linux-kernel - [PATCH v10 2/5] Add optional __get xattr method paired to __vfs

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Message-Id: <20190724195719.218307-3-salyzyn@android.com>
Date:   Wed, 24 Jul 2019 12:57:13 -0700
From:   Mark Salyzyn <salyzyn@...roid.com>
To:     linux-kernel@...r.kernel.org
Cc:     kernel-team@...roid.com, Mark Salyzyn <salyzyn@...roid.com>,
        Miklos Szeredi <miklos@...redi.hu>,
        Jonathan Corbet <corbet@....net>,
        Vivek Goyal <vgoyal@...hat.com>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Amir Goldstein <amir73il@...il.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        linux-unionfs@...r.kernel.org, linux-doc@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Mark Salyzyn <salyzyn@...gle.com>,
        linux-fsdevel@...r.kernel.org
Subject: [PATCH v10 2/5] Add optional __get xattr method paired to __vfs_getxattr

Add an optional __get xattr method that would be called, if set, only
in __vfs_getxattr instead of the regular get xattr method.

Signed-off-by: Mark Salyzyn <salyzyn@...roid.com>
Cc: Miklos Szeredi <miklos@...redi.hu>
Cc: Jonathan Corbet <corbet@....net>
Cc: Vivek Goyal <vgoyal@...hat.com>
Cc: Eric W. Biederman <ebiederm@...ssion.com>
Cc: Amir Goldstein <amir73il@...il.com>
Cc: Randy Dunlap <rdunlap@...radead.org>
Cc: Stephen Smalley <sds@...ho.nsa.gov>
Cc: linux-unionfs@...r.kernel.org
Cc: linux-doc@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Cc: kernel-team@...roid.com
---
v10 - added to patch series
---
 fs/xattr.c            | 11 ++++++++++-
 include/linux/xattr.h |  7 +++++--
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/fs/xattr.c b/fs/xattr.c
index 90dd78f0eb27..b8f4734e222f 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -306,6 +306,9 @@ __vfs_getxattr(struct dentry *dentry, struct inode *inode, const char *name,
 	handler = xattr_resolve_name(inode, &name);
 	if (IS_ERR(handler))
 		return PTR_ERR(handler);
+	if (unlikely(handler->__get))
+		return handler->__get(handler, dentry, inode, name, value,
+				      size);
 	if (!handler->get)
 		return -EOPNOTSUPP;
 	return handler->get(handler, dentry, inode, name, value, size);
@@ -317,6 +320,7 @@ vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
 {
 	struct inode *inode = dentry->d_inode;
 	int error;
+	const struct xattr_handler *handler;
 
 	error = xattr_permission(inode, name, MAY_READ);
 	if (error)
@@ -339,7 +343,12 @@ vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
 		return ret;
 	}
 nolsm:
-	return __vfs_getxattr(dentry, inode, name, value, size);
+	handler = xattr_resolve_name(inode, &name);
+	if (IS_ERR(handler))
+		return PTR_ERR(handler);
+	if (!handler->get)
+		return -EOPNOTSUPP;
+	return handler->get(handler, dentry, inode, name, value, size);
 }
 EXPORT_SYMBOL_GPL(vfs_getxattr);
 
diff --git a/include/linux/xattr.h b/include/linux/xattr.h
index 6dad031be3c2..30f25e1ac571 100644
--- a/include/linux/xattr.h
+++ b/include/linux/xattr.h
@@ -30,10 +30,13 @@ struct xattr_handler {
 	const char *prefix;
 	int flags;      /* fs private flags */
 	bool (*list)(struct dentry *dentry);
-	int (*get)(const struct xattr_handler *, struct dentry *dentry,
+	int (*get)(const struct xattr_handler *handler, struct dentry *dentry,
 		   struct inode *inode, const char *name, void *buffer,
 		   size_t size);
-	int (*set)(const struct xattr_handler *, struct dentry *dentry,
+	int (*__get)(const struct xattr_handler *handler, struct dentry *dentry,
+		     struct inode *inode, const char *name, void *buffer,
+		     size_t size);
+	int (*set)(const struct xattr_handler *handler, struct dentry *dentry,
 		   struct inode *inode, const char *name, const void *buffer,
 		   size_t size, int flags);
 };
-- 
2.22.0.657.g960e92d24f-goog