[PATCH] r/o bind mounts: create helper to drop file write access
If someone decides to demote a file from r/w to just
r/o, they can use this same code as __fput().
NFS does just that, and will use this in the next
patch.
AV: drop write access in __fput() only after we evict from file list.
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Cc: Erez Zadok <ezk@cs.sunysb.edu>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: "J Bruce Fields" <bfields@fieldses.org>
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/file_table.c b/fs/file_table.c
index 986ff4e..3f73eb1 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -211,6 +211,23 @@
EXPORT_SYMBOL(fput);
+/**
+ * drop_file_write_access - give up ability to write to a file
+ * @file: the file to which we will stop writing
+ *
+ * This is a central place which will give up the ability
+ * to write to @file, along with access to write through
+ * its vfsmount.
+ */
+void drop_file_write_access(struct file *file)
+{
+ struct dentry *dentry = file->f_path.dentry;
+ struct inode *inode = dentry->d_inode;
+
+ put_write_access(inode);
+}
+EXPORT_SYMBOL_GPL(drop_file_write_access);
+
/* __fput is called from task context when aio completion releases the last
* last use of a struct file *. Do not use otherwise.
*/
@@ -236,10 +253,10 @@
if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL))
cdev_put(inode->i_cdev);
fops_put(file->f_op);
- if (file->f_mode & FMODE_WRITE)
- put_write_access(inode);
put_pid(file->f_owner.pid);
file_kill(file);
+ if (file->f_mode & FMODE_WRITE)
+ drop_file_write_access(file);
file->f_path.dentry = NULL;
file->f_path.mnt = NULL;
file_free(file);