Implement physical rewrites

Based on previous commit this implements `zfs rewrite -P` flag,
making ZFS to keep blocks logical birth times while rewriting
files.  It should exclude the rewritten blocks from incremental
sends, snapshot diffs, etc.  Snapshots space usage same time will
reflect the additional space usage from newly allocated blocks.

Since this begins to use new "rewrite" flag in the block pointers,
this commit introduces a new read-compatible per-dataset feature
physical_rewrite.  It must be enabled for the command to not fail,
it is activated on first use and deactivated on deletion of the
last affected dataset.

Reviewed-by: Rob Norris <robn@despairlabs.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by:  Alexander Motin <alexander.motin@TrueNAS.com>
Closes #17565

include/sys/dbuf.h

@@ -164,6 +164,7 @@ typedef struct dbuf_dirty_record {
 			boolean_t dr_nopwrite;
 			boolean_t dr_brtwrite;
 			boolean_t dr_diowrite;
+			boolean_t dr_rewrite;
 			boolean_t dr_has_raw_params;
 
 			/* Override and raw params are mutually exclusive. */

include/sys/dmu.h

@@ -825,6 +825,7 @@ struct blkptr *dmu_buf_get_blkptr(dmu_buf_t *db);
  */
 void dmu_buf_will_dirty(dmu_buf_t *db, dmu_tx_t *tx);
 void dmu_buf_will_dirty_flags(dmu_buf_t *db, dmu_tx_t *tx, dmu_flags_t flags);
+void dmu_buf_will_rewrite(dmu_buf_t *db, dmu_tx_t *tx);
 boolean_t dmu_buf_is_dirty(dmu_buf_t *db, dmu_tx_t *tx);
 void dmu_buf_set_crypt_params(dmu_buf_t *db_fake, boolean_t byteorder,
     const uint8_t *salt, const uint8_t *iv, const uint8_t *mac, dmu_tx_t *tx);

include/sys/fs/zfs.h

@@ -1627,6 +1627,9 @@ typedef struct zfs_rewrite_args {
 	uint64_t	arg;
 } zfs_rewrite_args_t;
 
+/* zfs_rewrite_args flags */
+#define	ZFS_REWRITE_PHYSICAL	0x1	/* Preserve logical birth time. */
+
 #define	ZFS_IOC_REWRITE		_IOW(0x83, 3, zfs_rewrite_args_t)
 
 /*

include/sys/zio.h

@@ -374,6 +374,7 @@ typedef struct zio_prop {
 	boolean_t		zp_encrypt;
 	boolean_t		zp_byteorder;
 	boolean_t		zp_direct_write;
+	boolean_t		zp_rewrite;
 	uint8_t			zp_salt[ZIO_DATA_SALT_LEN];
 	uint8_t			zp_iv[ZIO_DATA_IV_LEN];
 	uint8_t			zp_mac[ZIO_DATA_MAC_LEN];

include/zfeature_common.h

@@ -89,6 +89,7 @@ typedef enum spa_feature {
 	SPA_FEATURE_LARGE_MICROZAP,
 	SPA_FEATURE_DYNAMIC_GANG_HEADER,
 	SPA_FEATURE_BLOCK_CLONING_ENDIAN,
+	SPA_FEATURE_PHYSICAL_REWRITE,
 	SPA_FEATURES
 } spa_feature_t;