Implement Redacted Send/Receive

Redacted send/receive allows users to send subsets of their data to 
a target system. One possible use case for this feature is to not 
transmit sensitive information to a data warehousing, test/dev, or 
analytics environment. Another is to save space by not replicating 
unimportant data within a given dataset, for example in backup tools 
like zrepl.

Redacted send/receive is a three-stage process. First, a clone (or 
clones) is made of the snapshot to be sent to the target. In this 
clone (or clones), all unnecessary or unwanted data is removed or
modified. This clone is then snapshotted to create the "redaction 
snapshot" (or snapshots). Second, the new zfs redact command is used 
to create a redaction bookmark. The redaction bookmark stores the 
list of blocks in a snapshot that were modified by the redaction 
snapshot(s). Finally, the redaction bookmark is passed as a parameter 
to zfs send. When sending to the snapshot that was redacted, the
redaction bookmark is used to filter out blocks that contain sensitive 
or unwanted information, and those blocks are not included in the send 
stream.  When sending from the redaction bookmark, the blocks it 
contains are considered as candidate blocks in addition to those 
blocks in the destination snapshot that were modified since the 
creation_txg of the redaction bookmark.  This step is necessary to 
allow the target to rehydrate data in the case where some blocks are 
accidentally or unnecessarily modified in the redaction snapshot.

The changes to bookmarks to enable fast space estimation involve 
adding deadlists to bookmarks. There is also logic to manage the 
life cycles of these deadlists.

The new size estimation process operates in cases where previously 
an accurate estimate could not be provided. In those cases, a send 
is performed where no data blocks are read, reducing the runtime 
significantly and providing a byte-accurate size estimate.

Reviewed-by: Dan Kimmel <dan.kimmel@delphix.com>
Reviewed-by: Matt Ahrens <mahrens@delphix.com>
Reviewed-by: Prashanth Sreenivasa <pks@delphix.com>
Reviewed-by: John Kennedy <john.kennedy@delphix.com>
Reviewed-by: George Wilson <george.wilson@delphix.com>
Reviewed-by: Chris Williamson <chris.williamson@delphix.com>
Reviewed-by: Pavel Zhakarov <pavel.zakharov@delphix.com>
Reviewed-by: Sebastien Roy <sebastien.roy@delphix.com>
Reviewed-by: Prakash Surya <prakash.surya@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Paul Dagnelie <pcd@delphix.com>
Closes #7958

man/man8/zfs.8

@@ -177,7 +177,7 @@
 .Cm mount
 .Nm
 .Cm mount
-.Op Fl Olv
+.Op Fl Oflv
 .Op Fl o Ar options
 .Fl a | Ar filesystem
 .Nm
@@ -200,11 +200,18 @@
 .Ar snapshot
 .Nm
 .Cm send
-.Op Fl LPcenvw
-.Op Fl i Ar snapshot Ns | Ns Ar bookmark
+.Op Fl DLPcenpvw
+.Oo Fl i Ar snapshot Ns | Ns Ar bookmark
+.Oc
 .Ar filesystem Ns | Ns Ar volume Ns | Ns Ar snapshot
 .Nm
 .Cm send
+.Fl -redact Ar redaction_bookmark
+.Op Fl DLPcenpv
+.Op Fl i Ar snapshot Ns | Ns Ar bookmark
+.Ar snapshot
+.Nm
+.Cm send
 .Op Fl Penv
 .Fl t Ar receive_resume_token
 .Nm
@@ -227,6 +234,10 @@
 .Fl A
 .Ar filesystem Ns | Ns Ar volume
 .Nm
+.Cm redact
+.Ar snapshot redaction_bookmark
+.Op Ar redaction_snapshot Ns ...
+.Nm
 .Cm allow
 .Ar filesystem Ns | Ns Ar volume
 .Nm
@@ -740,6 +751,11 @@ this opaque token can be provided to
 .Sy zfs send -t
 to resume and complete the
 .Sy zfs receive .
+.It Sy redact_snaps
+For bookmarks, this is the list of snapshot guids the bookmark contains a redaction
+list for.
+For snapshots, this is the list of snapshot guids the snapshot is redacted with
+respect to.
 .It Sy referenced
 The amount of data that is accessible by this dataset, which may or may not be
 shared with other datasets in the pool.
@@ -2454,6 +2470,76 @@ would normally be. Since compression is applied before encryption datasets may
 be vulnerable to a CRIME-like attack if applications accessing the data allow
 for it. Deduplication with encryption will leak information about which blocks
 are equivalent in a dataset and will incur an extra CPU cost per block written.
+.Ss Redaction
+ZFS has support for a limited version of data subsetting, in the form of
+redaction. Using the
+.Sy zfs redact
+command, a
+.Sy redaction bookmark
+can be created that stores a list of blocks containing sensitive information. When
+provided to
+.Sy zfs
+.Sy send ,
+this causes a
+.Sy redacted send
+to occur. Redacted sends omit the blocks containing sensitive information,
+replacing them with REDACT records. When these send streams are received, a
+.Sy redacted dataset
+is created. A redacted dataset cannot be mounted by default, since it is
+incomplete. It can be used to receive other send streams. In this way datasets
+can be used for data backup and replication, with all the benefits that zfs send
+and receive have to offer, while protecting sensitive information from being
+stored on less-trusted machines or services.
+.Pp
+For the purposes of redaction, there are two steps to the process. A redact
+step, and a send/receive step. First, a redaction bookmark is created. This is
+done by providing the
+.Sy zfs redact
+command with a parent snapshot, a bookmark to be created, and a number of
+redaction snapshots. These redaction snapshots must be descendants of the
+parent snapshot, and they should modify data that is considered sensitive in
+some way. Any blocks of data modified by all of the redaction snapshots will
+be listed in the redaction bookmark, because it represents the truly sensitive
+information. When it comes to the send step, the send process will not send
+the blocks listed in the redaction bookmark, instead replacing them with
+REDACT records. When received on the target system, this will create a
+redacted dataset, missing the data that corresponds to the blocks in the
+redaction bookmark on the sending system. The incremental send streams from
+the original parent to the redaction snapshots can then also be received on
+the target system, and this will produce a complete snapshot that can be used
+normally. Incrementals from one snapshot on the parent filesystem and another
+can also be done by sending from the redaction bookmark, rather than the
+snapshots themselves.
+.Pp
+In order to make the purpose of the feature more clear, an example is
+provided. Consider a zfs filesystem containing four files. These files
+represent information for an online shopping service. One file contains a list
+of usernames and passwords, another contains purchase histories, a third
+contains click tracking data, and a fourth contains user preferences.  The
+owner of this data wants to make it available for their development teams to
+test against, and their market research teams to do analysis on.  The
+development teams need information about user preferences and the click
+tracking data, while the market research teams need information about purchase
+histories and user preferences. Neither needs access to the usernames and
+passwords. However, because all of this data is stored in one ZFS filesystem,
+it must all be sent and received together. In addition, the owner of the data
+wants to take advantage of features like compression, checksumming, and
+snapshots, so they do want to continue to use ZFS to store and transmit their
+data.  Redaction can help them do so. First, they would make two clones of a
+snapshot of the data on the source. In one clone, they create the setup they
+want their market research team to see; they delete the usernames and
+passwords file, and overwrite the click tracking data with dummy
+information. In another, they create the setup they want the development teams
+to see, by replacing the passwords with fake information and replacing the
+purchase histories with randomly generated ones.  They would then create a
+redaction bookmark on the parent snapshot, using snapshots on the two clones
+as redaction snapshots. The parent can then be sent, redacted, to the target
+server where the research and development teams have access. Finally,
+incremental sends from the parent snapshot to each of the clones can be send
+to and received on the target server; these snapshots are identical to the
+ones on the source, and are ready to be used, while the parent snapshot on the
+target contains none of the username and password data present on the source,
+because it was removed by the redacted send operation.
 .Sh SUBCOMMANDS
 All subcommands that modify state are logged persistently to the pool in their
 original form.
@@ -3329,7 +3415,7 @@ Displays all ZFS file systems currently mounted.
 .It Xo
 .Nm
 .Cm mount
-.Op Fl Olv
+.Op Fl Oflv
 .Op Fl o Ar options
 .Fl a | Ar filesystem
 .Xc
@@ -3370,6 +3456,8 @@ of
 this will cause the terminal to interactively block after asking for the key.
 .It Fl v
 Report mount progress.
+.It Fl f
+Attempt to force mounting of all filesystems, even those that couldn't normally be mounted (e.g. redacted datasets).
 .El
 .It Xo
 .Nm
@@ -3650,7 +3738,7 @@ You will be able to receive your streams on future versions of ZFS.
 .It Xo
 .Nm
 .Cm send
-.Op Fl LPcenvw
+.Op Fl DLPRcenpvw
 .Op Fl i Ar snapshot Ns | Ns Ar bookmark
 .Ar filesystem Ns | Ns Ar volume Ns | Ns Ar snapshot
 .Xc
@@ -3775,6 +3863,97 @@ This information includes a per-second report of how much data has been sent.
 .It Xo
 .Nm
 .Cm send
+.Fl -redact Ar redaction_bookmark
+.Op Fl DLPcenpv
+.br
+.Op Fl i Ar snapshot Ns | Ns Ar bookmark
+.Ar snapshot
+.Xc
+Generate a redacted send stream.
+This send stream contains all blocks from the snapshot being sent that aren't
+included in the redaction list contained in the bookmark specified by the
+.Fl -redact
+(or
+.Fl -d
+) flag.
+The resulting send stream is said to be redacted with respect to the snapshots
+the bookmark specified by the
+.Fl -redact No flag was created with.
+The bookmark must have been created by running
+.Sy zfs redact
+on the snapshot being sent.
+.sp
+This feature can be used to allow clones of a filesystem to be made available on
+a remote system, in the case where their parent need not (or needs to not) be
+usable.
+For example, if a filesystem contains sensitive data, and it has clones where
+that sensitive data has been secured or replaced with dummy data, redacted sends
+can be used to replicate the secured data without replicating the original
+sensitive data, while still sharing all possible blocks.
+A snapshot that has been redacted with respect to a set of snapshots will
+contain all blocks referenced by at least one snapshot in the set, but will
+contain none of the blocks referenced by none of the snapshots in the set.
+In other words, if all snapshots in the set have modified a given block in the
+parent, that block will not be sent; but if one or more snapshots have not
+modified a block in the parent, they will still reference the parent's block, so
+that block will be sent.
+Note that only user data will be redacted.
+.sp
+When the redacted send stream is received, we will generate a redacted
+snapshot.
+Due to the nature of redaction, a redacted dataset can only be used in the
+following ways:
+.sp
+1. To receive, as a clone, an incremental send from the original snapshot to one
+of the snapshots it was redacted with respect to.
+In this case, the stream will produce a valid dataset when received because all
+blocks that were redacted in the parent are guaranteed to be present in the
+child's send stream.
+This use case will produce a normal snapshot, which can be used just like other
+snapshots.
+.sp
+2. To receive an incremental send from the original snapshot to something
+redacted with respect to a subset of the set of snapshots the initial snapshot
+was redacted with respect to.
+In this case, each block that was redacted in the original is still redacted
+(redacting with respect to additional snapshots causes less data to be redacted
+(because the snapshots define what is permitted, and everything else is
+redacted)).
+This use case will produce a new redacted snapshot.
+.sp
+3. To receive an incremental send from a redaction bookmark of the original
+snapshot that was created when redacting with respect to a subset of the set of
+snapshots the initial snapshot was created with respect to
+anything else.
+A send stream from such a redaction bookmark will contain all of the blocks
+necessary to fill in any redacted data, should it be needed, because the sending
+system is aware of what blocks were originally redacted.
+This will either produce a normal snapshot or a redacted one, depending on
+whether the new send stream is redacted.
+.sp
+4. To receive an incremental send from a redacted version of the initial
+snapshot that is redacted with respect to a subect of the set of snapshots the
+initial snapshot was created with respect to.
+A send stream from a compatible redacted dataset will contain all of the blocks
+necessary to fill in any redacted data.
+This will either produce a normal snapshot or a redacted one, depending on
+whether the new send stream is redacted.
+.sp
+5. To receive a full send as a clone of the redacted snapshot.
+Since the stream is a full send, it definitionally contains all the data needed
+to create a new dataset.
+This use case will either produce a normal snapshot or a redacted one, depending
+on whether the full send stream was redacted.
+.sp
+These restrictions are detected and enforced by \fBzfs receive\fR; a
+redacted send stream will contain the list of snapshots that the stream is
+redacted with respsect to.
+These are stored with the redacted snapshot, and are used to detect and
+correctly handle the cases above.  Note that for technical reasons, raw sends
+and redacted sends cannot be combined at this time.
+.It Xo
+.Nm
+.Cm send
 .Op Fl Penv
 .Fl t
 .Ar receive_resume_token
@@ -4091,6 +4270,24 @@ Abort an interrupted
 deleting its saved partially received state.
 .It Xo
 .Nm
+.Cm redact
+.Ar snapshot redaction_bookmark
+.Op Ar redaction_snapshot Ns ...
+.Xc
+Generate a new redaction bookmark.
+In addition to the typical bookmark information, a redaction bookmark contains
+the list of redacted blocks and the list of redaction snapshots specified.
+The redacted blocks are blocks in the snapshot which are not referenced by any
+of the redaction snapshots.
+These blocks are found by iterating over the metadata in each redaction snapshot
+to determine what has been changed since the target snapshot.
+Redaction is designed to support redacted zfs sends; see the entry for
+.Sy zfs send
+for more information on the purpose of this operation.
+If a redact operation fails partway through (due to an error or a system
+failure), the redaction can be resumed by rerunning the same command.
+.It Xo
+.Nm
 .Cm allow
 .Ar filesystem Ns | Ns Ar volume
 .Xc