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[PATCH] r/o bind mounts: create helper to drop file write access 

If someone decides to demote a file from r/w to just
r/o, they can use this same code as __fput().

NFS does just that, and will use this in the next
patch.

AV: drop write access in __fput() only after we evict from file list.

Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Cc: Erez Zadok <ezk@cs.sunysb.edu>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: "J Bruce Fields" <bfields@fieldses.org>
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Dave Hansen 2008-02-15 14:37:31 -08:00 committed by Al Viro
parent 8366025eb8
commit aceaf78da9
3 changed files with 22 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
fs/file_table.c
View File

@ -211,6 +211,23 @@ void fput(struct file *file)
EXPORT_SYMBOL(fput);
/**
* 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.
*/
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);
}
EXPORT_SYMBOL_GPL(drop_file_write_access);
/* __fput is called from task context when aio completion releases the last
* last use of a struct file *. Do not use otherwise.
*/
@ -236,10 +253,10 @@ void __fput(struct file *file)
if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL))
cdev_put(inode->i_cdev);
fops_put(file->f_op);
if (file->f_mode & FMODE_WRITE)
put_write_access(inode);
put_pid(file->f_owner.pid);
file_kill(file);
if (file->f_mode & FMODE_WRITE)
drop_file_write_access(file);
file->f_path.dentry = NULL;
file->f_path.mnt = NULL;
file_free(file);

3
fs/nfsd/nfs4state.c
View File

@ -41,6 +41,7 @@
#include <linux/sunrpc/svc.h>
#include <linux/nfsd/nfsd.h>
#include <linux/nfsd/cache.h>
#include <linux/file.h>
#include <linux/mount.h>
#include <linux/workqueue.h>
#include <linux/smp_lock.h>
@ -1239,7 +1240,7 @@ static inline void
nfs4_file_downgrade(struct file *filp, unsigned int share_access)
{
if (share_access & NFS4_SHARE_ACCESS_WRITE) {
put_write_access(filp->f_path.dentry->d_inode);
drop_file_write_access(filp);
filp->f_mode = (filp->f_mode | FMODE_READ) & ~FMODE_WRITE;
}
}

1
include/linux/file.h
View File

@ -61,6 +61,7 @@ extern struct kmem_cache *filp_cachep;
extern void __fput(struct file *);
extern void fput(struct file *);
extern void drop_file_write_access(struct file *file);
struct file_operations;
struct vfsmount;