f2fs: add un/freeze_fs into super_operations

This patch supports ioctl FIFREEZE and FITHAW to snapshot filesystem.
Before calling f2fs_freeze, all writers would be suspended and sync_fs
would be completed. So no f2fs has to do something.
Just background gc operation should be skipped due to generate dirty
nodes and data until unfreeze.

Signed-off-by: Changman Lee <cm224.lee@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

3 files changed, 25 insertions, 0 deletions

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index c386910dacc5..9b5d0aad5daf 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -44,6 +44,11 @@ static int gc_thread_func(void *data)
                 if (kthread_should_stop())
                         break;
 
+                if (sbi->sb->s_writers.frozen >= SB_FREEZE_WRITE) {
+                        wait_ms = GC_THREAD_MAX_SLEEP_TIME;
+                        continue;
+                }
+
                 f2fs_balance_fs(sbi);
 
                 if (!test_opt(sbi, BG_GC))
diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
index 340a21be5a76..62433c63e2db 100644
--- a/fs/f2fs/inode.c
+++ b/fs/f2fs/inode.c
@@ -278,6 +278,7 @@ void f2fs_evict_inode(struct inode *inode)
         if (inode->i_nlink || is_bad_inode(inode))
                 goto no_delete;
 
+        sb_start_intwrite(inode->i_sb);
         set_inode_flag(F2FS_I(inode), FI_NO_ALLOC);
         i_size_write(inode, 0);
 
@@ -285,6 +286,7 @@ void f2fs_evict_inode(struct inode *inode)
                 f2fs_truncate(inode);
 
         remove_inode_page(inode);
+        sb_end_intwrite(inode->i_sb);
 no_delete:
         clear_inode(inode);
 }
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 25656b6869a4..0b18aee2ed25 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -143,6 +143,22 @@ int f2fs_sync_fs(struct super_block *sb, int sync)
         return 0;
 }
 
+static int f2fs_freeze(struct super_block *sb)
+{
+        int err;
+
+        if (sb->s_flags & MS_RDONLY)
+                return 0;
+
+        err = f2fs_sync_fs(sb, 1);
+        return err;
+}
+
+static int f2fs_unfreeze(struct super_block *sb)
+{
+        return 0;
+}
+
 static int f2fs_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
         struct super_block *sb = dentry->d_sb;
@@ -213,6 +229,8 @@ static struct super_operations f2fs_sops = {
         .evict_inode    = f2fs_evict_inode,
         .put_super      = f2fs_put_super,
         .sync_fs        = f2fs_sync_fs,
+        .freeze_fs      = f2fs_freeze,
+        .unfreeze_fs    = f2fs_unfreeze,
         .statfs         = f2fs_statfs,
 };