[PATCH v2] generic/622: increase sleep time for lazytime expiration

[PATCH v2] generic/622: increase sleep time for lazytime expiration

[Jan Prusakowski]

In generic/622, expire_timestamps() tests whether lazytime timestamp
updates are persisted after dirtytime expiration. It configures
dirtytime_expire_seconds to 1 second and enables continuous writeback
of dirty inodes, followed by sleeping for 2 seconds to allow the
asynchronous VFS flusher thread to expire the I_DIRTY_TIME inode,
invoke the filesystem's write_inode callback, and flush the dirty
metadata before the test executes _scratch_shutdown -f.

However, on filesystems or configurations with higher writeback
overhead -- such as F2FS with transparent compression enabled, where
compressed files cannot use inline data and writes use out-of-place
updates (OPU) with higher latency in the compression and writeback
pipeline -- the 2-second sleep window can occasionally be insufficient.
Because the inode is only eligible for expiration after 1 second, only
about 1 second remains in the 2-second sleep window for the flusher
thread to schedule, expire the inode, and mark the inode page dirty
before restore_expiration_settings resets dirtytime_expire_seconds to
24 hours and shutdown occurs. If the flusher thread is delayed, the
subsequent shutdown checkpoint ignores the unexpired I_DIRTY_TIME inode,
causing the test to intermittently fail with:

    FAIL: lazytime mtime wasn't persisted by expiration
    ondisk_time (...) != expected_time (...)

Increase the sleep duration in expire_timestamps() from 2 to 4 seconds
to give sufficient margin for the flusher thread to reliably expire the
lazytime inode and dirty the inode page before shutdown.

Signed-off-by: Jan Prusakowski <jprusakowski@google.com>
---
Changes in v2:
- Increase sleep time to 4 seconds unconditionally with an explanatory
  comment instead of using an F2FS-specific conditional.
- Remove the non-standard Change-Id trailer.

 tests/generic/622 | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/tests/generic/622 b/tests/generic/622
index cb0f5828..16088199 100755
--- a/tests/generic/622
+++ b/tests/generic/622
@@ -60,8 +60,12 @@ expire_timestamps()
 	__expire_inodes
 
 	# Userspace doesn't have direct visibility into when inodes are dirty,
-	# so the best we can do is sleep for a couple seconds.
-	sleep 2
+	# so the best we can do is sleep for a few seconds.  Because
+	# dirtytime_expire_seconds is 1 second, sleeping for 4 seconds leaves
+	# enough margin after expiration for background writeback to finish even
+	# on filesystems with higher writeback overhead (e.g. F2FS with file
+	# compression).
+	sleep 4
 	restore_expiration_settings
 }
 
-- 
2.56.0.360.g66cac248cb-goog

[f2fs-dev] [PATCH v2] generic/622: increase sleep time for lazytime expiration

[Jan Prusakowski via Linux-f2fs-devel]

In generic/622, expire_timestamps() tests whether lazytime timestamp
updates are persisted after dirtytime expiration. It configures
dirtytime_expire_seconds to 1 second and enables continuous writeback
of dirty inodes, followed by sleeping for 2 seconds to allow the
asynchronous VFS flusher thread to expire the I_DIRTY_TIME inode,
invoke the filesystem's write_inode callback, and flush the dirty
metadata before the test executes _scratch_shutdown -f.

However, on filesystems or configurations with higher writeback
overhead -- such as F2FS with transparent compression enabled, where
compressed files cannot use inline data and writes use out-of-place
updates (OPU) with higher latency in the compression and writeback
pipeline -- the 2-second sleep window can occasionally be insufficient.
Because the inode is only eligible for expiration after 1 second, only
about 1 second remains in the 2-second sleep window for the flusher
thread to schedule, expire the inode, and mark the inode page dirty
before restore_expiration_settings resets dirtytime_expire_seconds to
24 hours and shutdown occurs. If the flusher thread is delayed, the
subsequent shutdown checkpoint ignores the unexpired I_DIRTY_TIME inode,
causing the test to intermittently fail with:

    FAIL: lazytime mtime wasn't persisted by expiration
    ondisk_time (...) != expected_time (...)

Increase the sleep duration in expire_timestamps() from 2 to 4 seconds
to give sufficient margin for the flusher thread to reliably expire the
lazytime inode and dirty the inode page before shutdown.

Signed-off-by: Jan Prusakowski <jprusakowski@google.com>
---
Changes in v2:
- Increase sleep time to 4 seconds unconditionally with an explanatory
  comment instead of using an F2FS-specific conditional.
- Remove the non-standard Change-Id trailer.

 tests/generic/622 | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/tests/generic/622 b/tests/generic/622
index cb0f5828..16088199 100755
--- a/tests/generic/622
+++ b/tests/generic/622
@@ -60,8 +60,12 @@ expire_timestamps()
 	__expire_inodes
 
 	# Userspace doesn't have direct visibility into when inodes are dirty,
-	# so the best we can do is sleep for a couple seconds.
-	sleep 2
+	# so the best we can do is sleep for a few seconds.  Because
+	# dirtytime_expire_seconds is 1 second, sleeping for 4 seconds leaves
+	# enough margin after expiration for background writeback to finish even
+	# on filesystems with higher writeback overhead (e.g. F2FS with file
+	# compression).
+	sleep 4
 	restore_expiration_settings
 }
 
-- 
2.56.0.360.g66cac248cb-goog



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Re: [PATCH v2] generic/622: increase sleep time for lazytime expiration

[Christoph Hellwig]

Looks good:

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

Re: [f2fs-dev] [PATCH v2] generic/622: increase sleep time for lazytime expiration

[Christoph Hellwig]

Looks good:

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



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Re: [PATCH v2] generic/622: increase sleep time for lazytime expiration

[Chao Yu]

On 10/9/26 16:55, Jan Prusakowski wrote:
> In generic/622, expire_timestamps() tests whether lazytime timestamp
> updates are persisted after dirtytime expiration. It configures
> dirtytime_expire_seconds to 1 second and enables continuous writeback
> of dirty inodes, followed by sleeping for 2 seconds to allow the
> asynchronous VFS flusher thread to expire the I_DIRTY_TIME inode,
> invoke the filesystem's write_inode callback, and flush the dirty
> metadata before the test executes _scratch_shutdown -f.
> 
> However, on filesystems or configurations with higher writeback
> overhead -- such as F2FS with transparent compression enabled, where
> compressed files cannot use inline data and writes use out-of-place
> updates (OPU) with higher latency in the compression and writeback

FYI, I encounter similar issue on non-compressed inode, so v2 w/o checking
compression makes sense to me.

> pipeline -- the 2-second sleep window can occasionally be insufficient.
> Because the inode is only eligible for expiration after 1 second, only
> about 1 second remains in the 2-second sleep window for the flusher
> thread to schedule, expire the inode, and mark the inode page dirty
> before restore_expiration_settings resets dirtytime_expire_seconds to
> 24 hours and shutdown occurs. If the flusher thread is delayed, the
> subsequent shutdown checkpoint ignores the unexpired I_DIRTY_TIME inode,
> causing the test to intermittently fail with:
> 
>     FAIL: lazytime mtime wasn't persisted by expiration
>     ondisk_time (...) != expected_time (...)
> 
> Increase the sleep duration in expire_timestamps() from 2 to 4 seconds
> to give sufficient margin for the flusher thread to reliably expire the
> lazytime inode and dirty the inode page before shutdown.
> 
> Signed-off-by: Jan Prusakowski <jprusakowski@google.com>
Reviewed-by: Chao Yu <chao@kernel.org>

Thanks,

Re: [f2fs-dev] [PATCH v2] generic/622: increase sleep time for lazytime expiration

[Chao Yu via Linux-f2fs-devel]

On 10/9/26 16:55, Jan Prusakowski wrote:
> In generic/622, expire_timestamps() tests whether lazytime timestamp
> updates are persisted after dirtytime expiration. It configures
> dirtytime_expire_seconds to 1 second and enables continuous writeback
> of dirty inodes, followed by sleeping for 2 seconds to allow the
> asynchronous VFS flusher thread to expire the I_DIRTY_TIME inode,
> invoke the filesystem's write_inode callback, and flush the dirty
> metadata before the test executes _scratch_shutdown -f.
> 
> However, on filesystems or configurations with higher writeback
> overhead -- such as F2FS with transparent compression enabled, where
> compressed files cannot use inline data and writes use out-of-place
> updates (OPU) with higher latency in the compression and writeback

FYI, I encounter similar issue on non-compressed inode, so v2 w/o checking
compression makes sense to me.

> pipeline -- the 2-second sleep window can occasionally be insufficient.
> Because the inode is only eligible for expiration after 1 second, only
> about 1 second remains in the 2-second sleep window for the flusher
> thread to schedule, expire the inode, and mark the inode page dirty
> before restore_expiration_settings resets dirtytime_expire_seconds to
> 24 hours and shutdown occurs. If the flusher thread is delayed, the
> subsequent shutdown checkpoint ignores the unexpired I_DIRTY_TIME inode,
> causing the test to intermittently fail with:
> 
>     FAIL: lazytime mtime wasn't persisted by expiration
>     ondisk_time (...) != expected_time (...)
> 
> Increase the sleep duration in expire_timestamps() from 2 to 4 seconds
> to give sufficient margin for the flusher thread to reliably expire the
> lazytime inode and dirty the inode page before shutdown.
> 
> Signed-off-by: Jan Prusakowski <jprusakowski@google.com>
Reviewed-by: Chao Yu <chao@kernel.org>

Thanks,


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