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 ebef0c5..dcefb2f 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);