs_readpage(sbi, page, dn.data_blkaddr, READ_SYNC);
-        wait_on_page_locked(page);
-        if (!PageUptodate(page)) {
-                f2fs_put_page(page, 0);
-                return ERR_PTR(-EIO);
+        err = f2fs_readpage(sbi, page, dn.data_blkaddr,
+                                        sync ? READ_SYNC : READA);
+        if (sync) {
+                wait_on_page_locked(page);
+                if (!PageUptodate(page)) {
+                        f2fs_put_page(page, 0);
+                        return ERR_PTR(-EIO);
+                }
         }
         return page;
 }