[PATCHSET 0/3] fstests: fix tests when XFS always_cow mode enabled

[PATCHSET 0/3] fstests: fix tests when XFS always_cow mode enabled

[Darrick J. Wong]

Hi all,

This patchset adjust various adjustments or _notruns that need to happen
when always_cow mode is enabled in XFS.

If you're going to start using this mess, you probably ought to just
pull from my git trees, which are linked below.

This is an extraordinary way to destroy everything.  Enjoy!
Comments and questions are, as always, welcome.

--D

fstests git tree:
https://git.kernel.org/cgit/linux/kernel/git/djwong/xfstests-dev.git/log/?h=fix-alwayscow-tests
---
 common/xfs        |    9 +++++++++
 tests/generic/392 |   10 ++++++++++
 tests/xfs/080     |    1 +
 tests/xfs/182     |    1 +
 tests/xfs/192     |    1 +
 tests/xfs/198     |    1 +
 tests/xfs/204     |    1 +
 tests/xfs/211     |    1 +
 tests/xfs/326     |   12 ++++++++++++
 tests/xfs/329     |    1 +
 tests/xfs/434     |    1 +
 tests/xfs/436     |    1 +
 tests/xfs/558     |    6 ++++++
 13 files changed, 46 insertions(+)

[PATCH 1/3] xfs: skip fragmentation tests when alwayscow mode is enabled

[Darrick J. Wong]

From: Darrick J. Wong <djwong@kernel.org>

If the always_cow debugging flag is enabled, all file writes turn into
copy writes.  This dramatically ramps up fragmentation in the filesystem
(intentionally!) so there's no point in complaining about fragmentation.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 common/xfs    |    9 +++++++++
 tests/xfs/182 |    1 +
 tests/xfs/192 |    1 +
 tests/xfs/198 |    1 +
 tests/xfs/204 |    1 +
 tests/xfs/211 |    1 +
 6 files changed, 14 insertions(+)


diff --git a/common/xfs b/common/xfs
index 7eee76c0ee..a00d90a4b5 100644
--- a/common/xfs
+++ b/common/xfs
@@ -1108,6 +1108,15 @@ _require_no_xfs_bug_on_assert()
 	fi
 }
 
+# Require that XFS is not configured in always_cow mode.
+_require_no_xfs_always_cow()
+{
+	if [ -f /sys/fs/xfs/debug/always_cow ]; then
+		grep -q "1" /sys/fs/xfs/debug/always_cow && \
+		   _notrun "test requires XFS always_cow to be off, turn it off to run the test"
+	fi
+}
+
 # Get a metadata field
 # The first arg is the field name
 # The rest of the arguments are xfs_db commands to find the metadata.
diff --git a/tests/xfs/182 b/tests/xfs/182
index 696b933e60..511aca6f2d 100755
--- a/tests/xfs/182
+++ b/tests/xfs/182
@@ -24,6 +24,7 @@ _require_cp_reflink
 _require_xfs_io_command "fiemap"
 _require_xfs_io_command "cowextsize"
 _require_odirect
+_require_no_xfs_always_cow	# writes have to converge to overwrites
 
 echo "Format and mount"
 _scratch_mkfs > $seqres.full 2>&1
diff --git a/tests/xfs/192 b/tests/xfs/192
index ced18fa3c1..eb577f15fc 100755
--- a/tests/xfs/192
+++ b/tests/xfs/192
@@ -26,6 +26,7 @@ _require_xfs_io_command "fiemap"
 _require_xfs_io_command "cowextsize"
 _require_xfs_io_command "funshare"
 _require_odirect
+_require_no_xfs_always_cow	# writes have to converge to overwrites
 
 echo "Format and mount"
 _scratch_mkfs > $seqres.full 2>&1
diff --git a/tests/xfs/198 b/tests/xfs/198
index c61fbab70d..e5b98609de 100755
--- a/tests/xfs/198
+++ b/tests/xfs/198
@@ -23,6 +23,7 @@ _require_cp_reflink
 _require_xfs_io_command "fiemap"
 _require_xfs_io_command "cowextsize"
 _require_odirect
+_require_no_xfs_always_cow	# writes have to converge to overwrites
 
 echo "Format and mount"
 _scratch_mkfs > $seqres.full 2>&1
diff --git a/tests/xfs/204 b/tests/xfs/204
index ca21dfe722..7d6b79a86d 100755
--- a/tests/xfs/204
+++ b/tests/xfs/204
@@ -28,6 +28,7 @@ _require_xfs_io_command "fiemap"
 _require_xfs_io_command "cowextsize"
 _require_xfs_io_command "funshare"
 _require_odirect
+_require_no_xfs_always_cow	# writes have to converge to overwrites
 
 echo "Format and mount"
 _scratch_mkfs > $seqres.full 2>&1
diff --git a/tests/xfs/211 b/tests/xfs/211
index 96c0b85b14..3ce6496afc 100755
--- a/tests/xfs/211
+++ b/tests/xfs/211
@@ -24,6 +24,7 @@ _require_cp_reflink
 _require_xfs_io_command "fiemap"
 _require_xfs_io_command "cowextsize"
 _require_odirect
+_require_no_xfs_always_cow	# writes have to converge to overwrites
 
 echo "Format and mount"
 _scratch_mkfs > $seqres.full 2>&1

Re: [PATCH 1/3] xfs: skip fragmentation tests when alwayscow mode is enabled

[Christoph Hellwig]

On Tue, Jan 17, 2023 at 04:43:00PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
> 
> If the always_cow debugging flag is enabled, all file writes turn into
> copy writes.  This dramatically ramps up fragmentation in the filesystem
> (intentionally!) so there's no point in complaining about fragmentation.

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

[PATCH 2/3] xfs/{080,329,434,436}: add missing check for fallocate support

[Darrick J. Wong]

From: Darrick J. Wong <djwong@kernel.org>

Don't run this test if the filesystem doesn't support fallocate.  This
is only ever the case if always_cow is enabled.

The same logic applies to xfs/329, though it's more subtle because the
test itself does not explicitly invoke fallocate; rather, it is xfs_fsr
that requires fallocate.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 tests/xfs/080 |    1 +
 tests/xfs/329 |    1 +
 tests/xfs/434 |    1 +
 tests/xfs/436 |    1 +
 4 files changed, 4 insertions(+)


diff --git a/tests/xfs/080 b/tests/xfs/080
index 20b20a08eb..abcfa004b5 100755
--- a/tests/xfs/080
+++ b/tests/xfs/080
@@ -21,6 +21,7 @@ _cleanup()
 
 _supported_fs xfs
 _require_test
+_require_xfs_io_command falloc	# iogen requires falloc
 
 quiet=-q
 clean=-c
diff --git a/tests/xfs/329 b/tests/xfs/329
index 4cad686c17..15dc3c242f 100755
--- a/tests/xfs/329
+++ b/tests/xfs/329
@@ -22,6 +22,7 @@ _require_cp_reflink
 _require_command "$XFS_FSR_PROG" "xfs_fsr"
 _require_xfs_io_error_injection "bmap_finish_one"
 _require_xfs_scratch_rmapbt
+_require_xfs_io_command falloc	# fsr requires support for preallocation
 
 rm -f "$seqres.full"
 
diff --git a/tests/xfs/434 b/tests/xfs/434
index 576f1b0e1e..de52531053 100755
--- a/tests/xfs/434
+++ b/tests/xfs/434
@@ -35,6 +35,7 @@ _require_quota
 _require_scratch_reflink
 _require_cp_reflink
 _require_command "$XFS_FSR_PROG" "xfs_fsr"
+_require_xfs_io_command falloc # fsr requires support for preallocation
 _require_xfs_io_error_injection "bmap_finish_one"
 _require_xfs_scratch_rmapbt
 
diff --git a/tests/xfs/436 b/tests/xfs/436
index 9e6ec9372d..b95da8abf4 100755
--- a/tests/xfs/436
+++ b/tests/xfs/436
@@ -30,6 +30,7 @@ _supported_fs xfs
 _require_loadable_fs_module "xfs"
 _require_scratch_reflink
 _require_cp_reflink
+_require_xfs_io_command falloc # fsr requires support for preallocation
 _require_command "$XFS_FSR_PROG" "xfs_fsr"
 _require_xfs_io_error_injection "bmap_finish_one"
 _require_xfs_scratch_rmapbt

Re: [PATCH 2/3] xfs/{080,329,434,436}: add missing check for fallocate support

[Christoph Hellwig]

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

[PATCH 3/3] various: test is not appropriate for always_cow mode

[Darrick J. Wong]

From: Darrick J. Wong <djwong@kernel.org>

When always_cow mode is enabled, thes tests cannot set up the
preconditions for the functionality that they wants to test and should
be skipped.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 tests/generic/392 |   10 ++++++++++
 tests/xfs/326     |   12 ++++++++++++
 tests/xfs/558     |    6 ++++++
 3 files changed, 28 insertions(+)


diff --git a/tests/generic/392 b/tests/generic/392
index ac4014ab0c..c4bb3f4b92 100755
--- a/tests/generic/392
+++ b/tests/generic/392
@@ -28,6 +28,16 @@ _scratch_mkfs >/dev/null 2>&1
 _require_metadata_journaling $SCRATCH_DEV
 _scratch_mount
 
+# This test requires that i_blocks remains unchanged from the start of the
+# check_inode_metadata call until after recovery is complete.  fpunch calls
+# turn into pagecache writes if the arguments are not aligned to the fs
+# blocksize.  If the range being punched is already mapped to a written extent
+# and alwayscow is enabled, i_blocks will increase by the size of the COW
+# staging extent.  This causes stat to report different numbers for %b, which
+# results in a test failure.  Hence do not run this test if XFS is in alwayscow
+# mode.
+test "$FSTYP" = "xfs" && _require_no_xfs_always_cow
+
 testfile=$SCRATCH_MNT/testfile
 
 # check inode metadata after shutdown
diff --git a/tests/xfs/326 b/tests/xfs/326
index 8ab60684bf..ac620fc433 100755
--- a/tests/xfs/326
+++ b/tests/xfs/326
@@ -43,6 +43,18 @@ _scratch_mount >> $seqres.full
 _require_congruent_file_oplen $SCRATCH_MNT $blksz
 $XFS_IO_PROG -c "cowextsize $sz" $SCRATCH_MNT
 
+# This test uses a very large cowextszhint to manipulate the COW fork to
+# contain a large unwritten extent before injecting the error.  The goal is
+# that the write() will succeed, writeback will flush the dirty data to disk,
+# and writeback completion will shut down the filesystem when it tries to
+# remove the staging extent record from the refcount btree.  In other words,
+# this test ensures that XFS always finishes a COW completion it has started.
+#
+# This test isn't compatible with always_cow mode because the hole in the COW
+# fork left by the first write means that writeback tries to allocate a COW
+# staging extent for an unshared extent and trips over the injected error.
+_require_no_xfs_always_cow
+
 echo "Create files"
 _pwrite_byte 0x66 0 $sz $SCRATCH_MNT/file1 >> $seqres.full
 _cp_reflink $SCRATCH_MNT/file1 $SCRATCH_MNT/file2
diff --git a/tests/xfs/558 b/tests/xfs/558
index 819faf22bc..9e9b3be867 100755
--- a/tests/xfs/558
+++ b/tests/xfs/558
@@ -114,6 +114,12 @@ _require_xfs_io_error_injection "wb_delay_ms"
 _require_scratch_reflink
 _require_cp_reflink
 
+# This test races writeback of a pure overwrite of a data fork extent against
+# the creation of a speculative COW preallocation.  In alwayscow mode, there
+# are no pure overwrites, which means that a precondition of the test is not
+# satisfied, and this test should be skipped.
+_require_no_xfs_always_cow
+
 _scratch_mkfs >> $seqres.full
 _scratch_mount >> $seqres.full
 

Re: [PATCH 3/3] various: test is not appropriate for always_cow mode

[Christoph Hellwig]

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>