f2fs: support volatile operations for transient data

This patch adds support for volatile writes which keep data pages in memory
until f2fs_evict_inode is called by iput.

For instance, we can use this feature for the sqlite database as follows.
While supporting atomic writes for main database file, we can keep its journal
data temporarily in the page cache by the following sequence.

1. open
 -> ioctl(F2FS_IOC_START_VOLATILE_WRITE);
2. writes
 : keep all the data in the page cache.
3. flush to the database file with atomic writes
  a. ioctl(F2FS_IOC_START_ATOMIC_WRITE);
  b. writes
  c. ioctl(F2FS_IOC_COMMIT_ATOMIC_WRITE);
4. close
 -> drop the cached data

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

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
index 1b85f72..0deead4 100644
--- a/fs/f2fs/inode.c
+++ b/fs/f2fs/inode.c
@@ -270,7 +270,7 @@ void f2fs_evict_inode(struct inode *inode)
 	nid_t xnid = F2FS_I(inode)->i_xattr_nid;
 
 	/* some remained atomic pages should discarded */
-	if (f2fs_is_atomic_file(inode))
+	if (f2fs_is_atomic_file(inode) || f2fs_is_volatile_file(inode))
 		commit_inmem_pages(inode, true);
 
 	trace_f2fs_evict_inode(inode);