ZFS Interface for Accelerators (Z.I.A.)

The ZIO pipeline has been modified to allow for external,
alternative implementations of existing operations to be
used. The original ZFS functions remain in the code as
fallback in case the external implementation fails.

Definitions:
    Accelerator - an entity (usually hardware) that is
                  intended to accelerate operations
    Offloader   - synonym of accelerator; used interchangeably
    Data Processing Unit Services Module (DPUSM)
                - https://github.com/hpc/dpusm
                - defines a "provider API" for accelerator
                  vendors to set up
                - defines a "user API" for accelerator consumers
                  to call
                - maintains list of providers and coordinates
                  interactions between providers and consumers.
    Provider    - a DPUSM wrapper for an accelerator's API
    Offload     - moving data from ZFS/memory to the accelerator
    Onload      - the opposite of offload

In order for Z.I.A. to be extensible, it does not directly
communicate with a fixed accelerator. Rather, Z.I.A. acquires
a handle to a DPUSM, which is then used to acquire handles
to providers.

Using ZFS with Z.I.A.:
    1. Build and start the DPUSM
    2. Implement, build, and register a provider with the DPUSM
    3. Reconfigure ZFS with '--with-zia=<DPUSM root>'
    4. Rebuild and start ZFS
    5. Create a zpool
    6. Select the provider
           zpool set zia_provider=<provider name> <zpool>
    7. Select operations to offload
           zpool set zia_<property>=on <zpool>

The operations that have been modified are:
    - compression
        - non-raw-writes only
    - decompression
    - checksum
        - not handling embedded checksums
        - checksum compute and checksum error call the same function
    - raidz
        - generation
        - reconstruction
    - vdev_file
        - open
        - write
        - close
    - vdev_disk
        - open
        - invalidate
        - write
        - flush
        - close

Successful operations do not bring data back into memory after
they complete, allowing for subsequent offloader operations
reuse the data. This results in only one data movement per ZIO
at the beginning of a pipeline that is necessary for getting
data from ZFS to the accelerator.

When errors ocurr and the offloaded data is still accessible,
the offloaded data will be onloaded (or dropped if it still
matches the in-memory copy) for that ZIO pipeline stage and
processed with ZFS. This will cause thrashing if a later
operation offloads data. This should not happen often, as
constant errors (resulting in data movement) is not expected
to be the norm.

Unrecoverable errors such as hardware failures will trigger
pipeline restarts (if necessary) in order to complete the
original ZIO using the software path.

The modifications to ZFS can be thought of as two sets of changes:
    - The ZIO write pipeline
        - compression, checksum, RAIDZ generation, and write
        - Each stage starts by offloading data that was not
          previously offloaded
            - This allows for ZIOs to be offloaded at any point
              in the pipeline
    - Resilver
        - vdev_raidz_io_done (RAIDZ reconstruction, checksum, and
          RAIDZ generation), and write
        - Because the core of resilver is vdev_raidz_io_done, data
          is only offloaded once at the beginning of
          vdev_raidz_io_done
            - Errors cause data to be onloaded, but will not
              re-offload in subsequent steps within resilver
            - Write is a separate ZIO pipeline stage, so it will
              attempt to offload data

The zio_decompress function has been modified to allow for
offloading but the ZIO read pipeline as a whole has not, so it
is not part of the above list.

An example provider implementation can be found in
module/zia-software-provider
    - The provider's "hardware" is actually software - data is
      "offloaded" to memory not owned by ZFS
    - Calls ZFS functions in order to not reimplement operations
    - Has kernel module parameters that can be used to trigger
      ZIA_ACCELERATOR_DOWN states for testing pipeline restarts.

abd_t, raidz_row_t, and vdev_t have each been given an additional
"void *<prefix>_zia_handle" member. These opaque handles point to
data that is located on an offloader. abds are still allocated,
but their payloads are expected to diverge from the offloaded copy
as operations are run.

Encryption and deduplication are disabled for zpools with Z.I.A.
operations enabled

Aggregation is disabled for offloaded abds

RPMs will build with Z.I.A.

Signed-off-by: Jason Lee <[email protected]>

Makefile.am

@@ -57,6 +57,8 @@ dist_noinst_DATA += module/os/linux/spl/THIRDPARTYLICENSE.gplv2
 dist_noinst_DATA += module/os/linux/spl/THIRDPARTYLICENSE.gplv2.descrip
 dist_noinst_DATA += module/zfs/THIRDPARTYLICENSE.cityhash
 dist_noinst_DATA += module/zfs/THIRDPARTYLICENSE.cityhash.descrip
+dist_noinst_DATA += module/zfs/THIRDPARTYLICENSE.zia
+dist_noinst_DATA += module/zfs/THIRDPARTYLICENSE.zia.descrip
 
 @CODE_COVERAGE_RULES@
 

config/Rules.am

@@ -44,6 +44,7 @@ AM_CPPFLAGS += -DPKGDATADIR=\"$(pkgdatadir)\"
 AM_CPPFLAGS += $(DEBUG_CPPFLAGS)
 AM_CPPFLAGS += $(CODE_COVERAGE_CPPFLAGS)
 AM_CPPFLAGS += -DTEXT_DOMAIN=\"zfs-@ac_system_l@-user\"
+AM_CPPFLAGS += $(ZIA_CPPFLAGS)
 
 if ASAN_ENABLED
 AM_CPPFLAGS += -DZFS_ASAN_ENABLED

config/zfs-build.m4

@@ -263,6 +263,8 @@ AC_DEFUN([ZFS_AC_CONFIG], [
 		AC_SUBST(TEST_JOBS)
 	])
 
+	ZFS_AC_ZIA
+
 	ZFS_INIT_SYSV=
 	ZFS_INIT_SYSTEMD=
 	ZFS_WANT_MODULES_LOAD_D=
@@ -294,7 +296,8 @@ AC_DEFUN([ZFS_AC_CONFIG], [
 	    [test "x$qatsrc" != x ])
 	AM_CONDITIONAL([WANT_DEVNAME2DEVID], [test "x$user_libudev" = xyes ])
 	AM_CONDITIONAL([WANT_MMAP_LIBAIO], [test "x$user_libaio" = xyes ])
-	AM_CONDITIONAL([PAM_ZFS_ENABLED], [test "x$enable_pam" = xyes])
+	AM_CONDITIONAL([PAM_ZFS_ENABLED], [test "x$enable_pam" = xyes ])
+	AM_CONDITIONAL([ZIA_ENABLED], [test "x$enable_zia" = xyes ])
 ])
 
 dnl #
@@ -342,6 +345,10 @@ AC_DEFUN([ZFS_AC_RPM], [
 		RPM_DEFINE_COMMON=${RPM_DEFINE_COMMON}' --define "__strip /bin/true"'
 	])
 
+	AS_IF([test "x$enable_zia" = xyes], [
+		RPM_DEFINE_COMMON=${RPM_DEFINE_COMMON}' --define "$(WITH_ZIA) 1" --define "DPUSM_ROOT $(DPUSM_ROOT)"'
+	])
+
 	RPM_DEFINE_UTIL=' --define "_initconfdir $(initconfdir)"'
 
 	dnl # Make the next three RPM_DEFINE_UTIL additions conditional, since

config/zia.m4

@@ -0,0 +1,45 @@
+dnl # Adds --with-zia=PATH to configuration options
+dnl # The path provided should point to the DPUSM
+dnl # root and contain Module.symvers.
+AC_DEFUN([ZFS_AC_ZIA], [
+	AC_ARG_WITH([zia],
+		AS_HELP_STRING([--with-zia=PATH],
+			[Path to Data Processing Services Module]),
+		[
+			DPUSM_ROOT="$withval"
+			AS_IF([test "x$DPUSM_ROOT" != "xno"],
+				[enable_zia=yes],
+				[enable_zia=no])
+		],
+		[enable_zia=no]
+	)
+
+	AS_IF([test "x$enable_zia" == "xyes"],
+		AS_IF([! test -d "$DPUSM_ROOT"],
+			[AC_MSG_ERROR([--with-zia=PATH requires the DPUSM root directory])]
+		)
+
+		DPUSM_SYMBOLS="$DPUSM_ROOT/Module.symvers"
+
+		AS_IF([test -r $DPUSM_SYMBOLS],
+			[
+				AC_MSG_RESULT([$DPUSM_SYMBOLS])
+				ZIA_CPPFLAGS="-DZIA=1 -I$DPUSM_ROOT/include"
+				KERNEL_ZIA_CPPFLAGS="-DZIA=1 -I$DPUSM_ROOT/include"
+				WITH_ZIA="_with_zia"
+
+				AC_SUBST(WITH_ZIA)
+				AC_SUBST(KERNEL_ZIA_CPPFLAGS)
+				AC_SUBST(ZIA_CPPFLAGS)
+				AC_SUBST(DPUSM_SYMBOLS)
+				AC_SUBST(DPUSM_ROOT)
+			],
+			[
+				AC_MSG_ERROR([
+	*** Failed to find Module.symvers in:
+	$DPUSM_SYMBOLS
+				])
+			]
+		)
+	)
+])

include/Makefile.am

@@ -143,6 +143,9 @@ COMMON_H = \
 	sys/zfs_vfsops.h \
 	sys/zfs_vnops.h \
 	sys/zfs_znode.h \
+	sys/zia.h \
+	sys/zia_cddl.h \
+	sys/zia_private.h \
 	sys/zil.h \
 	sys/zil_impl.h \
 	sys/zio.h \

include/sys/abd.h

@@ -65,6 +65,7 @@ typedef struct abd {
 			list_t abd_gang_chain;
 		} abd_gang;
 	} abd_u;
+	void *abd_zia_handle;
 } abd_t;
 
 typedef int abd_iter_func_t(void *buf, size_t len, void *priv);

include/sys/fs/zfs.h

@@ -265,6 +265,19 @@ typedef enum {
 	ZPOOL_PROP_DEDUP_TABLE_SIZE,
 	ZPOOL_PROP_DEDUP_TABLE_QUOTA,
 	ZPOOL_PROP_DEDUPCACHED,
+	ZPOOL_PROP_ZIA_AVAILABLE,
+	ZPOOL_PROP_ZIA_PROVIDER,
+	ZPOOL_PROP_ZIA_COMPRESS,
+	ZPOOL_PROP_ZIA_DECOMPRESS,
+	ZPOOL_PROP_ZIA_CHECKSUM,
+	ZPOOL_PROP_ZIA_RAIDZ1_GEN,
+	ZPOOL_PROP_ZIA_RAIDZ2_GEN,
+	ZPOOL_PROP_ZIA_RAIDZ3_GEN,
+	ZPOOL_PROP_ZIA_RAIDZ1_REC,
+	ZPOOL_PROP_ZIA_RAIDZ2_REC,
+	ZPOOL_PROP_ZIA_RAIDZ3_REC,
+	ZPOOL_PROP_ZIA_FILE_WRITE,
+	ZPOOL_PROP_ZIA_DISK_WRITE,
 	ZPOOL_NUM_PROPS
 } zpool_prop_t;
 

include/sys/spa_impl.h

@@ -52,6 +52,7 @@
 #include <sys/zfeature.h>
 #include <sys/zthr.h>
 #include <sys/dsl_deadlist.h>
+#include <sys/zia.h>
 #include <zfeature_common.h>
 
 #ifdef	__cplusplus
@@ -479,6 +480,8 @@ struct spa {
 	 */
 	spa_config_lock_t spa_config_lock[SCL_LOCKS]; /* config changes */
 	zfs_refcount_t	spa_refcount;		/* number of opens */
+
+	zia_props_t	spa_zia_props;
 };
 
 extern char *spa_config_path;

include/sys/vdev_disk.h

@@ -42,5 +42,13 @@
 
 #ifdef _KERNEL
 #include <sys/vdev.h>
+
+#ifdef __linux__
+int __vdev_classic_physio(struct block_device *bdev, zio_t *zio,
+    size_t io_size, uint64_t io_offset, int rw, int flags);
+int vdev_disk_io_flush(struct block_device *bdev, zio_t *zio);
+void vdev_disk_error(zio_t *zio);
+#endif /* __linux__ */
+
 #endif /* _KERNEL */
 #endif /* _SYS_VDEV_DISK_H */

include/sys/vdev_file.h

@@ -40,6 +40,10 @@ typedef struct vdev_file {
 extern void vdev_file_init(void);
 extern void vdev_file_fini(void);
 
+#ifdef __linux__
+extern mode_t vdev_file_open_mode(spa_mode_t spa_mode);
+#endif
+
 #ifdef	__cplusplus
 }
 #endif

include/sys/vdev_impl.h

@@ -467,6 +467,8 @@ struct vdev {
 	uint64_t	vdev_io_t;
 	uint64_t	vdev_slow_io_n;
 	uint64_t	vdev_slow_io_t;
+
+	void *vdev_zia_handle;
 };
 
 #define	VDEV_PAD_SIZE		(8 << 10)

include/sys/vdev_raidz.h

@@ -169,6 +169,11 @@ extern int vdev_raidz_load(vdev_t *);
 #define	RAIDZ_EXPAND_PAUSE_SCRATCH_POST_REFLOW_1 6
 #define	RAIDZ_EXPAND_PAUSE_SCRATCH_POST_REFLOW_2 7
 
+void vdev_raidz_generate_parity_p(struct raidz_row *);
+void vdev_raidz_generate_parity_pq(struct raidz_row *);
+void vdev_raidz_generate_parity_pqr(struct raidz_row *);
+void vdev_raidz_reconstruct_general(struct raidz_row *, int *, int);
+
 #ifdef	__cplusplus
 }
 #endif

include/sys/vdev_raidz_impl.h

@@ -136,6 +136,7 @@ typedef struct raidz_row {
 	uint64_t rr_offset;		/* Logical offset for *_io_verify() */
 	uint64_t rr_size;		/* Physical size for *_io_verify() */
 #endif
+	void *rr_zia_handle;
 	raidz_col_t rr_col[];		/* Flexible array of I/O columns */
 } raidz_row_t;
 

include/sys/zap_impl.h

@@ -61,7 +61,7 @@ typedef struct mzap_phys {
 	uint64_t mz_salt;
 	uint64_t mz_normflags;
 	uint64_t mz_pad[5];
-	mzap_ent_phys_t mz_chunk[1];
+	mzap_ent_phys_t mz_chunk[];
 	/* actually variable size depending on block size */
 } mzap_phys_t;