[PATCH 04/19] btrfs: Push mnt_want_write() outside of i_mutex

[Jan Kara]

When mnt_want_write() starts to handle freezing it will get a full lock
semantics requiring proper lock ordering. So push mnt_want_write() call
consistently outside of i_mutex.

CC: Chris Mason <chris.ma...@oracle.com>
CC: linux-btrfs@vger.kernel.org
Signed-off-by: Jan Kara <j...@suse.cz>
---
 fs/btrfs/ioctl.c |   23 +++++++++++------------
 1 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 03bb62a..c855e55 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -192,6 +192,10 @@ static int btrfs_ioctl_setflags(struct file *file, void 
__user *arg)
        if (!inode_owner_or_capable(inode))
                return -EACCES;
 
+       ret = mnt_want_write_file(file);
+       if (ret)
+               return ret;
+
        mutex_lock(&inode->i_mutex);
 
        ip_oldflags = ip->flags;
@@ -206,10 +210,6 @@ static int btrfs_ioctl_setflags(struct file *file, void 
__user *arg)
                }
        }
 
-       ret = mnt_want_write_file(file);
-       if (ret)
-               goto out_unlock;
-
        if (flags & FS_SYNC_FL)
                ip->flags |= BTRFS_INODE_SYNC;
        else
@@ -271,9 +271,9 @@ static int btrfs_ioctl_setflags(struct file *file, void 
__user *arg)
                inode->i_flags = i_oldflags;
        }
 
-       mnt_drop_write_file(file);
  out_unlock:
        mutex_unlock(&inode->i_mutex);
+       mnt_drop_write_file(file);
        return ret;
 }
 
@@ -624,6 +624,10 @@ static noinline int btrfs_mksubvol(struct path *parent,
        struct dentry *dentry;
        int error;
 
+       error = mnt_want_write(parent->mnt);
+       if (error)
+               return error;
+
        mutex_lock_nested(&dir->i_mutex, I_MUTEX_PARENT);
 
        dentry = lookup_one_len(name, parent->dentry, namelen);
@@ -635,13 +639,9 @@ static noinline int btrfs_mksubvol(struct path *parent,
        if (dentry->d_inode)
                goto out_dput;
 
-       error = mnt_want_write(parent->mnt);
-       if (error)
-               goto out_dput;
-
        error = btrfs_may_create(dir, dentry);
        if (error)
-               goto out_drop_write;
+               goto out_dput;
 
        down_read(&BTRFS_I(dir)->root->fs_info->subvol_sem);
 
@@ -659,12 +659,11 @@ static noinline int btrfs_mksubvol(struct path *parent,
                fsnotify_mkdir(dir, dentry);
 out_up_read:
        up_read(&BTRFS_I(dir)->root->fs_info->subvol_sem);
-out_drop_write:
-       mnt_drop_write(parent->mnt);
 out_dput:
        dput(dentry);
 out_unlock:
        mutex_unlock(&dir->i_mutex);
+       mnt_drop_write(parent->mnt);
        return error;
 }
 
-- 
1.7.1

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