f2fs: checkpoint disabling

Note that, it requires "f2fs: return correct errno in f2fs_gc".

This adds a lightweight non-persistent snapshotting scheme to f2fs.

To use, mount with the option checkpoint=disable, and to return to
normal operation, remount with checkpoint=enable. If the filesystem
is shut down before remounting with checkpoint=enable, it will revert
back to its apparent state when it was first mounted with
checkpoint=disable. This is useful for situations where you wish to be
able to roll back the state of the disk in case of some critical
failure.

Signed-off-by: Daniel Rosenberg <drosen@google.com>
[Jaegeuk Kim: use SB_RDONLY instead of MS_RDONLY]
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

1 files changed, 13 insertions, 1 deletions

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 873f9ea7769f..9ef6f1f01eda 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -537,7 +537,8 @@ skip:
 	if (fio->in_list)
 		goto next;
 out:
-	if (is_sbi_flag_set(sbi, SBI_IS_SHUTDOWN))
+	if (is_sbi_flag_set(sbi, SBI_IS_SHUTDOWN) ||
+				f2fs_is_checkpoint_ready(sbi))
 		__submit_merged_bio(io);
 	up_write(&io->io_rwsem);
 }
@@ -1703,6 +1704,10 @@ static inline bool check_inplace_update_policy(struct inode *inode,
 			is_inode_flag_set(inode, FI_NEED_IPU))
 		return true;
 
+	if (unlikely(fio && is_sbi_flag_set(sbi, SBI_CP_DISABLED) &&
+			!f2fs_is_checkpointed_data(sbi, fio->old_blkaddr)))
+		return true;
+
 	return false;
 }
 
@@ -1733,6 +1738,9 @@ bool f2fs_should_update_outplace(struct inode *inode, struct f2fs_io_info *fio)
 			return true;
 		if (IS_ATOMIC_WRITTEN_PAGE(fio->page))
 			return true;
+		if (unlikely(is_sbi_flag_set(sbi, SBI_CP_DISABLED) &&
+			f2fs_is_checkpointed_data(sbi, fio->old_blkaddr)))
+			return true;
 	}
 	return false;
 }
@@ -2353,6 +2361,10 @@ static int f2fs_write_begin(struct file *file, struct address_space *mapping,
 
 	trace_f2fs_write_begin(inode, pos, len, flags);
 
+	err = f2fs_is_checkpoint_ready(sbi);
+	if (err)
+		goto fail;
+
 	if ((f2fs_is_atomic_file(inode) &&
 			!f2fs_available_free_memory(sbi, INMEM_PAGES)) ||
 			is_inode_flag_set(inode, FI_ATOMIC_REVOKE_REQUEST)) {