don't bother with {get,put}_write_access() on non-regular files

commit dd20908a8a06b22c171f6c3fcdbdbd65bed07505 upstream.

it's pointless and actually leads to wrong behaviour in at least one
moderately convoluted case (pipe(), close one end, try to get to
another via /proc/*/fd and run into ETXTBUSY).

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/file_table.c b/fs/file_table.c
index 485dc0e..54a34be 100644 (file)
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -211,10 +211,10 @@ static 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);
-
        if (special_file(inode->i_mode))
                return;
+
+       put_write_access(inode);
        if (file_check_writeable(file) != 0)
                return;
        __mnt_drop_write(mnt);

diff --git a/fs/open.c b/fs/open.c
index 8c74100..86092bd 100644 (file)
--- a/fs/open.c
+++ b/fs/open.c
@@ -628,23 +628,12 @@ out:
 static inline int __get_file_write_access(struct inode *inode,
                                          struct vfsmount *mnt)
 {
-       int error;
-       error = get_write_access(inode);
+       int error = get_write_access(inode);
        if (error)
                return error;
-       /*
-        * Do not take mount writer counts on
-        * special files since no writes to
-        * the mount itself will occur.
-        */
-       if (!special_file(inode->i_mode)) {
-               /*
-                * Balanced in __fput()
-                */
-               error = __mnt_want_write(mnt);
-               if (error)
-                       put_write_access(inode);
-       }
+       error = __mnt_want_write(mnt);
+       if (error)
+               put_write_access(inode);
        return error;
 }
 
@@ -677,12 +666,11 @@ static int do_dentry_open(struct file *f,
 
        path_get(&f->f_path);
        inode = f->f_inode = f->f_path.dentry->d_inode;
-       if (f->f_mode & FMODE_WRITE) {
+       if (f->f_mode & FMODE_WRITE && !special_file(inode->i_mode)) {
                error = __get_file_write_access(inode, f->f_path.mnt);
                if (error)
                        goto cleanup_file;
-               if (!special_file(inode->i_mode))
-                       file_take_write(f);
+               file_take_write(f);
        }
 
        f->f_mapping = inode->i_mapping;
@@ -723,7 +711,6 @@ cleanup_all:
        fops_put(f->f_op);
        file_sb_list_del(f);
        if (f->f_mode & FMODE_WRITE) {
-               put_write_access(inode);
                if (!special_file(inode->i_mode)) {
                        /*
                         * We don't consider this a real
@@ -731,6 +718,7 @@ cleanup_all:
                         * because it all happenend right
                         * here, so just reset the state.
                         */
+                       put_write_access(inode);
                        file_reset_write(f);
                        __mnt_drop_write(f->f_path.mnt);
                }