f2fs: introduce nr_pages_to_write for segment alignment

This patch introduces nr_pages_to_write to align page writes to the segment
or other operational unit size, which can be tuned according to the system
environment.

Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

4 files changed, 36 insertions, 19 deletions

diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index aef32f36e2f3..2a00c94726fb 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -187,18 +187,19 @@ static int f2fs_write_meta_pages(struct address_space *mapping,
                                 struct writeback_control *wbc)
 {
         struct f2fs_sb_info *sbi = F2FS_SB(mapping->host->i_sb);
-        int nrpages = nr_pages_to_skip(sbi, META);
-        long written;
+        long diff, written;
 
         /* collect a number of dirty meta pages and write together */
-        if (wbc->for_kupdate || get_pages(sbi, F2FS_DIRTY_META) < nrpages)
+        if (wbc->for_kupdate ||
+                get_pages(sbi, F2FS_DIRTY_META) < nr_pages_to_skip(sbi, META))
                 goto skip_write;
 
         /* if mounting is failed, skip writing node pages */
         mutex_lock(&sbi->cp_mutex);
-        written = sync_meta_pages(sbi, META, nrpages);
+        diff = nr_pages_to_write(sbi, META, wbc);
+        written = sync_meta_pages(sbi, META, wbc->nr_to_write);
         mutex_unlock(&sbi->cp_mutex);
-        wbc->nr_to_write -= written;
+        wbc->nr_to_write = max((long)0, wbc->nr_to_write - written - diff);
         return 0;
 
 skip_write:
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 3bc380942068..b0c923aef229 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -844,8 +844,6 @@ redirty_out:
         return AOP_WRITEPAGE_ACTIVATE;
 }
 
-#define MAX_DESIRED_PAGES_WP    4096
-
 static int __f2fs_writepage(struct page *page, struct writeback_control *wbc,
                         void *data)
 {
@@ -862,7 +860,7 @@ static int f2fs_write_data_pages(struct address_space *mapping,
         struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
         bool locked = false;
         int ret;
-        long excess_nrtw = 0, desired_nrtw;
+        long diff;
 
         /* deal with chardevs and other special file */
         if (!mapping->a_ops->writepage)
@@ -872,11 +870,7 @@ static int f2fs_write_data_pages(struct address_space *mapping,
                         get_dirty_dents(inode) < nr_pages_to_skip(sbi, DATA))
                 goto skip_write;
 
-        if (wbc->nr_to_write < MAX_DESIRED_PAGES_WP) {
-                desired_nrtw = MAX_DESIRED_PAGES_WP;
-                excess_nrtw = desired_nrtw - wbc->nr_to_write;
-                wbc->nr_to_write = desired_nrtw;
-        }
+        diff = nr_pages_to_write(sbi, DATA, wbc);
 
         if (!S_ISDIR(inode->i_mode)) {
                 mutex_lock(&sbi->writepages);
@@ -890,7 +884,7 @@ static int f2fs_write_data_pages(struct address_space *mapping,
 
         remove_dirty_dir_inode(inode);
 
-        wbc->nr_to_write -= excess_nrtw;
+        wbc->nr_to_write = max((long)0, wbc->nr_to_write - diff);
         return ret;
 
 skip_write:
diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index 7cc146bcbfed..5e9c38e846a5 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -1202,7 +1202,7 @@ static int f2fs_write_node_pages(struct address_space *mapping,
                             struct writeback_control *wbc)
 {
         struct f2fs_sb_info *sbi = F2FS_SB(mapping->host->i_sb);
-        long nr_to_write = wbc->nr_to_write;
+        long diff;
 
         /* balancing f2fs's metadata in background */
         f2fs_balance_fs_bg(sbi);
@@ -1211,12 +1211,10 @@ static int f2fs_write_node_pages(struct address_space *mapping,
         if (get_pages(sbi, F2FS_DIRTY_NODES) < nr_pages_to_skip(sbi, NODE))
                 goto skip_write;
 
-        /* if mounting is failed, skip writing node pages */
-        wbc->nr_to_write = 3 * max_hw_blocks(sbi);
+        diff = nr_pages_to_write(sbi, NODE, wbc);
         wbc->sync_mode = WB_SYNC_NONE;
         sync_node_pages(sbi, 0, wbc);
-        wbc->nr_to_write = nr_to_write - (3 * max_hw_blocks(sbi) -
-                                                wbc->nr_to_write);
+        wbc->nr_to_write = max((long)0, wbc->nr_to_write - diff);
         return 0;
 
 skip_write:
diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
index bbd976100d14..9fc46ee27bb8 100644
--- a/fs/f2fs/segment.h
+++ b/fs/f2fs/segment.h
@@ -683,3 +683,27 @@ static inline int nr_pages_to_skip(struct f2fs_sb_info *sbi, int type)
         else
                 return 0;
 }
+
+/*
+ * When writing pages, it'd better align nr_to_write for segment size.
+ */
+static inline long nr_pages_to_write(struct f2fs_sb_info *sbi, int type,
+                                        struct writeback_control *wbc)
+{
+        long nr_to_write, desired;
+
+        if (wbc->sync_mode != WB_SYNC_NONE)
+                return 0;
+
+        nr_to_write = wbc->nr_to_write;
+
+        if (type == DATA)
+                desired = 4096;
+        else if (type == NODE)
+                desired = 3 * max_hw_blocks(sbi);
+        else
+                desired = MAX_BIO_BLOCKS(max_hw_blocks(sbi));
+
+        wbc->nr_to_write = desired;
+        return desired - nr_to_write;
+}