[Devel] [PATCH 07/25] elevate writer count for chown and friends

[Dave Hansen]

chown/chmod,etc... don't call permission in the same way
that the normal "open for write" calls do.  They still
write to the filesystem, so bump the write count during
these operations.

Signed-off-by: Dave Hansen <haveblue at us.ibm.com>
---

 lxc-dave/fs/open.c |   37 +++++++++++++++++++++++++++++++++----
 1 file changed, 33 insertions(+), 4 deletions(-)

diff -puN fs/open.c~06-24-elevate-writer-count-for-chown-and-friends fs/open.c
--- lxc/fs/open.c~06-24-elevate-writer-count-for-chown-and-friends	2006-12-11 14:22:01.000000000 -0800
+++ lxc-dave/fs/open.c	2006-12-11 14:22:01.000000000 -0800
@@ -511,9 +511,12 @@ asmlinkage long sys_fchmod(unsigned int 
 	err = -EROFS;
 	if (IS_RDONLY(inode))
 		goto out_putf;
+	err = mnt_want_write(file->f_vfsmnt);
+	if (err)
+		goto out_putf;
 	err = -EPERM;
 	if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
-		goto out_putf;
+		goto out_drop_write;
 	mutex_lock(&inode->i_mutex);
 	if (mode == (mode_t) -1)
 		mode = inode->i_mode;
@@ -522,6 +525,8 @@ asmlinkage long sys_fchmod(unsigned int 
 	err = notify_change(dentry, &newattrs);
 	mutex_unlock(&inode->i_mutex);
 
+out_drop_write:
+	mnt_drop_write(file->f_vfsmnt);
 out_putf:
 	fput(file);
 out:
@@ -541,13 +546,16 @@ asmlinkage long sys_fchmodat(int dfd, co
 		goto out;
 	inode = nd.dentry->d_inode;
 
+	error = mnt_want_write(nd.mnt);
+	if (error)
+		goto dput_and_out;
 	error = -EROFS;
 	if (IS_RDONLY(inode))
-		goto dput_and_out;
+		goto out_drop_write;
 
 	error = -EPERM;
 	if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
-		goto dput_and_out;
+		goto out_drop_write;
 
 	mutex_lock(&inode->i_mutex);
 	if (mode == (mode_t) -1)
@@ -557,6 +565,8 @@ asmlinkage long sys_fchmodat(int dfd, co
 	error = notify_change(nd.dentry, &newattrs);
 	mutex_unlock(&inode->i_mutex);
 
+out_drop_write:
+	mnt_drop_write(nd.mnt);
 dput_and_out:
 	path_release(&nd);
 out:
@@ -582,7 +592,7 @@ static int chown_common(struct dentry * 
 	error = -EROFS;
 	if (IS_RDONLY(inode))
 		goto out;
-	error = -EPERM;
+ 	error = -EPERM;
 	if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
 		goto out;
 	newattrs.ia_valid =  ATTR_CTIME;
@@ -611,7 +621,12 @@ asmlinkage long sys_chown(const char __u
 	error = user_path_walk(filename, &nd);
 	if (error)
 		goto out;
+	error = mnt_want_write(nd.mnt);
+	if (error)
+		goto out_release;
 	error = chown_common(nd.dentry, user, group);
+	mnt_drop_write(nd.mnt);
+out_release:
 	path_release(&nd);
 out:
 	return error;
@@ -631,7 +646,12 @@ asmlinkage long sys_fchownat(int dfd, co
 	error = __user_walk_fd(dfd, filename, follow, &nd);
 	if (error)
 		goto out;
+	error = mnt_want_write(nd.mnt);
+	if (error)
+		goto out_release;
 	error = chown_common(nd.dentry, user, group);
+	mnt_drop_write(nd.mnt);
+out_release:
 	path_release(&nd);
 out:
 	return error;
@@ -645,7 +665,11 @@ asmlinkage long sys_lchown(const char __
 	error = user_path_walk_link(filename, &nd);
 	if (error)
 		goto out;
+	error = mnt_want_write(nd.mnt);
+	if (error)
+		goto out_release;
 	error = chown_common(nd.dentry, user, group);
+out_release:
 	path_release(&nd);
 out:
 	return error;
@@ -662,9 +686,14 @@ asmlinkage long sys_fchown(unsigned int 
 	if (!file)
 		goto out;
 
+	error = mnt_want_write(file->f_vfsmnt);
+	if (error)
+		goto out_fput;
 	dentry = file->f_path.dentry;
 	audit_inode(NULL, dentry->d_inode);
 	error = chown_common(dentry, user, group);
+	mnt_drop_write(file->f_vfsmnt);
+out_fput:
 	fput(file);
 out:
 	return error;
_
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