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, 5 deletions

diff --git a/fs/open.c b/fs/open.c
index ebef0c5fa10c..dcefb2f02d10 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -670,6 +670,7 @@ static int do_dentry_open(struct file *f,
                         put_write_access(inode);
                         goto cleanup_file;
                 }
+                f->f_mode |= FMODE_WRITER;
         }
 
         f->f_mapping = inode->i_mapping;
@@ -715,11 +716,9 @@ static int do_dentry_open(struct file *f,
 
 cleanup_all:
         fops_put(f->f_op);
-        if (f->f_mode & FMODE_WRITE) {
-                if (!special_file(inode->i_mode)) {
-                        put_write_access(inode);
-                        __mnt_drop_write(f->f_path.mnt);
-                }
+        if (f->f_mode & FMODE_WRITER) {
+                put_write_access(inode);
+                __mnt_drop_write(f->f_path.mnt);
         }
 cleanup_file:
         path_put(&f->f_path);