[PATCH 3.14 023/140] dont bother with {get,put}_write_access() on non-regular files

Greg Kroah-Hartman
2014-05-29T05:40:43Z

From: Al Viro <viro@zeniv.linux.org.uk>

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>

---
fs/file_table.c | 4 ++--
fs/open.c | 26 +++++++-------------------
2 files changed, 9 insertions(+), 21 deletions(-)

--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -209,10 +209,10 @@ static void drop_file_write_access(struc
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);
--- a/fs/open.c
+++ b/fs/open.c
@@ -641,23 +641,12 @@ 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;
}

@@ -690,12 +679,11 @@ 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;
@@ -742,7 +730,6 @@ static int do_dentry_open(struct file *f
cleanup_all:
fops_put(f->f_op);
if (f->f_mode & FMODE_WRITE) {
- put_write_access(inode);
if (!special_file(inode->i_mode)) {
/*
* We don't consider this a real
@@ -750,6 +737,7 @@ 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);
}