mark struct file that had write access grabbed by open()

new flag in ->f_mode - FMODE_WRITER.  Set by do_dentry_open() in case
when it has grabbed write access, checked by __fput() to decide whether
it wants to drop the sucker.  Allows to stop bothering with mnt_clone_write()
in alloc_file(), along with fewer special_file() checks.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 4 insertions, 33 deletions

diff --git a/fs/file_table.c b/fs/file_table.c
index ee20658a0647..ce1504fec5a1 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -177,43 +177,12 @@ struct file *alloc_file(struct path *path, fmode_t mode,
         file->f_mapping = path->dentry->d_inode->i_mapping;
         file->f_mode = mode;
         file->f_op = fop;
-
-        /*
-         * These mounts don't really matter in practice
-         * for r/o bind mounts.  They aren't userspace-
-         * visible.  We do this for consistency, and so
-         * that we can do debugging checks at __fput()
-         */
-        if ((mode & FMODE_WRITE) && !special_file(path->dentry->d_inode->i_mode)) {
-                WARN_ON(mnt_clone_write(path->mnt));
-        }
         if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
                 i_readcount_inc(path->dentry->d_inode);
         return file;
 }
 EXPORT_SYMBOL(alloc_file);
 
-/**
- * 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.
- */
-static void drop_file_write_access(struct file *file)
-{
-        struct vfsmount *mnt = file->f_path.mnt;
-        struct dentry *dentry = file->f_path.dentry;
-        struct inode *inode = dentry->d_inode;
-
-        if (special_file(inode->i_mode))
-                return;
-
-        put_write_access(inode);
-        __mnt_drop_write(mnt);
-}
-
 /* the real guts of fput() - releasing the last reference to file
  */
 static void __fput(struct file *file)
@@ -248,8 +217,10 @@ static void __fput(struct file *file)
         put_pid(file->f_owner.pid);
         if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
                 i_readcount_dec(inode);
-        if (file->f_mode & FMODE_WRITE)
-                drop_file_write_access(file);
+        if (file->f_mode & FMODE_WRITER) {
+                put_write_access(inode);
+                __mnt_drop_write(mnt);
+        }
         file->f_path.dentry = NULL;
         file->f_path.mnt = NULL;
         file->f_inode = NULL;