* as practically no size limit on the file, and the extended
* attributes permissions may differ from those of the parent file.
* This interface is really quite clever, but it's also completely
- * different than what is supported on Linux.
+ * different than what is supported on Linux. It also comes with a
+ * steep performance penalty when accessing small xattrs because they
+ * are not stored with the parent file.
*
* Under Linux extended attributes are manipulated by the system
* calls getxattr(2), setxattr(2), and listxattr(2). They consider
* extended attributes to be name/value pairs where the name is a
* NULL terminated string. The name must also include one of the
- * following name space prefixes:
+ * following namespace prefixes:
*
* user - No restrictions and is available to user applications.
* trusted - Restricted to kernel and root (CAP_SYS_ADMIN) use.
* system - Used for access control lists (system.nfs4_acl, etc).
* security - Used by SELinux to store a files security context.
*
- * This Linux interface is implemented internally using the more
- * flexible Solaris style extended attributes. Every extended
- * attribute is store as a file in a hidden directory associated
- * with the parent file. This ensures on disk compatibility with
- * zfs implementations on other platforms (Solaris, FreeBSD, MacOS).
+ * The value under Linux to limited to 65536 bytes of binary data.
+ * In practice, individual xattrs tend to be much smaller than this
+ * and are typically less than 100 bytes. A good example of this
+ * are the security.selinux xattrs which are less than 100 bytes and
+ * exist for every file when xattr labeling is enabled.
*
- * One consequence of this implementation is that when an extended
- * attribute is manipulated an inode is created. This inode will
- * exist in the Linux inode cache but there will be no associated
- * entry in the dentry cache which references it. This is safe
- * but it may result in some confusion.
+ * The Linux xattr implemenation has been written to take advantage of
+ * this typical usage. When the dataset property 'xattr=sa' is set,
+ * then xattrs will be preferentially stored as System Attributes (SA).
+ * This allows tiny xattrs (~100 bytes) to be stored with the dnode and
+ * up to 64k of xattrs to be stored in the spill block. If additional
+ * xattr space is required, which is unlikely under Linux, they will
+ * be stored using the traditional directory approach.
*
- * Longer term I would like to see the 'security.selinux' extended
- * attribute moved to a SA. This should significantly improve
- * performance on a SELinux enabled system by minimizing the
- * number of seeks required to access a file. However, for now
- * this xattr is still stored in a file because I'm pretty sure
- * adding a new SA will break on-disk compatibility.
+ * This optimization results in roughly a 3x performance improvement
+ * when accessing xattrs because it avoids the need to perform a seek
+ * for every xattr value. When multiple xattrs are stored per-file
+ * the performance improvements are even greater because all of the
+ * xattrs stored in the spill block will be cached.
+ *
+ * However, by default SA based xattrs are disabled in the Linux port
+ * to maximize compatibility with other implementations. If you do
+ * enable SA based xattrs then they will not be visible on platforms
+ * which do not support this feature.
+ *
+ * NOTE: One additional consequence of the xattr directory implementation
+ * is that when an extended attribute is manipulated an inode is created.
+ * This inode will exist in the Linux inode cache but there will be no
+ * associated entry in the dentry cache which references it. This is
+ * safe but it may result in some confusion. Enabling SA based xattrs
+ * largely avoids the issue except in the overflow case.
*/
-
#include <sys/zfs_vfsops.h>
#include <sys/zfs_vnops.h>
#include <sys/zfs_znode.h>
return (0);
}
-ssize_t
-zpl_xattr_list(struct dentry *dentry, char *buffer, size_t buffer_size)
+static ssize_t
+zpl_xattr_list_dir(xattr_filldir_t *xf, cred_t *cr)
{
- struct inode *ip = dentry->d_inode;
+ struct inode *ip = xf->inode;
struct inode *dxip = NULL;
loff_t pos = 3; /* skip '.', '..', and '.zfs' entries. */
- cred_t *cr = CRED();
int error;
- xattr_filldir_t xf = { buffer_size, 0, buffer, ip };
-
- crhold(cr);
/* Lookup the xattr directory */
error = -zfs_lookup(ip, NULL, &dxip, LOOKUP_XATTR, cr, NULL, NULL);
if (error == -ENOENT)
error = 0;
- goto out;
+ return (error);
}
/* Fill provided buffer via zpl_zattr_filldir helper */
- error = -zfs_readdir(dxip, (void *)&xf, zpl_xattr_filldir, &pos, cr);
+ error = -zfs_readdir(dxip, (void *)xf, zpl_xattr_filldir, &pos, cr);
+ iput(dxip);
+
+ return (error);
+}
+
+static ssize_t
+zpl_xattr_list_sa(xattr_filldir_t *xf)
+{
+ znode_t *zp = ITOZ(xf->inode);
+ nvpair_t *nvp = NULL;
+ int error = 0;
+
+ mutex_enter(&zp->z_lock);
+ if (zp->z_xattr_cached == NULL)
+ error = -zfs_sa_get_xattr(zp);
+ mutex_exit(&zp->z_lock);
+
+ if (error)
+ return (error);
+
+ ASSERT(zp->z_xattr_cached);
+
+ while ((nvp = nvlist_next_nvpair(zp->z_xattr_cached, nvp)) != NULL) {
+ ASSERT3U(nvpair_type(nvp), ==, DATA_TYPE_BYTE_ARRAY);
+
+ error = zpl_xattr_filldir((void *)xf, nvpair_name(nvp),
+ strlen(nvpair_name(nvp)), 0, 0, 0);
+ if (error)
+ return (error);
+ }
+
+ return (0);
+}
+
+ssize_t
+zpl_xattr_list(struct dentry *dentry, char *buffer, size_t buffer_size)
+{
+ znode_t *zp = ITOZ(dentry->d_inode);
+ zfs_sb_t *zsb = ZTOZSB(zp);
+ xattr_filldir_t xf = { buffer_size, 0, buffer, dentry->d_inode };
+ cred_t *cr = CRED();
+ int error = 0;
+
+ crhold(cr);
+ rw_enter(&zp->z_xattr_lock, RW_READER);
+
+ if (zsb->z_use_sa && zp->z_is_sa) {
+ error = zpl_xattr_list_sa(&xf);
+ if (error)
+ goto out;
+ }
+
+ error = zpl_xattr_list_dir(&xf, cr);
if (error)
goto out;
error = xf.offset;
out:
- if (dxip)
- iput(dxip);
+ rw_exit(&zp->z_xattr_lock);
crfree(cr);
return (error);
}
static int
-zpl_xattr_get(struct inode *ip, const char *name, void *buf, size_t size)
+zpl_xattr_get_dir(struct inode *ip, const char *name, void *value,
+ size_t size, cred_t *cr)
{
struct inode *dxip = NULL;
struct inode *xip = NULL;
- cred_t *cr = CRED();
int error;
- crhold(cr);
-
/* Lookup the xattr directory */
error = -zfs_lookup(ip, NULL, &dxip, LOOKUP_XATTR, cr, NULL, NULL);
if (error)
goto out;
}
- error = zpl_read_common(xip, buf, size, 0, UIO_SYSSPACE, 0, cr);
+ error = zpl_read_common(xip, value, size, 0, UIO_SYSSPACE, 0, cr);
out:
if (xip)
iput(xip);
if (dxip)
iput(dxip);
- crfree(cr);
+ return (error);
+}
+
+static int
+zpl_xattr_get_sa(struct inode *ip, const char *name, void *value, size_t size)
+{
+ znode_t *zp = ITOZ(ip);
+ uchar_t *nv_value;
+ uint_t nv_size;
+ int error = 0;
+ ASSERT(RW_LOCK_HELD(&zp->z_xattr_lock));
+
+ mutex_enter(&zp->z_lock);
+ if (zp->z_xattr_cached == NULL)
+ error = -zfs_sa_get_xattr(zp);
+ mutex_exit(&zp->z_lock);
+
+ if (error)
+ return (error);
+
+ ASSERT(zp->z_xattr_cached);
+ error = -nvlist_lookup_byte_array(zp->z_xattr_cached, name,
+ &nv_value, &nv_size);
+ if (error)
+ return (error);
+
+ if (!size)
+ return (nv_size);
+
+ memcpy(value, nv_value, MIN(size, nv_size));
+
+ return (MIN(size, nv_size));
+}
+
+static int
+__zpl_xattr_get(struct inode *ip, const char *name, void *value, size_t size,
+ cred_t *cr)
+{
+ znode_t *zp = ITOZ(ip);
+ zfs_sb_t *zsb = ZTOZSB(zp);
+ int error;
+
+ ASSERT(RW_LOCK_HELD(&zp->z_xattr_lock));
+
+ if (zsb->z_use_sa && zp->z_is_sa) {
+ error = zpl_xattr_get_sa(ip, name, value, size);
+ if (error >= 0)
+ goto out;
+ }
+
+ error = zpl_xattr_get_dir(ip, name, value, size, cr);
+out:
if (error == -ENOENT)
error = -ENODATA;
}
static int
-zpl_xattr_set(struct inode *ip, const char *name, const void *value,
- size_t size, int flags)
+zpl_xattr_get(struct inode *ip, const char *name, void *value, size_t size)
+{
+ znode_t *zp = ITOZ(ip);
+ cred_t *cr = CRED();
+ int error;
+
+ crhold(cr);
+ rw_enter(&zp->z_xattr_lock, RW_READER);
+ error = __zpl_xattr_get(ip, name, value, size, cr);
+ rw_exit(&zp->z_xattr_lock);
+ crfree(cr);
+
+ return (error);
+}
+
+static int
+zpl_xattr_set_dir(struct inode *ip, const char *name, const void *value,
+ size_t size, int flags, cred_t *cr)
{
struct inode *dxip = NULL;
struct inode *xip = NULL;
vattr_t *vap = NULL;
- cred_t *cr = CRED();
ssize_t wrote;
int error;
const int xattr_mode = S_IFREG | 0644;
- crhold(cr);
-
/* Lookup the xattr directory and create it if required. */
error = -zfs_lookup(ip, NULL, &dxip, LOOKUP_XATTR | CREATE_XATTR_DIR,
cr, NULL, NULL);
if (error)
goto out;
- /*
- * Lookup a specific xattr name in the directory, two failure modes:
- * XATTR_CREATE: fail if xattr already exists
- * XATTR_REMOVE: fail if xattr does not exist
- */
+ /* Lookup a specific xattr name in the directory */
error = -zfs_lookup(dxip, (char *)name, &xip, 0, cr, NULL, NULL);
- if (error) {
- if (error != -ENOENT)
- goto out;
+ if (error && (error != -ENOENT))
+ goto out;
- if ((error == -ENOENT) && (flags & XATTR_REPLACE))
- goto out;
- } else {
- error = -EEXIST;
- if (flags & XATTR_CREATE)
- goto out;
- }
error = 0;
/* Remove a specific name xattr when value is set to NULL. */
if (dxip)
iput(dxip);
- crfree(cr);
if (error == -ENOENT)
error = -ENODATA;
return (error);
}
+static int
+zpl_xattr_set_sa(struct inode *ip, const char *name, const void *value,
+ size_t size, int flags, cred_t *cr)
+{
+ znode_t *zp = ITOZ(ip);
+ nvlist_t *nvl;
+ size_t sa_size;
+ int error;
+
+ ASSERT(zp->z_xattr_cached);
+ nvl = zp->z_xattr_cached;
+
+ if (value == NULL) {
+ error = -nvlist_remove(nvl, name, DATA_TYPE_BYTE_ARRAY);
+ if (error == -ENOENT)
+ error = zpl_xattr_set_dir(ip, name, NULL, 0, flags, cr);
+ } else {
+ /* Limited to 32k to keep nvpair memory allocations small */
+ if (size > DXATTR_MAX_ENTRY_SIZE)
+ return (-EFBIG);
+
+ /* Prevent the DXATTR SA from consuming the entire SA region */
+ error = -nvlist_size(nvl, &sa_size, NV_ENCODE_XDR);
+ if (error)
+ return (error);
+
+ if (sa_size > DXATTR_MAX_SA_SIZE)
+ return (-EFBIG);
+
+ error = -nvlist_add_byte_array(nvl, name,
+ (uchar_t *)value, size);
+ if (error)
+ return (error);
+ }
+
+ /* Update the SA for additions, modifications, and removals. */
+ if (!error)
+ error = -zfs_sa_set_xattr(zp);
+
+ ASSERT3S(error, <=, 0);
+
+ return (error);
+}
+
+static int
+zpl_xattr_set(struct inode *ip, const char *name, const void *value,
+ size_t size, int flags)
+{
+ znode_t *zp = ITOZ(ip);
+ zfs_sb_t *zsb = ZTOZSB(zp);
+ cred_t *cr = CRED();
+ int error;
+
+ crhold(cr);
+ rw_enter(&ITOZ(ip)->z_xattr_lock, RW_WRITER);
+
+ /*
+ * Before setting the xattr check to see if it already exists.
+ * This is done to ensure the following optional flags are honored.
+ *
+ * XATTR_CREATE: fail if xattr already exists
+ * XATTR_REPLACE: fail if xattr does not exist
+ */
+ error = __zpl_xattr_get(ip, name, NULL, 0, cr);
+ if (error < 0) {
+ if (error != -ENODATA)
+ goto out;
+
+ if ((error == -ENODATA) && (flags & XATTR_REPLACE))
+ goto out;
+ } else {
+ error = -EEXIST;
+ if (flags & XATTR_CREATE)
+ goto out;
+ }
+
+ /* Preferentially store the xattr as a SA for better performance */
+ if (zsb->z_use_sa && zsb->z_xattr_sa && zp->z_is_sa) {
+ error = zpl_xattr_set_sa(ip, name, value, size, flags, cr);
+ if (error == 0)
+ goto out;
+ }
+
+ error = zpl_xattr_set_dir(ip, name, value, size, flags, cr);
+out:
+ rw_exit(&ITOZ(ip)->z_xattr_lock);
+ crfree(cr);
+ ASSERT3S(error, <=, 0);
+
+ return (error);
+}
+
static int
__zpl_xattr_user_get(struct inode *ip, const char *name,
- void *buffer, size_t size)
+ void *value, size_t size)
{
char *xattr_name;
int error;
return -EOPNOTSUPP;
xattr_name = kmem_asprintf("%s%s", XATTR_USER_PREFIX, name);
- error = zpl_xattr_get(ip, xattr_name, buffer, size);
+ error = zpl_xattr_get(ip, xattr_name, value, size);
strfree(xattr_name);
return (error);
static int
__zpl_xattr_trusted_get(struct inode *ip, const char *name,
- void *buffer, size_t size)
+ void *value, size_t size)
{
char *xattr_name;
int error;
return -EINVAL;
xattr_name = kmem_asprintf("%s%s", XATTR_TRUSTED_PREFIX, name);
- error = zpl_xattr_get(ip, xattr_name, buffer, size);
+ error = zpl_xattr_get(ip, xattr_name, value, size);
strfree(xattr_name);
return (error);
static int
__zpl_xattr_security_get(struct inode *ip, const char *name,
- void *buffer, size_t size)
+ void *value, size_t size)
{
char *xattr_name;
int error;
return -EINVAL;
xattr_name = kmem_asprintf("%s%s", XATTR_SECURITY_PREFIX, name);
- error = zpl_xattr_get(ip, xattr_name, buffer, size);
+ error = zpl_xattr_get(ip, xattr_name, value, size);
strfree(xattr_name);
return (error);
projects / zfs / commitdiff