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>

4 files changed, 14 insertions, 5 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 2936ca4..20c49b1 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1533,8 +1533,6 @@ static int cleaner_kthread(void *arg)
 	struct btrfs_root *root = arg;
 
 	do {
-		vfs_check_frozen(root->fs_info->sb, SB_FREEZE_WRITE);
-
 		if (!(root->fs_info->sb->s_flags & MS_RDONLY) &&
 		    mutex_trylock(&root->fs_info->cleaner_mutex)) {
 			btrfs_run_delayed_iputs(root);
@@ -1566,7 +1564,6 @@ static int transaction_kthread(void *arg)
 	do {
 		cannot_commit = false;
 		delay = HZ * 30;
-		vfs_check_frozen(root->fs_info->sb, SB_FREEZE_WRITE);
 		mutex_lock(&root->fs_info->transaction_kthread_mutex);
 
 		spin_lock(&root->fs_info->trans_lock);
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 9aa01ec..5caf285 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;
 }
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index fb8d671..f4d9017 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -6620,6 +6620,7 @@ int btrfs_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 	u64 page_start;
 	u64 page_end;
 
+	sb_start_pagefault(inode->i_sb);
 	ret  = btrfs_delalloc_reserve_space(inode, PAGE_CACHE_SIZE);
 	if (!ret) {
 		ret = file_update_time(vma->vm_file);
@@ -6709,12 +6710,15 @@ again:
 	unlock_extent_cached(io_tree, page_start, page_end, &cached_state, GFP_NOFS);
 
 out_unlock:
-	if (!ret)
+	if (!ret) {
+		sb_end_pagefault(inode->i_sb);
 		return VM_FAULT_LOCKED;
+	}
 	unlock_page(page);
 out:
 	btrfs_delalloc_release_space(inode, PAGE_CACHE_SIZE);
 out_noreserve:
+	sb_end_pagefault(inode->i_sb);
 	return ret;
 }
 
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index b72b068..fa67ba5 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -329,6 +329,8 @@ again:
 	if (!h)
 		return ERR_PTR(-ENOMEM);
 
+	sb_start_intwrite(root->fs_info->sb);
+
 	if (may_wait_transaction(root, type))
 		wait_current_trans(root);
 
@@ -339,6 +341,7 @@ again:
 	} while (ret == -EBUSY);
 
 	if (ret < 0) {
+		sb_end_intwrite(root->fs_info->sb);
 		kmem_cache_free(btrfs_trans_handle_cachep, h);
 		return ERR_PTR(ret);
 	}
@@ -528,6 +531,8 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
 		count++;
 	}
 
+	sb_end_intwrite(root->fs_info->sb);
+
 	if (lock && !atomic_read(&root->fs_info->open_ioctl_trans) &&
 	    should_end_transaction(trans, root)) {
 		trans->transaction->blocked = 1;
@@ -1517,6 +1522,8 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 	put_transaction(cur_trans);
 	put_transaction(cur_trans);
 
+	sb_end_intwrite(root->fs_info->sb);
+
 	trace_btrfs_transaction_commit(root);
 
 	btrfs_scrub_continue(root);