Commit aceaf78d authored by Dave Hansen's avatar Dave Hansen Committed by Al Viro
Browse files

[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: default avatarDave 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: default avatarAl Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 8366025e

fs/file_table.c

+19 −2
Original line number Diff line number Diff line
@@ -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);

fs/nfsd/nfs4state.c

+2 −1
Original line number Diff line number Diff line
@@ -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;

	}

}

include/linux/file.h

+1 −0
Original line number Diff line number Diff line
@@ -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;