tree edb3b2894dfb09f42cb45b6ad0f3d40c84a4dd7b
parent 88b88a66797159949cec32eaab12b4968f6fae2d
author Jaegeuk Kim <jaegeuk@kernel.org> 1412637076 -0700
committer Jaegeuk Kim <jaegeuk@kernel.org> 1412708081 -0700

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>