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>

7 files changed, 36 insertions, 10 deletions

diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index f54b83b4d90b..590ea50c80a7 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -549,6 +549,10 @@ static void block_operations(struct f2fs_sb_info *sbi)
                 .nr_to_write = LONG_MAX,
                 .for_reclaim = 0,
         };
+        struct blk_plug plug;
+
+        blk_start_plug(&plug);
+
 retry_flush_dents:
         mutex_lock_all(sbi);
 
@@ -571,6 +575,7 @@ retry_flush_nodes:
                 sync_node_pages(sbi, 0, &wbc);
                 goto retry_flush_nodes;
         }
+        blk_finish_plug(&plug);
 }
 
 static void unblock_operations(struct f2fs_sb_info *sbi)
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;
 }
diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
index cd3342d4a3a7..3ddb1bc7d07a 100644
--- a/fs/f2fs/dir.c
+++ b/fs/f2fs/dir.c
@@ -148,7 +148,7 @@ static struct f2fs_dir_entry *find_in_level(struct inode *dir,
 
         for (; bidx < end_block; bidx++) {
                 /* no need to allocate new dentry pages to all the indices */
-                dentry_page = find_data_page(dir, bidx);
+                dentry_page = find_data_page(dir, bidx, true);
                 if (IS_ERR(dentry_page)) {
                         room = true;
                         continue;
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 06cc75c66c88..6283c8d77c2e 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1023,7 +1023,7 @@ void destroy_checkpoint_caches(void);
  */
 int reserve_new_block(struct dnode_of_data *);
 void update_extent_cache(block_t, struct dnode_of_data *);
-struct page *find_data_page(struct inode *, pgoff_t);
+struct page *find_data_page(struct inode *, pgoff_t, bool);
 struct page *get_lock_data_page(struct inode *, pgoff_t);
 struct page *get_new_data_page(struct inode *, pgoff_t, bool);
 int f2fs_readpage(struct f2fs_sb_info *, struct page *, block_t, int);
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 0e56db2d3cc9..9dfcdab5ea7c 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -212,7 +212,7 @@ static void truncate_partial_data_page(struct inode *inode, u64 from)
         if (!offset)
                 return;
 
-        page = find_data_page(inode, from >> PAGE_CACHE_SHIFT);
+        page = find_data_page(inode, from >> PAGE_CACHE_SHIFT, false);
         if (IS_ERR(page))
                 return;
 
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 6ed3263eeee8..25a1f7e593e0 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -386,6 +386,7 @@ static void gc_node_segment(struct f2fs_sb_info *sbi,
 
 next_step:
         entry = sum;
+
         for (off = 0; off < sbi->blocks_per_seg; off++, entry++) {
                 nid_t nid = le32_to_cpu(entry->nid);
                 struct page *node_page;
@@ -417,6 +418,7 @@ next_step:
                 f2fs_put_page(node_page, 1);
                 stat_inc_node_blk_count(sbi, 1);
         }
+
         if (initial) {
                 initial = false;
                 goto next_step;
@@ -545,6 +547,7 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
 
 next_step:
         entry = sum;
+
         for (off = 0; off < sbi->blocks_per_seg; off++, entry++) {
                 struct page *data_page;
                 struct inode *inode;
@@ -582,7 +585,7 @@ next_step:
                                 continue;
 
                         data_page = find_data_page(inode,
-                                        start_bidx + ofs_in_node);
+                                        start_bidx + ofs_in_node, false);
                         if (IS_ERR(data_page))
                                 goto next_iput;
 
@@ -603,6 +606,7 @@ next_step:
 next_iput:
                 iput(inode);
         }
+
         if (++phase < 4)
                 goto next_step;
 
@@ -636,12 +640,15 @@ static void do_garbage_collect(struct f2fs_sb_info *sbi, unsigned int segno,
 {
         struct page *sum_page;
         struct f2fs_summary_block *sum;
+        struct blk_plug plug;
 
         /* read segment summary of victim */
         sum_page = get_sum_page(sbi, segno);
         if (IS_ERR(sum_page))
                 return;
 
+        blk_start_plug(&plug);
+
         sum = page_address(sum_page);
 
         switch (GET_SUM_TYPE((&sum->footer))) {
@@ -652,6 +659,8 @@ static void do_garbage_collect(struct f2fs_sb_info *sbi, unsigned int segno,
                 gc_data_segment(sbi, sum->entries, ilist, segno, gc_type);
                 break;
         }
+        blk_finish_plug(&plug);
+
         stat_inc_seg_count(sbi, GET_SUM_TYPE((&sum->footer)));
         stat_inc_call_count(sbi->stat_info);
 
diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index 5a825502b0b0..a0aa0446a237 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -89,10 +89,13 @@ static void ra_nat_pages(struct f2fs_sb_info *sbi, int nid)
 {
         struct address_space *mapping = sbi->meta_inode->i_mapping;
         struct f2fs_nm_info *nm_i = NM_I(sbi);
+        struct blk_plug plug;
         struct page *page;
         pgoff_t index;
         int i;
 
+        blk_start_plug(&plug);
+
         for (i = 0; i < FREE_NID_PAGES; i++, nid += NAT_ENTRY_PER_BLOCK) {
                 if (nid >= nm_i->max_nid)
                         nid = 0;
@@ -110,6 +113,7 @@ static void ra_nat_pages(struct f2fs_sb_info *sbi, int nid)
 
                 f2fs_put_page(page, 0);
         }
+        blk_finish_plug(&plug);
 }
 
 static struct nat_entry *__lookup_nat_cache(struct f2fs_nm_info *nm_i, nid_t n)
@@ -942,6 +946,7 @@ struct page *get_node_page_ra(struct page *parent, int start)
 {
         struct f2fs_sb_info *sbi = F2FS_SB(parent->mapping->host->i_sb);
         struct address_space *mapping = sbi->node_inode->i_mapping;
+        struct blk_plug plug;
         struct page *page;
         int err, i, end;
         nid_t nid;
@@ -961,6 +966,8 @@ struct page *get_node_page_ra(struct page *parent, int start)
         else if (err == LOCKED_PAGE)
                 goto page_hit;
 
+        blk_start_plug(&plug);
+
         /* Then, try readahead for siblings of the desired node */
         end = start + MAX_RA_NODE;
         end = min(end, NIDS_PER_BLOCK);
@@ -971,6 +978,8 @@ struct page *get_node_page_ra(struct page *parent, int start)
                 ra_node_page(sbi, nid);
         }
 
+        blk_finish_plug(&plug);
+
         lock_page(page);
 
 page_hit: