From aceaf78da92a53f5e1b105649a1b8c0afdb2135c Mon Sep 17 00:00:00 2001
From: Dave Hansen <haveblue@us.ibm.com>
Date: Fri, 15 Feb 2008 14:37:31 -0800
Subject: [PATCH] [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>
---
fs/file_table.c | 21 +++++++++++++++++++--
fs/nfsd/nfs4state.c | 3 ++-
include/linux/file.h | 1 +
3 files changed, 22 insertions(+), 3 deletions(-)
diff --git a/fs/file_table.c b/fs/file_table.c
index 986ff4ed0a7cb..3f73eb1f195a1 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -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);
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index bcb97d8e8b8bd..81a75f3081f43 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -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;
}
}
diff --git a/include/linux/file.h b/include/linux/file.h
index 7239baac81a9e..653477021e4c5 100644
--- a/include/linux/file.h
+++ b/include/linux/file.h
@@ -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;
--
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