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* [PATCH v3 0/2] btrfs-progs: receive: introduce new --clone-fallback option
@ 2021-10-05  1:14 Qu Wenruo
  2021-10-05  1:14 ` [PATCH v3 1/2] btrfs-progs: receive: fallback to buffered copy if clone failed Qu Wenruo
  2021-10-05  1:14 ` [PATCH v3 2/2] btrfs-progs: misc-tests: add test case for receive --clone-fallback Qu Wenruo
  0 siblings, 2 replies; 3+ messages in thread
From: Qu Wenruo @ 2021-10-05  1:14 UTC (permalink / raw)
  To: linux-btrfs

When parent stream and incremental stream are received with different
nodatasum mount options, any clone opeartion in the incremental stream
will be rejected by kernel.

There are more situations to cause clone failure, like receiving a stream
on a fs with different sectorsize.

Thus this patchset will introduce a new option, --clone-fallback, for
btrfs receive to fall back to buffered write when clone failed.

This fall back behavior will only happen if the new option is explicitly
specified, as such behavior can hide some send bugs, and under most sane
cases users don't need such option.

Also add a test case for the new option.

Changelog:
RFC->v1:
- Introduce a new option for the fallback behavior
  To avoid hide send bugs.

- Hide the warning message behind -v option
  Since we have a special option for it thus users are aware of what
  they are doing, there is no need to output such warning by default.

- Add a new test case for it

v2:
- Add the missing help string for --clone-fallback option

- Rephrase the words in comments and commit messages

- Add run_check_remount_test_dev() helper

v3:
- Add an overview of failed clone operations for --clone-fallback option

- Update doc words again

Qu Wenruo (2):
  btrfs-progs: receive: fallback to buffered copy if clone failed
  btrfs-progs: misc-tests: add test case for receive --clone-fallback

 Documentation/btrfs-receive.asciidoc          | 13 +++
 cmds/receive.c                                | 80 ++++++++++++++++++-
 tests/common                                  |  9 +++
 .../049-receive-clone-fallback/test.sh        | 58 ++++++++++++++
 4 files changed, 157 insertions(+), 3 deletions(-)
 create mode 100755 tests/misc-tests/049-receive-clone-fallback/test.sh

-- 
2.33.0


^ permalink raw reply	[flat|nested] 3+ messages in thread

* [PATCH v3 1/2] btrfs-progs: receive: fallback to buffered copy if clone failed
  2021-10-05  1:14 [PATCH v3 0/2] btrfs-progs: receive: introduce new --clone-fallback option Qu Wenruo
@ 2021-10-05  1:14 ` Qu Wenruo
  2021-10-05  1:14 ` [PATCH v3 2/2] btrfs-progs: misc-tests: add test case for receive --clone-fallback Qu Wenruo
  1 sibling, 0 replies; 3+ messages in thread
From: Qu Wenruo @ 2021-10-05  1:14 UTC (permalink / raw)
  To: linux-btrfs; +Cc: Filipe Manana

[BUG]
There are two very basic send streams:
(a/m/ctime and uuid omitted)

  Stream 1: (Parent subvolume)
  subvol   ./parent_subv           transid=8
  chown    ./parent_subv/          gid=0 uid=0
  chmod    ./parent_subv/          mode=755
  utimes   ./parent_subv/
  mkfile   ./parent_subv/o257-7-0
  rename   ./parent_subv/o257-7-0  dest=./parent_subv/source
  utimes   ./parent_subv/
  write    ./parent_subv/source    offset=0 len=16384
  chown    ./parent_subv/source    gid=0 uid=0
  chmod    ./parent_subv/source    mode=600
  utimes   ./parent_subv/source

  Stream 2: (snapshot and clone)
  snapshot ./dest_subv             transid=14 parent_transid=10
  utimes   ./dest_subv/
  mkfile   ./dest_subv/o258-14-0
  rename   ./dest_subv/o258-14-0   dest=./dest_subv/reflink
  utimes   ./dest_subv/
  clone    ./dest_subv/reflink     offset=0 len=16384 from=./dest_subv/source clone_offset=0
  chown    ./dest_subv/reflink     gid=0 uid=0
  chmod    ./dest_subv/reflink     mode=600
  utimes   ./dest_subv/reflink

But if we receive the first stream with default mount, then remount to
nodatasum, and try to receive the second stream, it will fail:

 # mount /mnt/btrfs
 # btrfs receive -f ~/parent_stream /mnt/btrfs/
 At subvol parent_subv
 # mount -o remount,nodatasum /mnt/btrfs
 # btrfs receive -f ~/clone_stream /mnt/btrfs/
 At snapshot dest_subv
 ERROR: failed to clone extents to reflink: Invalid argument
 # echo $?
 1

[CAUSE]
Btrfs doesn't allow clone source and destination files have different
NODATASUM flags.
This is to prevent a data extent to be owned by both NODATASUM inode and
regular DATASUM inode.

For above receive operations, the clone destination is inheriting the
NODATASUM flag from mount option, while the clone source has no
NODATASUM flag, thus preventing us from doing the clone.

[FIX]
Btrfs send/receive doesn't require the underlying inode has the same
flags (thus we can send from compressed extent and receive on a
non-compressed filesystem).

So here we add a new command line option, '--clone-fallback', to allow
btrfs-receive to fall back to buffered write to copy data from the
source file.

Since such behavior can result much less clone operations, which may not
be what the end users really want, and can hide bugs in send stream.
Thus this behavior must be explicitly specified by the new option.

And we will output a warning message each time such fallback is
triggered if the user wants extra debug output.

Finally if we have any failed clone operation when --clone-fallback is
specified, also output a overview at the end of the received process,
showing how many clone opeartions failed and how many bytes are no
longer shared.

Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 Documentation/btrfs-receive.asciidoc | 13 +++++
 cmds/receive.c                       | 80 ++++++++++++++++++++++++++--
 2 files changed, 90 insertions(+), 3 deletions(-)

diff --git a/Documentation/btrfs-receive.asciidoc b/Documentation/btrfs-receive.asciidoc
index e4c4d2c0bf3d..adf73c9cedae 100644
--- a/Documentation/btrfs-receive.asciidoc
+++ b/Documentation/btrfs-receive.asciidoc
@@ -65,6 +65,19 @@ dump the stream metadata, one line per operation
 +
 Does not require the 'path' parameter. The filesystem remains unchanged.
 
+--clone-fallback::
+when clone operations fail, attempt to directly copy the data instead.
++
+When the source and destination filesystems have different sector sizes, or
+when the source and destination files have different 'nodatacow' and/or
+'nodatasum' flags (can be set per file/directory or through mount options),
+clone operations can fail.
++
+This option makes the receive process attempt to manually copy data from the
+source to the destination file when a clone operation fails (for the reasons
+mentioned before). When this happens, extents will end up not being shared
+between the files, thus will take up more space.
+
 -q|--quiet::
 (deprecated) alias for global '-q' option
 
diff --git a/cmds/receive.c b/cmds/receive.c
index 48c774cea587..20deccfdf1b2 100644
--- a/cmds/receive.c
+++ b/cmds/receive.c
@@ -76,6 +76,15 @@ struct btrfs_receive
 	struct subvol_uuid_search sus;
 
 	int honor_end_cmd;
+
+	bool clone_fallback;
+
+	/*
+	 * The amount of failed clone opeartions and their bytes.
+	 * Will only be non-zero if above clone_fallback is true.
+	 */
+	u64 bytes_clone_failed;
+	u64 nr_clone_failed;
 };
 
 static int finish_subvol(struct btrfs_receive *rctx)
@@ -705,6 +714,44 @@ out:
 	return ret;
 }
 
+static int buffered_copy(int src_fd, int dst_fd, u64 src_offset, u64 len,
+			 u64 dest_offset)
+{
+	unsigned char buf[SZ_32K];
+	u64 copied = 0;
+	int ret = 0;
+
+	while (copied < len) {
+		u32 copy_len = min_t(u32, ARRAY_SIZE(buf), len - copied);
+		u32 written = 0;
+		ssize_t read_size;
+
+		read_size = pread(src_fd, buf, copy_len, src_offset + copied);
+		if (read < 0) {
+			ret = -errno;
+			error("failed to read source file: %m");
+			return ret;
+		}
+
+		/* Write the buffer to dest file */
+		while (written < read_size) {
+			ssize_t write_size;
+
+			write_size = pwrite(dst_fd, buf + written,
+					read_size - written,
+					dest_offset + copied + written);
+			if (write_size < 0) {
+				ret = -errno;
+				error("failed to write source file: %m");
+				return ret;
+			}
+			written += write_size;
+		}
+		copied += read_size;
+	}
+	return ret;
+}
+
 static int process_clone(const char *path, u64 offset, u64 len,
 			 const u8 *clone_uuid, u64 clone_ctransid,
 			 const char *clone_path, u64 clone_offset,
@@ -788,8 +835,24 @@ static int process_clone(const char *path, u64 offset, u64 len,
 	ret = ioctl(rctx->write_fd, BTRFS_IOC_CLONE_RANGE, &clone_args);
 	if (ret < 0) {
 		ret = -errno;
-		error("failed to clone extents to %s: %m", path);
-		goto out;
+		if (ret != -EINVAL || !rctx->clone_fallback) {
+			error(
+"clone failed, source=%s source offset=%llu destination=%s destination offset=%llu len=%llu: %m",
+			      full_clone_path, clone_offset, path, offset, len);
+			goto out;
+		}
+
+		/*
+		 * Here we don't need extra info about the failed clone
+		 * operation, as for verbose >= 2 such info is already there,
+		 * just one line before.
+		 */
+		if (bconf.verbose >= 2)
+			warning("clone failed, fallback to buffered write");
+		rctx->bytes_clone_failed += len;
+		rctx->nr_clone_failed++;
+		ret = buffered_copy(clone_fd, rctx->write_fd, clone_offset,
+				    len, offset);
 	}
 
 out:
@@ -1165,6 +1228,10 @@ out:
 		close(rctx->dest_dir_fd);
 		rctx->dest_dir_fd = -1;
 	}
+	if (rctx->clone_fallback && rctx->bytes_clone_failed)
+		warning(
+	"%llu clone operations failed, %llu bytes fell back to buffered write",
+			rctx->nr_clone_failed, rctx->bytes_clone_failed);
 
 	return ret;
 }
@@ -1197,6 +1264,8 @@ static const char * const cmd_receive_usage[] = {
 	"                 this file system is mounted.",
 	"--dump           dump stream metadata, one line per operation,",
 	"                 does not require the MOUNT parameter",
+	"--clone-fallback when clone operations fail, attempt to directly copy"
+	"                 the data instead"
 	"-v               deprecated, alias for global -v option",
 	HELPINFO_INSERT_GLOBALS,
 	HELPINFO_INSERT_VERBOSE,
@@ -1238,11 +1307,13 @@ static int cmd_receive(const struct cmd_struct *cmd, int argc, char **argv)
 	optind = 0;
 	while (1) {
 		int c;
-		enum { GETOPT_VAL_DUMP = 257 };
+		enum { GETOPT_VAL_DUMP = 257, GETOPT_VAL_CLONE_FALLBACK };
 		static const struct option long_opts[] = {
 			{ "max-errors", required_argument, NULL, 'E' },
 			{ "chroot", no_argument, NULL, 'C' },
 			{ "dump", no_argument, NULL, GETOPT_VAL_DUMP },
+			{ "clone-fallback", no_argument, NULL,
+				GETOPT_VAL_CLONE_FALLBACK},
 			{ "quiet", no_argument, NULL, 'q' },
 			{ NULL, 0, NULL, 0 }
 		};
@@ -1286,6 +1357,9 @@ static int cmd_receive(const struct cmd_struct *cmd, int argc, char **argv)
 		case GETOPT_VAL_DUMP:
 			dump = 1;
 			break;
+		case GETOPT_VAL_CLONE_FALLBACK:
+			rctx.clone_fallback = true;
+			break;
 		default:
 			usage_unknown_option(cmd, argv);
 		}
-- 
2.33.0


^ permalink raw reply related	[flat|nested] 3+ messages in thread

* [PATCH v3 2/2] btrfs-progs: misc-tests: add test case for receive --clone-fallback
  2021-10-05  1:14 [PATCH v3 0/2] btrfs-progs: receive: introduce new --clone-fallback option Qu Wenruo
  2021-10-05  1:14 ` [PATCH v3 1/2] btrfs-progs: receive: fallback to buffered copy if clone failed Qu Wenruo
@ 2021-10-05  1:14 ` Qu Wenruo
  1 sibling, 0 replies; 3+ messages in thread
From: Qu Wenruo @ 2021-10-05  1:14 UTC (permalink / raw)
  To: linux-btrfs; +Cc: Filipe Manana

The new test case will create two send streams:

- parent_stream
  A full send stream.
  Contains one file, as clone source.

- clone_stream
  An incremental send stream.
  Contains one clone operation.

Then we will receive the parent_stream with default mount options, while
try to receive the clone_stream with nodatasum mount option.

This should result clone failure due to nodatasum flag mismatch.

Then check if the receive can continue with --clone-fallback option.

Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 tests/common                                  |  9 +++
 .../049-receive-clone-fallback/test.sh        | 58 +++++++++++++++++++
 2 files changed, 67 insertions(+)
 create mode 100755 tests/misc-tests/049-receive-clone-fallback/test.sh

diff --git a/tests/common b/tests/common
index 253071025db2..0423af4231a8 100644
--- a/tests/common
+++ b/tests/common
@@ -633,6 +633,15 @@ run_check_mount_test_dev()
 	run_check $SUDO_HELPER mount -t btrfs $loop_opt "$@" "$TEST_DEV" "$TEST_MNT"
 }
 
+run_check_remount_test_dev()
+{
+	setup_root_helper
+
+	local opts="$1"
+
+	run_check $SUDO_HELPER mount -o "remount,$opts" "$TEST_MNT"
+}
+
 # $1-$n: optional paths to unmount, otherwise fallback to TEST_DEV
 run_check_umount_test_dev()
 {
diff --git a/tests/misc-tests/049-receive-clone-fallback/test.sh b/tests/misc-tests/049-receive-clone-fallback/test.sh
new file mode 100755
index 000000000000..18136a9e63ee
--- /dev/null
+++ b/tests/misc-tests/049-receive-clone-fallback/test.sh
@@ -0,0 +1,58 @@
+#!/bin/bash
+# Verify that btrfs receive can fallback to buffered copy when clone
+# failed
+
+source "$TEST_TOP/common"
+
+check_prereq mkfs.btrfs
+check_prereq btrfs
+setup_root_helper
+prepare_test_dev
+
+tmp=$(mktemp -d --tmpdir btrfs-progs-send-stream.XXXXXX)
+
+# Create two sends stream, one as the parent and the other as an incremental
+# stream with one clone operation.
+run_check_mkfs_test_dev
+run_check_mount_test_dev -o datacow,datasum
+run_check $SUDO_HELPER "$TOP/btrfs" subvolume create "$TEST_MNT/subv"
+run_check $SUDO_HELPER dd if=/dev/zero bs=1M count=1 of="$TEST_MNT/subv/file1" 
+run_check $SUDO_HELPER "$TOP/btrfs" subvolume snapshot -r "$TEST_MNT/subv" \
+	"$TEST_MNT/snap1"
+run_check $SUDO_HELPER cp --reflink=always "$TEST_MNT/subv/file1" \
+	"$TEST_MNT/subv/file2"
+run_check $SUDO_HELPER "$TOP/btrfs" subvolume snapshot -r "$TEST_MNT/subv" \
+	"$TEST_MNT/snap2"
+
+run_check $SUDO_HELPER "$TOP/btrfs" send -f "$tmp/parent_stream" \
+	"$TEST_MNT/snap1"
+run_check $SUDO_HELPER "$TOP/btrfs" send -f "$tmp/clone_stream" \
+	-p "$TEST_MNT/snap1" "$TEST_MNT/snap2"
+
+run_check_umount_test_dev
+run_check_mkfs_test_dev
+
+# Receive the first stream with the same mount option
+run_check_mount_test_dev -o datacow -o datasum
+
+# Receiving the full stream should not fail
+run_check $SUDO_HELPER "$TOP/btrfs" receive -f "$tmp/parent_stream" "$TEST_MNT"
+
+# Remount the fs with nodatasum mount option, so that the new file received
+# through the incremental stream will end up with the nodatasum flag set.
+run_check_remount_test_dev nodatasum
+
+# Receiving incremental send stream without --clone-fallback should fail.
+# As the clone source and destination have different NODATASUM flags
+run_mustfail "receiving clone with different NODATASUM should fail" \
+	$SUDO_HELPER "$TOP/btrfs" receive -f "$tmp/clone_stream" "$TEST_MNT"
+
+# Firstly we need to cleanup the partially received subvolume
+run_check $SUDO_HELPER "$TOP/btrfs" subvolume delete "$TEST_MNT/snap2"
+
+# With --clone-fallback specified, the receive should finish without problem
+run_check $SUDO_HELPER "$TOP/btrfs" receive --clone-fallback \
+	-f "$tmp/clone_stream" "$TEST_MNT"
+run_check_umount_test_dev
+
+rm -rf -- "$tmp"
-- 
2.33.0


^ permalink raw reply related	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2021-10-05  1:15 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-10-05  1:14 [PATCH v3 0/2] btrfs-progs: receive: introduce new --clone-fallback option Qu Wenruo
2021-10-05  1:14 ` [PATCH v3 1/2] btrfs-progs: receive: fallback to buffered copy if clone failed Qu Wenruo
2021-10-05  1:14 ` [PATCH v3 2/2] btrfs-progs: misc-tests: add test case for receive --clone-fallback Qu Wenruo

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