[PATCH v4 1/3] xattr: extract simple_xattr code from tmpfs

From: Aristeu Rozanski
Date: Wed Jul 18 2012 - 14:52:53 EST

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From: Li Zefan <lizefan@xxxxxxxxxx>

Extract in-memory xattr APIs from tmpfs. Will be used by cgroup.

$ size vmlinux.o
text data bss dec hex filename
4658782 880729 5195032 10734543 a3cbcf vmlinux.o
$ size vmlinux.o
text data bss dec hex filename
4658957 880729 5195032 10734718 a3cc7e vmlinux.o

v5:
- no changes
v4:
- move simple_xattrs_free() to fs/xattr.c
v3:
- in kmem_xattrs_free(), reinitialize the list
- use simple_xattr_* prefix
- introduce simple_xattr_add() to prevent direct list usage

Signed-off-by: Li Zefan <lizefan@xxxxxxxxxx>
Signed-off-by: Aristeu Rozanski <aris@xxxxxxxxxx>

---
fs/xattr.c | 200 +++++++++++++++++++++++++++++++++++++++++++++++
include/linux/shmem_fs.h | 3
include/linux/xattr.h | 25 +++++
mm/shmem.c | 171 +++-------------------------------------
4 files changed, 240 insertions(+), 159 deletions(-)

Index: xattr/fs/xattr.c
===================================================================
--- xattr.orig/fs/xattr.c 2012-07-18 14:14:28.673977819 -0400
+++ xattr/fs/xattr.c 2012-07-18 14:14:29.746007233 -0400
@@ -783,3 +783,203 @@
EXPORT_SYMBOL(generic_listxattr);
EXPORT_SYMBOL(generic_setxattr);
EXPORT_SYMBOL(generic_removexattr);
+
+/*
+ * initialize the simple_xattrs structure
+ */
+void simple_xattrs_init(struct simple_xattrs *xattrs)
+{
+ INIT_LIST_HEAD(&xattrs->head);
+ spin_lock_init(&xattrs->lock);
+}
+
+/*
+ * Allocate new xattr and copy in the value; but leave the name to callers.
+ */
+struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
+{
+ struct simple_xattr *new_xattr;
+ size_t len;
+
+ /* wrap around? */
+ len = sizeof(*new_xattr) + size;
+ if (len <= sizeof(*new_xattr))
+ return NULL;
+
+ new_xattr = kmalloc(len, GFP_KERNEL);
+ if (!new_xattr)
+ return NULL;
+
+ new_xattr->size = size;
+ memcpy(new_xattr->value, value, size);
+ return new_xattr;
+}
+
+/*
+ * free all the xattrs
+ */
+void simple_xattrs_free(struct simple_xattrs *xattrs)
+{
+ struct simple_xattr *xattr, *node;
+
+ spin_lock(&xattrs->lock);
+ list_for_each_entry_safe(xattr, node, &xattrs->head, list) {
+ kfree(xattr->name);
+ kfree(xattr);
+ }
+ INIT_LIST_HEAD(&xattrs->head);
+ spin_unlock(&xattrs->lock);
+}
+
+/*
+ * xattr GET operation for in-memory/pseudo filesystems
+ */
+int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
+ void *buffer, size_t size)
+{
+ struct simple_xattr *xattr;
+ int ret = -ENODATA;
+
+ spin_lock(&xattrs->lock);
+ list_for_each_entry(xattr, &xattrs->head, list) {
+ if (strcmp(name, xattr->name))
+ continue;
+
+ ret = xattr->size;
+ if (buffer) {
+ if (size < xattr->size)
+ ret = -ERANGE;
+ else
+ memcpy(buffer, xattr->value, xattr->size);
+ }
+ break;
+ }
+ spin_unlock(&xattrs->lock);
+ return ret;
+}
+
+static int __simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
+ const void *value, size_t size, int flags)
+{
+ struct simple_xattr *xattr;
+ struct simple_xattr *new_xattr = NULL;
+ size_t len;
+ int err = 0;
+
+ /* value == NULL means remove */
+ if (value) {
+ /* wrap around? */
+ len = sizeof(*new_xattr) + size;
+ if (len <= sizeof(*new_xattr))
+ return -ENOMEM;
+
+ new_xattr = kmalloc(len, GFP_KERNEL);
+ if (!new_xattr)
+ return -ENOMEM;
+
+ new_xattr->name = kstrdup(name, GFP_KERNEL);
+ if (!new_xattr->name) {
+ kfree(new_xattr);
+ return -ENOMEM;
+ }
+
+ new_xattr->size = size;
+ memcpy(new_xattr->value, value, size);
+ }
+
+ spin_lock(&xattrs->lock);
+ list_for_each_entry(xattr, &xattrs->head, list) {
+ if (!strcmp(name, xattr->name)) {
+ if (flags & XATTR_CREATE) {
+ xattr = new_xattr;
+ err = -EEXIST;
+ } else if (new_xattr) {
+ list_replace(&xattr->list, &new_xattr->list);
+ } else {
+ list_del(&xattr->list);
+ }
+ goto out;
+ }
+ }
+ if (flags & XATTR_REPLACE) {
+ xattr = new_xattr;
+ err = -ENODATA;
+ } else {
+ list_add(&new_xattr->list, &xattrs->head);
+ xattr = NULL;
+ }
+out:
+ spin_unlock(&xattrs->lock);
+ if (xattr) {
+ kfree(xattr->name);
+ kfree(xattr);
+ }
+ return err;
+
+}
+
+/*
+ * xattr SET operation for in-memory/pseudo filesystems
+ */
+int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
+ const void *value, size_t size, int flags)
+{
+ if (size == 0)
+ value = ""; /* empty EA, do not remove */
+ return __simple_xattr_set(xattrs, name, value, size, flags);
+}
+
+/*
+ * xattr REMOVE operation for in-memory/pseudo filesystems
+ */
+int simple_xattr_remove(struct simple_xattrs *xattrs, const char *name)
+{
+ return __simple_xattr_set(xattrs, name, NULL, 0, XATTR_REPLACE);
+}
+
+static bool xattr_is_trusted(const char *name)
+{
+ return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
+}
+
+/*
+ * xattr LIST operation for in-memory/pseudo filesystems
+ */
+ssize_t simple_xattr_list(struct simple_xattrs *xattrs, char *buffer, size_t size)
+{
+ bool trusted = capable(CAP_SYS_ADMIN);
+ struct simple_xattr *xattr;
+ size_t used = 0;
+
+ spin_lock(&xattrs->lock);
+ list_for_each_entry(xattr, &xattrs->head, list) {
+ size_t len;
+
+ /* skip "trusted." attributes for unprivileged callers */
+ if (!trusted && xattr_is_trusted(xattr->name))
+ continue;
+
+ len = strlen(xattr->name) + 1;
+ used += len;
+ if (buffer) {
+ if (size < used) {
+ used = -ERANGE;
+ break;
+ }
+ memcpy(buffer, xattr->name, len);
+ buffer += len;
+ }
+ }
+ spin_unlock(&xattrs->lock);
+
+ return used;
+}
+
+void simple_xattr_list_add(struct simple_xattrs *xattrs,
+ struct simple_xattr *new_xattr)
+{
+ spin_lock(&xattrs->lock);
+ list_add(&new_xattr->list, &xattrs->head);
+ spin_unlock(&xattrs->lock);
+}
+
Index: xattr/include/linux/shmem_fs.h
===================================================================
--- xattr.orig/include/linux/shmem_fs.h 2012-07-18 14:14:28.673977819 -0400
+++ xattr/include/linux/shmem_fs.h 2012-07-18 14:14:29.750007343 -0400
@@ -5,6 +5,7 @@
#include <linux/mempolicy.h>
#include <linux/pagemap.h>
#include <linux/percpu_counter.h>
+#include <linux/xattr.h>

/* inode in-kernel data */

@@ -18,7 +19,7 @@
};
struct shared_policy policy; /* NUMA memory alloc policy */
struct list_head swaplist; /* chain of maybes on swap */
- struct list_head xattr_list; /* list of shmem_xattr */
+ struct simple_xattrs xattrs; /* list of xattrs */
struct inode vfs_inode;
};

Index: xattr/include/linux/xattr.h
===================================================================
--- xattr.orig/include/linux/xattr.h 2012-07-18 14:14:28.673977819 -0400
+++ xattr/include/linux/xattr.h 2012-07-18 14:14:29.750007343 -0400
@@ -60,6 +60,7 @@
#ifdef __KERNEL__

#include <linux/types.h>
+#include <linux/spinlock.h>

struct inode;
struct dentry;
@@ -96,6 +97,30 @@
char **xattr_value, size_t size, gfp_t flags);
int vfs_xattr_cmp(struct dentry *dentry, const char *xattr_name,
const char *value, size_t size, gfp_t flags);
+
+struct simple_xattrs {
+ struct list_head head;
+ spinlock_t lock;
+};
+
+struct simple_xattr {
+ struct list_head list;
+ char *name;
+ size_t size;
+ char value[0];
+};
+
+void simple_xattrs_init(struct simple_xattrs *xattrs);
+struct simple_xattr *simple_xattr_alloc(const void *value, size_t size);
+void simple_xattrs_free(struct simple_xattrs *xattrs);
+int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
+ void *buffer, size_t size);
+int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
+ const void *value, size_t size, int flags);
+int simple_xattr_remove(struct simple_xattrs *xattrs, const char *name);
+ssize_t simple_xattr_list(struct simple_xattrs *xattrs, char *buffer, size_t size);
+void simple_xattr_list_add(struct simple_xattrs *xattrs, struct simple_xattr *new_xattr);
+
#endif /* __KERNEL__ */

#endif /* _LINUX_XATTR_H */
Index: xattr/mm/shmem.c
===================================================================
--- xattr.orig/mm/shmem.c 2012-07-18 14:14:28.673977819 -0400
+++ xattr/mm/shmem.c 2012-07-18 14:14:29.750007343 -0400
@@ -77,13 +77,6 @@
/* Symlink up to this size is kmalloc'ed instead of using a swappable page */
#define SHORT_SYMLINK_LEN 128

-struct shmem_xattr {
- struct list_head list; /* anchored by shmem_inode_info->xattr_list */
- char *name; /* xattr name */
- size_t size;
- char value[0];
-};
-
/*
* shmem_fallocate and shmem_writepage communicate via inode->i_private
* (with i_mutex making sure that it has only one user at a time):
@@ -627,7 +620,6 @@
static void shmem_evict_inode(struct inode *inode)
{
struct shmem_inode_info *info = SHMEM_I(inode);
- struct shmem_xattr *xattr, *nxattr;

if (inode->i_mapping->a_ops == &shmem_aops) {
shmem_unacct_size(info->flags, inode->i_size);
@@ -641,10 +633,7 @@
} else
kfree(info->symlink);

- list_for_each_entry_safe(xattr, nxattr, &info->xattr_list, list) {
- kfree(xattr->name);
- kfree(xattr);
- }
+ simple_xattrs_free(&info->xattrs);
BUG_ON(inode->i_blocks);
shmem_free_inode(inode->i_sb);
clear_inode(inode);
@@ -1360,7 +1349,7 @@
spin_lock_init(&info->lock);
info->flags = flags & VM_NORESERVE;
INIT_LIST_HEAD(&info->swaplist);
- INIT_LIST_HEAD(&info->xattr_list);
+ simple_xattrs_init(&info->xattrs);
cache_no_acl(inode);

switch (mode & S_IFMT) {
@@ -2134,28 +2123,6 @@
*/

/*
- * Allocate new xattr and copy in the value; but leave the name to callers.
- */
-static struct shmem_xattr *shmem_xattr_alloc(const void *value, size_t size)
-{
- struct shmem_xattr *new_xattr;
- size_t len;
-
- /* wrap around? */
- len = sizeof(*new_xattr) + size;
- if (len <= sizeof(*new_xattr))
- return NULL;
-
- new_xattr = kmalloc(len, GFP_KERNEL);
- if (!new_xattr)
- return NULL;
-
- new_xattr->size = size;
- memcpy(new_xattr->value, value, size);
- return new_xattr;
-}
-
-/*
* Callback for security_inode_init_security() for acquiring xattrs.
*/
static int shmem_initxattrs(struct inode *inode,
@@ -2164,11 +2131,11 @@
{
struct shmem_inode_info *info = SHMEM_I(inode);
const struct xattr *xattr;
- struct shmem_xattr *new_xattr;
+ struct simple_xattr *new_xattr;
size_t len;

for (xattr = xattr_array; xattr->name != NULL; xattr++) {
- new_xattr = shmem_xattr_alloc(xattr->value, xattr->value_len);
+ new_xattr = simple_xattr_alloc(xattr->value, xattr->value_len);
if (!new_xattr)
return -ENOMEM;

@@ -2185,91 +2152,12 @@
memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
xattr->name, len);

- spin_lock(&info->lock);
- list_add(&new_xattr->list, &info->xattr_list);
- spin_unlock(&info->lock);
+ simple_xattr_list_add(&info->xattrs, new_xattr);
}

return 0;
}

-static int shmem_xattr_get(struct dentry *dentry, const char *name,
- void *buffer, size_t size)
-{
- struct shmem_inode_info *info;
- struct shmem_xattr *xattr;
- int ret = -ENODATA;
-
- info = SHMEM_I(dentry->d_inode);
-
- spin_lock(&info->lock);
- list_for_each_entry(xattr, &info->xattr_list, list) {
- if (strcmp(name, xattr->name))
- continue;
-
- ret = xattr->size;
- if (buffer) {
- if (size < xattr->size)
- ret = -ERANGE;
- else
- memcpy(buffer, xattr->value, xattr->size);
- }
- break;
- }
- spin_unlock(&info->lock);
- return ret;
-}
-
-static int shmem_xattr_set(struct inode *inode, const char *name,
- const void *value, size_t size, int flags)
-{
- struct shmem_inode_info *info = SHMEM_I(inode);
- struct shmem_xattr *xattr;
- struct shmem_xattr *new_xattr = NULL;
- int err = 0;
-
- /* value == NULL means remove */
- if (value) {
- new_xattr = shmem_xattr_alloc(value, size);
- if (!new_xattr)
- return -ENOMEM;
-
- new_xattr->name = kstrdup(name, GFP_KERNEL);
- if (!new_xattr->name) {
- kfree(new_xattr);
- return -ENOMEM;
- }
- }
-
- spin_lock(&info->lock);
- list_for_each_entry(xattr, &info->xattr_list, list) {
- if (!strcmp(name, xattr->name)) {
- if (flags & XATTR_CREATE) {
- xattr = new_xattr;
- err = -EEXIST;
- } else if (new_xattr) {
- list_replace(&xattr->list, &new_xattr->list);
- } else {
- list_del(&xattr->list);
- }
- goto out;
- }
- }
- if (flags & XATTR_REPLACE) {
- xattr = new_xattr;
- err = -ENODATA;
- } else {
- list_add(&new_xattr->list, &info->xattr_list);
- xattr = NULL;
- }
-out:
- spin_unlock(&info->lock);
- if (xattr)
- kfree(xattr->name);
- kfree(xattr);
- return err;
-}
-
static const struct xattr_handler *shmem_xattr_handlers[] = {
#ifdef CONFIG_TMPFS_POSIX_ACL
&generic_acl_access_handler,
@@ -2300,6 +2188,7 @@
static ssize_t shmem_getxattr(struct dentry *dentry, const char *name,
void *buffer, size_t size)
{
+ struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
int err;

/*
@@ -2314,12 +2203,13 @@
if (err)
return err;

- return shmem_xattr_get(dentry, name, buffer, size);
+ return simple_xattr_get(&info->xattrs, name, buffer, size);
}

static int shmem_setxattr(struct dentry *dentry, const char *name,
const void *value, size_t size, int flags)
{
+ struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
int err;

/*
@@ -2334,15 +2224,12 @@
if (err)
return err;

- if (size == 0)
- value = ""; /* empty EA, do not remove */
-
- return shmem_xattr_set(dentry->d_inode, name, value, size, flags);
-
+ return simple_xattr_set(&info->xattrs, name, value, size, flags);
}

static int shmem_removexattr(struct dentry *dentry, const char *name)
{
+ struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
int err;

/*
@@ -2357,45 +2244,13 @@
if (err)
return err;

- return shmem_xattr_set(dentry->d_inode, name, NULL, 0, XATTR_REPLACE);
-}
-
-static bool xattr_is_trusted(const char *name)
-{
- return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
+ return simple_xattr_remove(&info->xattrs, name);
}

static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
{
- bool trusted = capable(CAP_SYS_ADMIN);
- struct shmem_xattr *xattr;
- struct shmem_inode_info *info;
- size_t used = 0;
-
- info = SHMEM_I(dentry->d_inode);
-
- spin_lock(&info->lock);
- list_for_each_entry(xattr, &info->xattr_list, list) {
- size_t len;
-
- /* skip "trusted." attributes for unprivileged callers */
- if (!trusted && xattr_is_trusted(xattr->name))
- continue;
-
- len = strlen(xattr->name) + 1;
- used += len;
- if (buffer) {
- if (size < used) {
- used = -ERANGE;
- break;
- }
- memcpy(buffer, xattr->name, len);
- buffer += len;
- }
- }
- spin_unlock(&info->lock);
-
- return used;
+ struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
+ return simple_xattr_list(&info->xattrs, buffer, size);
}
#endif /* CONFIG_TMPFS_XATTR */

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Next message: Aristeu Rozanski: "[PATCH v4 2/3] cgroup: revise how we re-populate root directory"
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