btrfs: Convert to new freezing mechanism

We convert btrfs_file_aio_write() to use new freeze check.  We also add proper
freeze protection to btrfs_page_mkwrite(). We also add freeze protection to
the transaction mechanism to avoid starting transactions on frozen filesystem.
At minimum this is necessary to stop iput() of unlinked file to change frozen
filesystem during truncation.

Checks in cleaner_kthread() and transaction_kthread() can be safely removed
since btrfs_freeze() will lock the mutexes and thus block the threads (and they
shouldn't have anything to do anyway).

CC: linux-btrfs@vger.kernel.org
CC: Chris Mason <chris.mason@oracle.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 9aa01ec2138d..5caf285c6e4d 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1379,7 +1379,7 @@ static ssize_t btrfs_file_aio_write(struct kiocb *iocb,
         ssize_t err = 0;
         size_t count, ocount;
 
-        vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
+        sb_start_write(inode->i_sb);
 
         mutex_lock(&inode->i_mutex);
 
@@ -1469,6 +1469,7 @@ static ssize_t btrfs_file_aio_write(struct kiocb *iocb,
                         num_written = err;
         }
 out:
+        sb_end_write(inode->i_sb);
         current->backing_dev_info = NULL;
         return num_written ? num_written : err;
 }