f2fs: decrease the lock granularity during write_begin

This patch reduces the lock granularity during write_begin.
When the system is under memory pressure, it would be better to reduce
the locking time for the data pages.

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

1 files changed, 13 insertions, 1 deletions

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 91ff104b3849..a7bb98f5831a 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -909,6 +909,10 @@ repeat:
         page = grab_cache_page_write_begin(mapping, index, flags);
         if (!page)
                 return -ENOMEM;
+
+        /* to avoid latency during memory pressure */
+        unlock_page(page);
+
         *pagep = page;
 
         if (f2fs_has_inline_data(inode) && (pos + len) <= MAX_INLINE_DATA)
@@ -920,10 +924,18 @@ repeat:
         f2fs_unlock_op(sbi);
 
         if (err) {
-                f2fs_put_page(page, 1);
+                f2fs_put_page(page, 0);
                 return err;
         }
 inline_data:
+        lock_page(page);
+        if (unlikely(page->mapping != mapping)) {
+                f2fs_put_page(page, 1);
+                goto repeat;
+        }
+
+        f2fs_wait_on_page_writeback(page, DATA);
+
         if ((len == PAGE_CACHE_SIZE) || PageUptodate(page))
                 return 0;