ZFS fix to make xattr=sa logging to ZIL on xattr create/remove/update.

As such, there are no specific synchronous semantics defined for
the xattrs. But for xattr=on, it does log to ZIL and zil_commit() is
done, if sync=always is set on dataset. This provides sync semantics
for xattr=on with sync=always set on dataset.
For the xattr=sa implementation, it doesn't log to ZIL, so, even with
sync=always, xattrs are not guaranteed to be synced before xattr call
returns to caller. so xattr can be lost if system crash happens, before
txg carrying xattr transaction is synced.

This change makes xattr=sa logging to ZIL on xattr create/remove/update
and xattrs are synced to ZIL (zil_commit() done) for sync=always.
This make xattr=sa behavior similar to xattr=on.

This could also provide basic framework to support implementing sync
semantics at file level for xattr=sa.

Signed-off-by: Jitendra Patidar <jitendra.patidar@nutanix.com>
Closes #8768

cmd/zdb/zdb_il.c

@@ -266,6 +266,32 @@ zil_prt_rec_setattr(zilog_t *zilog, int txtype, const void *arg)
 	}
 }
 
+/* ARGSUSED */
+static void
+zil_prt_rec_setsaxattr(zilog_t *zilog, int txtype, const void *arg)
+{
+	const lr_setsaxattr_t *lr = arg;
+	char	*name;
+	char	*val;
+	int	i;
+
+	name = (char *)(lr + 1);
+	(void) printf("%sfoid %llu\n", tab_prefix,
+	    (u_longlong_t)lr->lr_foid);
+
+	(void) printf("%sXAT_NAME  %s\n", tab_prefix, name);
+	if (lr->lr_size == 0) {
+		(void) printf("%sXAT_VALUE  NULL\n", tab_prefix);
+	} else {
+		(void) printf("%sXAT_VALUE  ", tab_prefix);
+		val = name + (strlen(name) + 1);
+		for (i = 0; i < lr->lr_size; i++) {
+			(void) printf("%c", *val);
+			val++;
+		}
+	}
+}
+
 /* ARGSUSED */
 static void
 zil_prt_rec_acl(zilog_t *zilog, int txtype, const void *arg)
@@ -305,6 +331,8 @@ static zil_rec_info_t zil_rec_info[TX_MAX_TYPE] = {
 	{.zri_print = zil_prt_rec_create,   .zri_name = "TX_MKDIR_ATTR      "},
 	{.zri_print = zil_prt_rec_create,   .zri_name = "TX_MKDIR_ACL_ATTR  "},
 	{.zri_print = zil_prt_rec_write,    .zri_name = "TX_WRITE2          "},
+	{.zri_print = zil_prt_rec_setsaxattr,
+	    .zri_name = "TX_SETSAXATTR      "},
 };
 
 /* ARGSUSED */

cmd/ztest/ztest.c

@@ -2383,6 +2383,7 @@ zil_replay_func_t *ztest_replay_vector[TX_MAX_TYPE] = {
 	NULL,			/* TX_MKDIR_ATTR */
 	NULL,			/* TX_MKDIR_ACL_ATTR */
 	NULL,			/* TX_WRITE2 */
+	NULL,			/* TX_SETSAXATTR */
 };
 
 /*

include/sys/zfs_sa.h

@@ -139,7 +139,7 @@ void zfs_sa_symlink(struct znode *, char *link, int len, dmu_tx_t *);
 void zfs_sa_get_scanstamp(struct znode *, xvattr_t *);
 void zfs_sa_set_scanstamp(struct znode *, xvattr_t *, dmu_tx_t *);
 int zfs_sa_get_xattr(struct znode *);
-int zfs_sa_set_xattr(struct znode *);
+int zfs_sa_set_xattr(struct znode *, const char *, const void *, size_t);
 void zfs_sa_upgrade(struct sa_handle  *, dmu_tx_t *);
 void zfs_sa_upgrade_txholds(dmu_tx_t *, struct znode *);
 void zfs_sa_init(void);

include/sys/zfs_znode.h

@@ -286,6 +286,8 @@ extern void zfs_log_acl(zilog_t *zilog, dmu_tx_t *tx, znode_t *zp,
     vsecattr_t *vsecp, zfs_fuid_info_t *fuidp);
 extern void zfs_xvattr_set(znode_t *zp, xvattr_t *xvap, dmu_tx_t *tx);
 extern void zfs_upgrade(zfsvfs_t *zfsvfs, dmu_tx_t *tx);
+extern void zfs_log_setsaxattr(zilog_t *zilog, dmu_tx_t *tx, int txtype,
+    znode_t *zp, const char *name, const void *value, size_t size);
 
 extern void zfs_znode_update_vfs(struct znode *);
 

include/sys/zil.h

@@ -162,7 +162,8 @@ typedef enum zil_create {
 #define	TX_MKDIR_ATTR		18	/* mkdir with attr */
 #define	TX_MKDIR_ACL_ATTR	19	/* mkdir with ACL + attrs */
 #define	TX_WRITE2		20	/* dmu_sync EALREADY write */
-#define	TX_MAX_TYPE		21	/* Max transaction type */
+#define	TX_SETSAXATTR		21	/* Set sa xattrs on file */
+#define	TX_MAX_TYPE		22	/* Max transaction type */
 
 /*
  * The transactions for mkdir, symlink, remove, rmdir, link, and rename
@@ -182,7 +183,8 @@ typedef enum zil_create {
 	(txtype) == TX_SETATTR ||	\
 	(txtype) == TX_ACL_V0 ||	\
 	(txtype) == TX_ACL ||		\
-	(txtype) == TX_WRITE2)
+	(txtype) == TX_WRITE2 ||	\
+	(txtype) == TX_SETSAXATTR)
 
 /*
  * The number of dnode slots consumed by the object is stored in the 8
@@ -335,6 +337,13 @@ typedef struct {
 	/* optional attribute lr_attr_t may be here */
 } lr_setattr_t;
 
+typedef struct {
+	lr_t		lr_common;	/* common portion of log record */
+	uint64_t	lr_foid;	/* file object to change attributes */
+	uint64_t	lr_size;
+	/* xattr name and value follows */
+} lr_setsaxattr_t;
+
 typedef struct {
 	lr_t		lr_common;	/* common portion of log record */
 	uint64_t	lr_foid;	/* obj id of file */

include/zfeature_common.h

@@ -75,6 +75,7 @@ typedef enum spa_feature {
 	SPA_FEATURE_DEVICE_REBUILD,
 	SPA_FEATURE_ZSTD_COMPRESS,
 	SPA_FEATURE_DRAID,
+	SPA_FEATURE_ZILSAXATTR,
 	SPA_FEATURES
 } spa_feature_t;
 

lib/libzfs/libzfs.abi

@@ -347,7 +347,7 @@
     <elf-symbol name='fletcher_4_superscalar4_ops' size='64' type='object-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
     <elf-symbol name='fletcher_4_superscalar_ops' size='64' type='object-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
     <elf-symbol name='libzfs_config_ops' size='16' type='object-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
-    <elf-symbol name='spa_feature_table' size='1904' type='object-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
+    <elf-symbol name='spa_feature_table' size='1960' type='object-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
     <elf-symbol name='zfeature_checks_disable' size='4' type='object-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
     <elf-symbol name='zfs_deleg_perm_tab' size='512' type='object-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
     <elf-symbol name='zfs_history_event_names' size='328' type='object-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
@@ -4396,7 +4396,8 @@
       <enumerator name='SPA_FEATURE_DEVICE_REBUILD' value='31'/>
       <enumerator name='SPA_FEATURE_ZSTD_COMPRESS' value='32'/>
       <enumerator name='SPA_FEATURE_DRAID' value='33'/>
-      <enumerator name='SPA_FEATURES' value='34'/>
+      <enumerator name='SPA_FEATURE_ZILSAXATTR' value='34'/>
+      <enumerator name='SPA_FEATURES' value='35'/>
     </enum-decl>
     <pointer-type-def type-id='type-id-328' size-in-bits='64' id='type-id-329'/>
     <function-decl name='zfeature_lookup_name' visibility='default' binding='global' size-in-bits='64'>
@@ -6712,8 +6713,8 @@
     <pointer-type-def type-id='type-id-463' size-in-bits='64' id='type-id-460'/>
     <typedef-decl name='zfeature_info_t' type-id='type-id-456' id='type-id-464'/>
 
-    <array-type-def dimensions='1' type-id='type-id-464' size-in-bits='15232' id='type-id-465'>
-      <subrange length='34' type-id='type-id-33' id='type-id-395'/>
+    <array-type-def dimensions='1' type-id='type-id-464' size-in-bits='15680' id='type-id-465'>
+      <subrange length='35' type-id='type-id-33' id='type-id-395'/>
 
     </array-type-def>
     <var-decl name='spa_feature_table' type-id='type-id-465' mangled-name='spa_feature_table' visibility='default' elf-symbol-id='spa_feature_table'/>

man/man4/zfs.4

@@ -2073,6 +2073,10 @@ Limit SLOG write size per commit executed with synchronous priority.
 Any writes above that will be executed with lower (asynchronous) priority
 to limit potential SLOG device abuse by single active ZIL writer.
 .
+.It Sy zfs_zil_saxattr_enabled Ns = Ns Sy 1 Pq int
+Enable xattr=sa extended attribute logging in zil.
+Setting value to 0 disables xattr=sa logging in zil.
+.
 .It Sy zfs_embedded_slog_min_ms Ns = Ns Sy 64  Pq int
 Usually, one metaslab from each normal-class vdev is dedicated for use by
 the ZIL to log synchronous writes.

module/os/freebsd/zfs/zfs_vnops_os.c

@@ -5488,7 +5488,7 @@ zfs_deleteextattr_sa(struct vop_deleteextattr_args *ap, const char *attrname)
 	nvl = zp->z_xattr_cached;
 	error = nvlist_remove(nvl, attrname, DATA_TYPE_BYTE_ARRAY);
 	if (error == 0)
-		error = zfs_sa_set_xattr(zp);
+		error = zfs_sa_set_xattr(zp, attrname, NULL, 0);
 	if (error != 0) {
 		zp->z_xattr_cached = NULL;
 		nvlist_free(nvl);
@@ -5624,9 +5624,9 @@ zfs_setextattr_sa(struct vop_setextattr_args *ap, const char *attrname)
 	error = uiomove(buf, entry_size, ap->a_uio);
 	if (error == 0)
 		error = nvlist_add_byte_array(nvl, attrname, buf, entry_size);
-	kmem_free(buf, entry_size);
 	if (error == 0)
-		error = zfs_sa_set_xattr(zp);
+		error = zfs_sa_set_xattr(zp, attrname, buf, entry_size);
+	kmem_free(buf, entry_size);
 	if (error != 0) {
 		zp->z_xattr_cached = NULL;
 		nvlist_free(nvl);

module/os/linux/zfs/zpl_xattr.c

@@ -578,7 +578,7 @@ zpl_xattr_set_sa(struct inode *ip, const char *name, const void *value,
 	 * will be reconstructed from the ARC when next accessed.
 	 */
 	if (error == 0)
-		error = -zfs_sa_set_xattr(zp);
+		error = -zfs_sa_set_xattr(zp, name, value, size);
 
 	if (error) {
 		nvlist_free(nvl);

module/zcommon/zfeature_common.c

@@ -598,6 +598,18 @@ zpool_feature_init(void)
 	zfeature_register(SPA_FEATURE_DRAID,
 	    "org.openzfs:draid", "draid", "Support for distributed spare RAID",
 	    ZFEATURE_FLAG_MOS, ZFEATURE_TYPE_BOOLEAN, NULL);
+
+	{
+	static const spa_feature_t zilsaxattr_deps[] = {
+		SPA_FEATURE_EXTENSIBLE_DATASET,
+		SPA_FEATURE_NONE
+	};
+	zfeature_register(SPA_FEATURE_ZILSAXATTR,
+	    "org.zfsonlinux:zilsaxattr", "zilsaxattr",
+	    "Support for xattr=sa extended attribute logging in zil.",
+	    ZFEATURE_FLAG_READONLY_COMPAT | ZFEATURE_FLAG_ACTIVATE_ON_ENABLE,
+	    ZFEATURE_TYPE_BOOLEAN, zilsaxattr_deps);
+	}
 }
 
 #if defined(_KERNEL)

module/zfs/zfs_log.c

@@ -714,6 +714,40 @@ zfs_log_setattr(zilog_t *zilog, dmu_tx_t *tx, int txtype,
 	zil_itx_assign(zilog, itx, tx);
 }
 
+/*
+ * Handles TX_SETSAXATTR transactions.
+ */
+void
+zfs_log_setsaxattr(zilog_t *zilog, dmu_tx_t *tx, int txtype,
+    znode_t *zp, const char *name, const void *value, size_t size)
+{
+	itx_t		*itx;
+	lr_setsaxattr_t	*lr;
+	size_t		recsize = sizeof (lr_setsaxattr_t);
+	void		*xattrstart;
+	int		namelen;
+
+	if (zil_replaying(zilog, tx) || zp->z_unlinked)
+		return;
+
+	namelen = strlen(name) + 1;
+	recsize += (namelen + size);
+	itx = zil_itx_create(txtype, recsize);
+	lr = (lr_setsaxattr_t *)&itx->itx_lr;
+	lr->lr_foid = zp->z_id;
+	xattrstart = (char *)(lr + 1);
+	bcopy(name, xattrstart, namelen);
+	if (value != NULL) {
+		bcopy(value, (char *)xattrstart + namelen, size);
+		lr->lr_size = size;
+	} else {
+		lr->lr_size = 0;
+	}
+
+	itx->itx_sync = (zp->z_sync_cnt != 0);
+	zil_itx_assign(zilog, itx, tx);
+}
+
 /*
  * Handles TX_ACL transactions.
  */

module/zfs/zfs_replay.c

@@ -47,6 +47,9 @@
 #include <sys/atomic.h>
 #include <sys/cred.h>
 #include <sys/zpl.h>
+#include <sys/dmu.h>
+#include <sys/dmu_objset.h>
+#include <sys/zfeature.h>
 
 /*
  * NB: FreeBSD expects to be able to do vnode locking in lookup and
@@ -868,6 +871,88 @@ zfs_replay_setattr(void *arg1, void *arg2, boolean_t byteswap)
 	return (error);
 }
 
+static int
+zfs_replay_setsaxattr(void *arg1, void *arg2, boolean_t byteswap)
+{
+	zfsvfs_t *zfsvfs = arg1;
+	lr_setsaxattr_t *lr = arg2;
+	znode_t *zp;
+	nvlist_t *nvl;
+	size_t sa_size;
+	char *name;
+	char *value;
+	size_t size;
+	int error = 0;
+
+	ASSERT(spa_feature_is_active(zfsvfs->z_os->os_spa,
+	    SPA_FEATURE_ZILSAXATTR));
+	if (byteswap)
+		byteswap_uint64_array(lr, sizeof (*lr));
+
+	if ((error = zfs_zget(zfsvfs, lr->lr_foid, &zp)) != 0)
+		return (error);
+
+	rw_enter(&zp->z_xattr_lock, RW_WRITER);
+	mutex_enter(&zp->z_lock);
+	if (zp->z_xattr_cached == NULL)
+		error = -zfs_sa_get_xattr(zp);
+	mutex_exit(&zp->z_lock);
+
+	if (error)
+		goto out;
+
+	ASSERT(zp->z_xattr_cached);
+	nvl = zp->z_xattr_cached;
+
+	/* Get xattr name, value and size from log record */
+	size = lr->lr_size;
+	name = (char *)(lr + 1);
+	if (size == 0) {
+		value = NULL;
+		error = -nvlist_remove(nvl, name, DATA_TYPE_BYTE_ARRAY);
+	} else {
+		value = name + strlen(name) + 1;
+		/* Limited to 32k to keep nvpair memory allocations small */
+		if (size > DXATTR_MAX_ENTRY_SIZE) {
+			error = (-EFBIG);
+			goto out;
+		}
+
+		/* Prevent the DXATTR SA from consuming the entire SA region */
+		error = -nvlist_size(nvl, &sa_size, NV_ENCODE_XDR);
+		if (error)
+			goto out;
+
+		if (sa_size > DXATTR_MAX_SA_SIZE) {
+			error = (-EFBIG);
+			goto out;
+		}
+
+		error = -nvlist_add_byte_array(nvl, name, (uchar_t *)value,
+		    size);
+	}
+
+	/*
+	 * Update the SA for additions, modifications, and removals. On
+	 * error drop the inconsistent cached version of the nvlist, it
+	 * will be reconstructed from the ARC when next accessed.
+	 */
+	if (error == 0)
+		error = -zfs_sa_set_xattr(zp, name, value, size);
+
+	if (error) {
+		nvlist_free(nvl);
+		zp->z_xattr_cached = NULL;
+	}
+
+	ASSERT3S(error, <=, 0);
+
+out:
+	rw_exit(&zp->z_xattr_lock);
+	zrele(zp);
+	return (error);
+}
+
 static int
 zfs_replay_acl_v0(void *arg1, void *arg2, boolean_t byteswap)
 {
@@ -989,4 +1074,5 @@ zil_replay_func_t *zfs_replay_vector[TX_MAX_TYPE] = {
 	zfs_replay_create,	/* TX_MKDIR_ATTR */
 	zfs_replay_create_acl,	/* TX_MKDIR_ACL_ATTR */
 	zfs_replay_write2,	/* TX_WRITE2 */
+	zfs_replay_setsaxattr,	/* TX_SETSAXATTR */
 };