Re: [PATCH v4] ceph: add acl for cephfs

[Li Wang <liwang@xxxxxxxxxxxxxxx>]

Hi,
  It seems to me there are three issues, you can take a look below if 
they are really there,

On 11/08/2013 01:23 PM, Guangliang Zhao wrote:
> v4: check the validity before set/get_cached_acl()
>
> v3: handle the attr change in ceph_set_acl()
>
> v2: remove some redundant code in ceph_setattr()
>
> Signed-off-by: Guangliang Zhao <lucienchao@xxxxxxxxx>
> ---
>   fs/ceph/Kconfig  |   13 +++
>   fs/ceph/Makefile |    1 +
>   fs/ceph/acl.c    |  326 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>   fs/ceph/dir.c    |    5 +
>   fs/ceph/inode.c  |   14 +++
>   fs/ceph/super.c  |    4 +
>   fs/ceph/super.h  |   35 ++++++
>   fs/ceph/xattr.c  |   60 ++++++++--
>   8 files changed, 446 insertions(+), 12 deletions(-)
>   create mode 100644 fs/ceph/acl.c
>
> diff --git a/fs/ceph/Kconfig b/fs/ceph/Kconfig
> index ac9a2ef..264e9bf 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 32e3010..85a4230 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 0000000..a474626
> --- /dev/null
> +++ b/fs/ceph/acl.c
> @@ -0,0 +1,326 @@
> +/*
> + * linux/fs/ceph/acl.c
> + *
> + * Copyright (C) 2013 Guangliang Zhao, <lucienchao@xxxxxxxxx>
> + *
> + * 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);
> +	int issued;
> +
> +	spin_lock(&ci->i_ceph_lock);
> +	issued = __ceph_caps_issued(ci, NULL);
> +	if (issued & (CEPH_CAP_XATTR_EXCL | CEPH_CAP_XATTR_SHARED)) {
> +		set_cached_acl(inode, type, acl);
> +		ci->i_aclcache_gen = ci->i_rdcache_gen;
> +	}
> +	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 = NULL;
> +
> +	spin_lock(&ci->i_ceph_lock);
> +	if (ci->i_aclcache_gen == ci->i_rdcache_gen)
> +		acl = get_cached_acl(inode, type);
> +	spin_unlock(&ci->i_ceph_lock);
> +
> +	return acl;
> +}
> +
> +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;

If client does not own cap, it can not rely on the cached acl, in that 
case, ceph_get_cached_acl() will return NULL rather than ACL_NOT_CACHED.
It will forbid to do the following synchronous MDS consultation.

> +
> +	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;
> +
> +	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 != inode->i_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)
> +		goto out_free;

I am not sure if there is a situation that ceph_setattr() and 
ceph_setxattr() both need be invoked. If so, and the former succeeds, 
the latter gets error, should we roll back the ceph_setattr()?

And, if acl == NULL, thus value == NULL, after calling 
ceph_removexattr(), should we invoke forget_cached_acl()? 
forget_cached_acl() leaves the acl be ACL_NOT_CACHED rather than NULL, i 
am not sure if the designer of VFS acl accepts that acl be NULL in the 
cache, since ceph_set_cached_acl() below will let acl in the cache to be 
NULL

> +
> +	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/dir.c b/fs/ceph/dir.c
> index 2a0bcae..b629e9d 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 2ae1381..4021ef0 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,
>   };
>
>
> @@ -366,6 +367,10 @@ struct inode *ceph_alloc_inode(struct super_block *sb)
>   	ci->i_rdcache_gen = 0;
>   	ci->i_rdcache_revoking = 0;
>
> +#ifdef CONFIG_CEPH_FS_POSIX_ACL
> +	ci->i_aclcache_gen = 0;
> +#endif
> +
>   	INIT_LIST_HEAD(&ci->i_unsafe_writes);
>   	INIT_LIST_HEAD(&ci->i_unsafe_dirops);
>   	spin_lock_init(&ci->i_unsafe_lock);
> @@ -1632,6 +1637,7 @@ static const struct inode_operations ceph_symlink_iops = {
>   	.getxattr = ceph_getxattr,
>   	.listxattr = ceph_listxattr,
>   	.removexattr = ceph_removexattr,
> +	.get_acl = ceph_get_acl,
>   };
>
>   /*
> @@ -1705,6 +1711,7 @@ 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;
> @@ -1820,6 +1827,12 @@ 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);
> @@ -1839,6 +1852,7 @@ 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 e58bd4a..c6740e4 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 8de94b5..dbcd4d2 100644
> --- a/fs/ceph/super.h
> +++ b/fs/ceph/super.h
> @@ -336,6 +336,10 @@ struct ceph_inode_info {
>   	struct work_struct i_revalidate_work;
>   #endif
>
> +#ifdef CONFIG_CEPH_FS_POSIX_ACL
> +	u32 i_aclcache_gen;
> +#endif
> +
>   	struct inode vfs_inode; /* at end */
>   };
>
> @@ -725,6 +729,9 @@ 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 +740,34 @@ 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 *);
> +
> +#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;
> +}
> +
> +#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 be661d8..c7581f3 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);
> +}
--
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