ceph: add acl for cephfs

Signed-off-by: Guangliang Zhao <lucienchao@gmail.com>
Reviewed-by: Li Wang <li.wang@ubuntykylin.com>
Reviewed-by: Zheng Yan <zheng.z.yan@intel.com>

9 files changed, 451 insertions, 13 deletions

diff --git a/fs/ceph/Kconfig b/fs/ceph/Kconfig
index ac9a2ef5bb9b..264e9bf83ff3 100644
--- a/fs/ceph/Kconfig
+++ b/fs/ceph/Kconfig
@@ -25,3 +25,16 @@ config CEPH_FSCACHE
           caching support for Ceph clients using FS-Cache
 
 endif
+
+config CEPH_FS_POSIX_ACL
+        bool "Ceph POSIX Access Control Lists"
+        depends on CEPH_FS
+        select FS_POSIX_ACL
+        help
+          POSIX Access Control Lists (ACLs) support permissions for users and
+          groups beyond the owner/group/world scheme.
+
+          To learn more about Access Control Lists, visit the POSIX ACLs for
+          Linux website <http://acl.bestbits.at/>.
+
+          If you don't know what Access Control Lists are, say N
diff --git a/fs/ceph/Makefile b/fs/ceph/Makefile
index 32e30106a2f0..85a4230b9bff 100644
--- a/fs/ceph/Makefile
+++ b/fs/ceph/Makefile
@@ -10,3 +10,4 @@ ceph-y := super.o inode.o dir.o file.o locks.o addr.o ioctl.o \
         debugfs.o
 
 ceph-$(CONFIG_CEPH_FSCACHE) += cache.o
+ceph-$(CONFIG_CEPH_FS_POSIX_ACL) += acl.o
diff --git a/fs/ceph/acl.c b/fs/ceph/acl.c
new file mode 100644
index 000000000000..64fddbc1d17b
--- /dev/null
+++ b/fs/ceph/acl.c
@@ -0,0 +1,332 @@
+/*
+ * linux/fs/ceph/acl.c
+ *
+ * Copyright (C) 2013 Guangliang Zhao, <lucienchao@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#include <linux/ceph/ceph_debug.h>
+#include <linux/fs.h>
+#include <linux/string.h>
+#include <linux/xattr.h>
+#include <linux/posix_acl_xattr.h>
+#include <linux/posix_acl.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+
+#include "super.h"
+
+static inline void ceph_set_cached_acl(struct inode *inode,
+                                        int type, struct posix_acl *acl)
+{
+        struct ceph_inode_info *ci = ceph_inode(inode);
+
+        spin_lock(&ci->i_ceph_lock);
+        if (__ceph_caps_issued_mask(ci, CEPH_CAP_XATTR_SHARED, 0))
+                set_cached_acl(inode, type, acl);
+        spin_unlock(&ci->i_ceph_lock);
+}
+
+static inline struct posix_acl *ceph_get_cached_acl(struct inode *inode,
+                                                        int type)
+{
+        struct ceph_inode_info *ci = ceph_inode(inode);
+        struct posix_acl *acl = ACL_NOT_CACHED;
+
+        spin_lock(&ci->i_ceph_lock);
+        if (__ceph_caps_issued_mask(ci, CEPH_CAP_XATTR_SHARED, 0))
+                acl = get_cached_acl(inode, type);
+        spin_unlock(&ci->i_ceph_lock);
+
+        return acl;
+}
+
+void ceph_forget_all_cached_acls(struct inode *inode)
+{
+        forget_all_cached_acls(inode);
+}
+
+struct posix_acl *ceph_get_acl(struct inode *inode, int type)
+{
+        int size;
+        const char *name;
+        char *value = NULL;
+        struct posix_acl *acl;
+
+        if (!IS_POSIXACL(inode))
+                return NULL;
+
+        acl = ceph_get_cached_acl(inode, type);
+        if (acl != ACL_NOT_CACHED)
+                return acl;
+
+        switch (type) {
+        case ACL_TYPE_ACCESS:
+                name = POSIX_ACL_XATTR_ACCESS;
+                break;
+        case ACL_TYPE_DEFAULT:
+                name = POSIX_ACL_XATTR_DEFAULT;
+                break;
+        default:
+                BUG();
+        }
+
+        size = __ceph_getxattr(inode, name, "", 0);
+        if (size > 0) {
+                value = kzalloc(size, GFP_NOFS);
+                if (!value)
+                        return ERR_PTR(-ENOMEM);
+                size = __ceph_getxattr(inode, name, value, size);
+        }
+
+        if (size > 0)
+                acl = posix_acl_from_xattr(&init_user_ns, value, size);
+        else if (size == -ERANGE || size == -ENODATA || size == 0)
+                acl = NULL;
+        else
+                acl = ERR_PTR(-EIO);
+
+        kfree(value);
+
+        if (!IS_ERR(acl))
+                ceph_set_cached_acl(inode, type, acl);
+
+        return acl;
+}
+
+static int ceph_set_acl(struct dentry *dentry, struct inode *inode,
+                                struct posix_acl *acl, int type)
+{
+        int ret = 0, size = 0;
+        const char *name = NULL;
+        char *value = NULL;
+        struct iattr newattrs;
+        umode_t new_mode = inode->i_mode, old_mode = inode->i_mode;
+
+        if (acl) {
+                ret = posix_acl_valid(acl);
+                if (ret < 0)
+                        goto out;
+        }
+
+        switch (type) {
+        case ACL_TYPE_ACCESS:
+                name = POSIX_ACL_XATTR_ACCESS;
+                if (acl) {
+                        ret = posix_acl_equiv_mode(acl, &new_mode);
+                        if (ret < 0)
+                                goto out;
+                        if (ret == 0)
+                                acl = NULL;
+                }
+                break;
+        case ACL_TYPE_DEFAULT:
+                if (!S_ISDIR(inode->i_mode)) {
+                        ret = acl ? -EINVAL : 0;
+                        goto out;
+                }
+                name = POSIX_ACL_XATTR_DEFAULT;
+                break;
+        default:
+                ret = -EINVAL;
+                goto out;
+        }
+
+        if (acl) {
+                size = posix_acl_xattr_size(acl->a_count);
+                value = kmalloc(size, GFP_NOFS);
+                if (!value) {
+                        ret = -ENOMEM;
+                        goto out;
+                }
+
+                ret = posix_acl_to_xattr(&init_user_ns, acl, value, size);
+                if (ret < 0)
+                        goto out_free;
+        }
+
+        if (new_mode != old_mode) {
+                newattrs.ia_mode = new_mode;
+                newattrs.ia_valid = ATTR_MODE;
+                ret = ceph_setattr(dentry, &newattrs);
+                if (ret)
+                        goto out_free;
+        }
+
+        if (value)
+                ret = __ceph_setxattr(dentry, name, value, size, 0);
+        else
+                ret = __ceph_removexattr(dentry, name);
+
+        if (ret) {
+                if (new_mode != old_mode) {
+                        newattrs.ia_mode = old_mode;
+                        newattrs.ia_valid = ATTR_MODE;
+                        ceph_setattr(dentry, &newattrs);
+                }
+                goto out_free;
+        }
+
+        ceph_set_cached_acl(inode, type, acl);
+
+out_free:
+        kfree(value);
+out:
+        return ret;
+}
+
+int ceph_init_acl(struct dentry *dentry, struct inode *inode, struct inode *dir)
+{
+        struct posix_acl *acl = NULL;
+        int ret = 0;
+
+        if (!S_ISLNK(inode->i_mode)) {
+                if (IS_POSIXACL(dir)) {
+                        acl = ceph_get_acl(dir, ACL_TYPE_DEFAULT);
+                        if (IS_ERR(acl)) {
+                                ret = PTR_ERR(acl);
+                                goto out;
+                        }
+                }
+
+                if (!acl)
+                        inode->i_mode &= ~current_umask();
+        }
+
+        if (IS_POSIXACL(dir) && acl) {
+                if (S_ISDIR(inode->i_mode)) {
+                        ret = ceph_set_acl(dentry, inode, acl,
+                                                ACL_TYPE_DEFAULT);
+                        if (ret)
+                                goto out_release;
+                }
+                ret = posix_acl_create(&acl, GFP_NOFS, &inode->i_mode);
+                if (ret < 0)
+                        goto out;
+                else if (ret > 0)
+                        ret = ceph_set_acl(dentry, inode, acl, ACL_TYPE_ACCESS);
+                else
+                        cache_no_acl(inode);
+        } else {
+                cache_no_acl(inode);
+        }
+
+out_release:
+        posix_acl_release(acl);
+out:
+        return ret;
+}
+
+int ceph_acl_chmod(struct dentry *dentry, struct inode *inode)
+{
+        struct posix_acl *acl;
+        int ret = 0;
+
+        if (S_ISLNK(inode->i_mode)) {
+                ret = -EOPNOTSUPP;
+                goto out;
+        }
+
+        if (!IS_POSIXACL(inode))
+                goto out;
+
+        acl = ceph_get_acl(inode, ACL_TYPE_ACCESS);
+        if (IS_ERR_OR_NULL(acl)) {
+                ret = PTR_ERR(acl);
+                goto out;
+        }
+
+        ret = posix_acl_chmod(&acl, GFP_KERNEL, inode->i_mode);
+        if (ret)
+                goto out;
+        ret = ceph_set_acl(dentry, inode, acl, ACL_TYPE_ACCESS);
+        posix_acl_release(acl);
+out:
+        return ret;
+}
+
+static int ceph_xattr_acl_get(struct dentry *dentry, const char *name,
+                                void *value, size_t size, int type)
+{
+        struct posix_acl *acl;
+        int ret = 0;
+
+        if (!IS_POSIXACL(dentry->d_inode))
+                return -EOPNOTSUPP;
+
+        acl = ceph_get_acl(dentry->d_inode, type);
+        if (IS_ERR(acl))
+                return PTR_ERR(acl);
+        if (acl == NULL)
+                return -ENODATA;
+
+        ret = posix_acl_to_xattr(&init_user_ns, acl, value, size);
+        posix_acl_release(acl);
+
+        return ret;
+}
+
+static int ceph_xattr_acl_set(struct dentry *dentry, const char *name,
+                        const void *value, size_t size, int flags, int type)
+{
+        int ret = 0;
+        struct posix_acl *acl = NULL;
+
+        if (!inode_owner_or_capable(dentry->d_inode)) {
+                ret = -EPERM;
+                goto out;
+        }
+
+        if (!IS_POSIXACL(dentry->d_inode)) {
+                ret = -EOPNOTSUPP;
+                goto out;
+        }
+
+        if (value) {
+                acl = posix_acl_from_xattr(&init_user_ns, value, size);
+                if (IS_ERR(acl)) {
+                        ret = PTR_ERR(acl);
+                        goto out;
+                }
+
+                if (acl) {
+                        ret = posix_acl_valid(acl);
+                        if (ret)
+                                goto out_release;
+                }
+        }
+
+        ret = ceph_set_acl(dentry, dentry->d_inode, acl, type);
+
+out_release:
+        posix_acl_release(acl);
+out:
+        return ret;
+}
+
+const struct xattr_handler ceph_xattr_acl_default_handler = {
+        .prefix = POSIX_ACL_XATTR_DEFAULT,
+        .flags  = ACL_TYPE_DEFAULT,
+        .get    = ceph_xattr_acl_get,
+        .set    = ceph_xattr_acl_set,
+};
+
+const struct xattr_handler ceph_xattr_acl_access_handler = {
+        .prefix = POSIX_ACL_XATTR_ACCESS,
+        .flags  = ACL_TYPE_ACCESS,
+        .get    = ceph_xattr_acl_get,
+        .set    = ceph_xattr_acl_set,
+};
diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index 3c0a4bd74996..9289c6b2f1bb 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -2464,6 +2464,7 @@ static void handle_cap_grant(struct inode *inode, struct ceph_mds_caps *grant,
                                 ceph_buffer_put(ci->i_xattrs.blob);
                         ci->i_xattrs.blob = ceph_buffer_get(xattr_buf);
                         ci->i_xattrs.version = version;
+                        ceph_forget_all_cached_acls(inode);
                 }
         }
 
diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
index 2a0bcaeb189a..b629e9d59a35 100644
--- a/fs/ceph/dir.c
+++ b/fs/ceph/dir.c
@@ -693,6 +693,10 @@ static int ceph_mknod(struct inode *dir, struct dentry *dentry,
         if (!err && !req->r_reply_info.head->is_dentry)
                 err = ceph_handle_notrace_create(dir, dentry);
         ceph_mdsc_put_request(req);
+
+        if (!err)
+                err = ceph_init_acl(dentry, dentry->d_inode, dir);
+
         if (err)
                 d_drop(dentry);
         return err;
@@ -1293,6 +1297,7 @@ const struct inode_operations ceph_dir_iops = {
         .getxattr = ceph_getxattr,
         .listxattr = ceph_listxattr,
         .removexattr = ceph_removexattr,
+        .get_acl = ceph_get_acl,
         .mknod = ceph_mknod,
         .symlink = ceph_symlink,
         .mkdir = ceph_mkdir,
diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index d37b2dc01d3f..a808bfb8d8d8 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -95,6 +95,7 @@ const struct inode_operations ceph_file_iops = {
         .getxattr = ceph_getxattr,
         .listxattr = ceph_listxattr,
         .removexattr = ceph_removexattr,
+        .get_acl = ceph_get_acl,
 };
 
 
@@ -680,6 +681,7 @@ static int fill_inode(struct inode *inode,
                         memcpy(ci->i_xattrs.blob->vec.iov_base,
                                iinfo->xattr_data, iinfo->xattr_len);
                 ci->i_xattrs.version = le64_to_cpu(info->xattr_version);
+                ceph_forget_all_cached_acls(inode);
                 xattr_blob = NULL;
         }
 
@@ -1612,6 +1614,7 @@ static const struct inode_operations ceph_symlink_iops = {
         .getxattr = ceph_getxattr,
         .listxattr = ceph_listxattr,
         .removexattr = ceph_removexattr,
+        .get_acl = ceph_get_acl,
 };
 
 /*
@@ -1685,6 +1688,7 @@ int ceph_setattr(struct dentry *dentry, struct iattr *attr)
                         dirtied |= CEPH_CAP_AUTH_EXCL;
                 } else if ((issued & CEPH_CAP_AUTH_SHARED) == 0 ||
                            attr->ia_mode != inode->i_mode) {
+                        inode->i_mode = attr->ia_mode;
                         req->r_args.setattr.mode = cpu_to_le32(attr->ia_mode);
                         mask |= CEPH_SETATTR_MODE;
                         release |= CEPH_CAP_AUTH_SHARED;
@@ -1800,6 +1804,12 @@ int ceph_setattr(struct dentry *dentry, struct iattr *attr)
         if (inode_dirty_flags)
                 __mark_inode_dirty(inode, inode_dirty_flags);
 
+        if (ia_valid & ATTR_MODE) {
+                err = ceph_acl_chmod(dentry, inode);
+                if (err)
+                        goto out_put;
+        }
+
         if (mask) {
                 req->r_inode = inode;
                 ihold(inode);
@@ -1819,6 +1829,7 @@ int ceph_setattr(struct dentry *dentry, struct iattr *attr)
         return err;
 out:
         spin_unlock(&ci->i_ceph_lock);
+out_put:
         ceph_mdsc_put_request(req);
         return err;
 }
diff --git a/fs/ceph/super.c b/fs/ceph/super.c
index e58bd4a23bfb..c6740e43a351 100644
--- a/fs/ceph/super.c
+++ b/fs/ceph/super.c
@@ -819,7 +819,11 @@ static int ceph_set_super(struct super_block *s, void *data)
 
         s->s_flags = fsc->mount_options->sb_flags;
         s->s_maxbytes = 1ULL << 40;  /* temp value until we get mdsmap */
+#ifdef CONFIG_CEPH_FS_POSIX_ACL
+        s->s_flags |= MS_POSIXACL;
+#endif
 
+        s->s_xattr = ceph_xattr_handlers;
         s->s_fs_info = fsc;
         fsc->sb = s;
 
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index 8de94b564d67..7fa78a7c8894 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -335,7 +335,6 @@ struct ceph_inode_info {
         u32 i_fscache_gen; /* sequence, for delayed fscache validate */
         struct work_struct i_revalidate_work;
 #endif
-
         struct inode vfs_inode; /* at end */
 };
 
@@ -725,6 +724,9 @@ extern int ceph_getattr(struct vfsmount *mnt, struct dentry *dentry,
 /* xattr.c */
 extern int ceph_setxattr(struct dentry *, const char *, const void *,
                          size_t, int);
+int __ceph_setxattr(struct dentry *, const char *, const void *, size_t, int);
+ssize_t __ceph_getxattr(struct inode *, const char *, void *, size_t);
+int __ceph_removexattr(struct dentry *, const char *);
 extern ssize_t ceph_getxattr(struct dentry *, const char *, void *, size_t);
 extern ssize_t ceph_listxattr(struct dentry *, char *, size_t);
 extern int ceph_removexattr(struct dentry *, const char *);
@@ -733,6 +735,39 @@ extern void __ceph_destroy_xattrs(struct ceph_inode_info *ci);
 extern void __init ceph_xattr_init(void);
 extern void ceph_xattr_exit(void);
 
+/* acl.c */
+extern const struct xattr_handler ceph_xattr_acl_access_handler;
+extern const struct xattr_handler ceph_xattr_acl_default_handler;
+extern const struct xattr_handler *ceph_xattr_handlers[];
+
+#ifdef CONFIG_CEPH_FS_POSIX_ACL
+
+struct posix_acl *ceph_get_acl(struct inode *, int);
+int ceph_init_acl(struct dentry *, struct inode *, struct inode *);
+int ceph_acl_chmod(struct dentry *, struct inode *);
+void ceph_forget_all_cached_acls(struct inode *inode);
+
+#else
+
+#define ceph_get_acl NULL
+
+static inline int ceph_init_acl(struct dentry *dentry, struct inode *inode,
+                                struct inode *dir)
+{
+        return 0;
+}
+
+static inline int ceph_acl_chmod(struct dentry *dentry, struct inode *inode)
+{
+        return 0;
+}
+
+static inline void ceph_forget_all_cached_acls(struct inode *inode)
+{
+}
+
+#endif
+
 /* caps.c */
 extern const char *ceph_cap_string(int c);
 extern void ceph_handle_caps(struct ceph_mds_session *session,
diff --git a/fs/ceph/xattr.c b/fs/ceph/xattr.c
index be661d8f532a..c7581f3733c1 100644
--- a/fs/ceph/xattr.c
+++ b/fs/ceph/xattr.c
@@ -11,11 +11,24 @@
 #define XATTR_CEPH_PREFIX "ceph."
 #define XATTR_CEPH_PREFIX_LEN (sizeof (XATTR_CEPH_PREFIX) - 1)
 
+/*
+ * List of handlers for synthetic system.* attributes. Other
+ * attributes are handled directly.
+ */
+const struct xattr_handler *ceph_xattr_handlers[] = {
+#ifdef CONFIG_CEPH_FS_POSIX_ACL
+        &ceph_xattr_acl_access_handler,
+        &ceph_xattr_acl_default_handler,
+#endif
+        NULL,
+};
+
 static bool ceph_is_valid_xattr(const char *name)
 {
         return !strncmp(name, XATTR_CEPH_PREFIX, XATTR_CEPH_PREFIX_LEN) ||
                !strncmp(name, XATTR_SECURITY_PREFIX,
                         XATTR_SECURITY_PREFIX_LEN) ||
+               !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN) ||
                !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) ||
                !strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN);
 }
@@ -663,10 +676,9 @@ void __ceph_build_xattrs_blob(struct ceph_inode_info *ci)
         }
 }
 
-ssize_t ceph_getxattr(struct dentry *dentry, const char *name, void *value,
+ssize_t __ceph_getxattr(struct inode *inode, const char *name, void *value,
                       size_t size)
 {
-        struct inode *inode = dentry->d_inode;
         struct ceph_inode_info *ci = ceph_inode(inode);
         int err;
         struct ceph_inode_xattr *xattr;
@@ -675,7 +687,6 @@ ssize_t ceph_getxattr(struct dentry *dentry, const char *name, void *value,
         if (!ceph_is_valid_xattr(name))
                 return -ENODATA;
 
-
         /* let's see if a virtual xattr was requested */
         vxattr = ceph_match_vxattr(inode, name);
         if (vxattr && !(vxattr->exists_cb && !vxattr->exists_cb(ci))) {
@@ -725,6 +736,15 @@ out:
         return err;
 }
 
+ssize_t ceph_getxattr(struct dentry *dentry, const char *name, void *value,
+                      size_t size)
+{
+        if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
+                return generic_getxattr(dentry, name, value, size);
+
+        return __ceph_getxattr(dentry->d_inode, name, value, size);
+}
+
 ssize_t ceph_listxattr(struct dentry *dentry, char *names, size_t size)
 {
         struct inode *inode = dentry->d_inode;
@@ -863,8 +883,8 @@ out:
         return err;
 }
 
-int ceph_setxattr(struct dentry *dentry, const char *name,
-                  const void *value, size_t size, int flags)
+int __ceph_setxattr(struct dentry *dentry, const char *name,
+                        const void *value, size_t size, int flags)
 {
         struct inode *inode = dentry->d_inode;
         struct ceph_vxattr *vxattr;
@@ -879,9 +899,6 @@ int ceph_setxattr(struct dentry *dentry, const char *name,
         struct ceph_inode_xattr *xattr = NULL;
         int required_blob_size;
 
-        if (ceph_snap(inode) != CEPH_NOSNAP)
-                return -EROFS;
-
         if (!ceph_is_valid_xattr(name))
                 return -EOPNOTSUPP;
 
@@ -958,6 +975,18 @@ out:
         return err;
 }
 
+int ceph_setxattr(struct dentry *dentry, const char *name,
+                  const void *value, size_t size, int flags)
+{
+        if (ceph_snap(dentry->d_inode) != CEPH_NOSNAP)
+                return -EROFS;
+
+        if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
+                return generic_setxattr(dentry, name, value, size, flags);
+
+        return __ceph_setxattr(dentry, name, value, size, flags);
+}
+
 static int ceph_send_removexattr(struct dentry *dentry, const char *name)
 {
         struct ceph_fs_client *fsc = ceph_sb_to_client(dentry->d_sb);
@@ -984,7 +1013,7 @@ static int ceph_send_removexattr(struct dentry *dentry, const char *name)
         return err;
 }
 
-int ceph_removexattr(struct dentry *dentry, const char *name)
+int __ceph_removexattr(struct dentry *dentry, const char *name)
 {
         struct inode *inode = dentry->d_inode;
         struct ceph_vxattr *vxattr;
@@ -994,9 +1023,6 @@ int ceph_removexattr(struct dentry *dentry, const char *name)
         int required_blob_size;
         int dirty;
 
-        if (ceph_snap(inode) != CEPH_NOSNAP)
-                return -EROFS;
-
         if (!ceph_is_valid_xattr(name))
                 return -EOPNOTSUPP;
 
@@ -1053,3 +1079,13 @@ out:
         return err;
 }
 
+int ceph_removexattr(struct dentry *dentry, const char *name)
+{
+        if (ceph_snap(dentry->d_inode) != CEPH_NOSNAP)
+                return -EROFS;
+
+        if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
+                return generic_removexattr(dentry, name);
+
+        return __ceph_removexattr(dentry, name);
+}