[PATCH] generic/798: exclude nfs from cachestat dirty page reporting test

[PATCH] generic/798: exclude nfs from cachestat dirty page reporting test

[Avinesh Kumar]

From: Avinesh Kumar <avinesh.kumar@suse.com>

generic/798 checks cachestat() page cache dirty state between write and
fsync operations.

On NFS, the client flushes dirty pages to the server during close() to
enforce its close-to-open consistency model. Because the test uses separate
xfs_io invocations, the file is closed after writing, leaving pages already
clean by the time the subsequent cachestat command executes, causing the
test to fail.

- output mismatch (see /opt/xfstests/results//generic/798.out.bad)
    --- tests/generic/798.out	2026-08-20 05:25:39.000000000 -0400
    +++ /opt/xfstests/results//generic/798.out.bad	2026-08-21 12:30:39.831381108 -0400
    @@ -1,16 +1,16 @@
     QA output created by 798
     === Test with 1 pages ===
    -Cached: 1, Dirty: 1, Writeback: 0, Evicted: 0, Recently Evicted: 0
    +Cached: 1, Dirty: 0, Writeback: 0, Evicted: 0, Recently Evicted: 0
     Cached: 1, Dirty: 0, Writeback: 0, Evicted: 0, Recently Evicted: 0
     === Test with 2 pages ===
    -Cached: 2, Dirty: 2, Writeback: 0, Evicted: 0, Recently Evicted: 0
    ...

Exclude 'nfs' from running this test.

Signed-off-by: Avinesh Kumar <avinesh.kumar@suse.com>
---
 tests/generic/798 | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tests/generic/798 b/tests/generic/798
index 0fe37646..80b2acc9 100755
--- a/tests/generic/798
+++ b/tests/generic/798
@@ -16,6 +16,12 @@ _require_scratch
 _exclude_scratch_mount_option "dax"
 _exclude_scratch_mount_option "sync"
 
+# NFS flushes dirty data back to the server on close() as part of its
+# close-to-open cache consistency model, so a page written and closed in
+# one xfs_io invocation is no longer dirty by the time cachestat runs in
+# a later invocation.
+_exclude_fs nfs
+
 pagesize=$(_get_page_size)
 
 _scratch_mkfs > /dev/null
-- 
2.55.0

Re: [PATCH] generic/798: exclude nfs from cachestat dirty page reporting test

[Darrick J. Wong]

On Mon, Aug 24, 2026 at 05:11:06PM +0200, Avinesh Kumar wrote:
> From: Avinesh Kumar <avinesh.kumar@suse.com>
> 
> generic/798 checks cachestat() page cache dirty state between write and
> fsync operations.
> 
> On NFS, the client flushes dirty pages to the server during close() to
> enforce its close-to-open consistency model. Because the test uses separate
> xfs_io invocations, the file is closed after writing, leaving pages already
> clean by the time the subsequent cachestat command executes, causing the
> test to fail.
> 
> - output mismatch (see /opt/xfstests/results//generic/798.out.bad)
>     --- tests/generic/798.out	2026-08-20 05:25:39.000000000 -0400
>     +++ /opt/xfstests/results//generic/798.out.bad	2026-08-21 12:30:39.831381108 -0400
>     @@ -1,16 +1,16 @@
>      QA output created by 798
>      === Test with 1 pages ===
>     -Cached: 1, Dirty: 1, Writeback: 0, Evicted: 0, Recently Evicted: 0
>     +Cached: 1, Dirty: 0, Writeback: 0, Evicted: 0, Recently Evicted: 0
>      Cached: 1, Dirty: 0, Writeback: 0, Evicted: 0, Recently Evicted: 0
>      === Test with 2 pages ===
>     -Cached: 2, Dirty: 2, Writeback: 0, Evicted: 0, Recently Evicted: 0
>     ...
> 
> Exclude 'nfs' from running this test.
> 
> Signed-off-by: Avinesh Kumar <avinesh.kumar@suse.com>
> ---
>  tests/generic/798 | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/tests/generic/798 b/tests/generic/798
> index 0fe37646..80b2acc9 100755
> --- a/tests/generic/798
> +++ b/tests/generic/798
> @@ -16,6 +16,12 @@ _require_scratch
>  _exclude_scratch_mount_option "dax"
>  _exclude_scratch_mount_option "sync"
>  
> +# NFS flushes dirty data back to the server on close() as part of its
> +# close-to-open cache consistency model, so a page written and closed in
> +# one xfs_io invocation is no longer dirty by the time cachestat runs in
> +# a later invocation.
> +_exclude_fs nfs

Could you just chain all the xfs_io commands together into a single
invocation?

$XFS_IO_PROG -f \
	-c "pwrite -b $pagesize 0 $size" \
	-c "cachestat 0 $size" \
	-c "fsync" \
	-c "cachestat 0 $size" \
	$SCRATCH_MNT/foobar

to solve this problem?

--D

> +
>  pagesize=$(_get_page_size)
>  
>  _scratch_mkfs > /dev/null
> -- 
> 2.55.0
> 
> 

Re: [PATCH] generic/798: exclude nfs from cachestat dirty page reporting test

[Avinesh Kumar]

Hello Darrick,


>> diff --git a/tests/generic/798 b/tests/generic/798
>> index 0fe37646..80b2acc9 100755
>> --- a/tests/generic/798
>> +++ b/tests/generic/798
>> @@ -16,6 +16,12 @@ _require_scratch
>>   _exclude_scratch_mount_option "dax"
>>   _exclude_scratch_mount_option "sync"
>>   
>> +# NFS flushes dirty data back to the server on close() as part of its
>> +# close-to-open cache consistency model, so a page written and closed in
>> +# one xfs_io invocation is no longer dirty by the time cachestat runs in
>> +# a later invocation.
>> +_exclude_fs nfs
> 
> Could you just chain all the xfs_io commands together into a single
> invocation?
> 
> $XFS_IO_PROG -f \
> 	-c "pwrite -b $pagesize 0 $size" \
> 	-c "cachestat 0 $size" \
> 	-c "fsync" \
> 	-c "cachestat 0 $size" \
> 	$SCRATCH_MNT/foobar
> 
> to solve this problem?
> 

Thanks for the review and this suggestion. Chaining all xfs_io commands
together seems to work, with also passing '-q' to pwrite to suppress
these lines -
     +wrote 4096/4096 bytes at offset 0
     +4 KiB, 1 ops; 0.0000 sec (355.114 MiB/sec and 90909.0909 ops/sec)

I am sending revised patch.

Regards,
Avinesh

[PATCH v2] generic/798: chain xfs_io commands into a single invocation

[Avinesh Kumar]

From: Avinesh Kumar <avinesh.kumar@suse.com>

The write, cachestat, fsync, and cachestat calls were each run as
separate xfs_io invocations, closing and reopening the file in
between. Some filesystems flush dirty data back on close(), clearing
the dirty bit before the first cachestat ever ran, causing test failure

- output mismatch (see /opt/xfstests/results//generic/798.out.bad)
    --- tests/generic/798.out	2026-08-20 05:25:39.000000000 -0400
    +++ /opt/xfstests/results//generic/798.out.bad	2026-08-21 12:30:39.831381108 -0400
    @@ -1,16 +1,16 @@
     QA output created by 798
     === Test with 1 pages ===
    -Cached: 1, Dirty: 1, Writeback: 0, Evicted: 0, Recently Evicted: 0
    +Cached: 1, Dirty: 0, Writeback: 0, Evicted: 0, Recently Evicted: 0
     Cached: 1, Dirty: 0, Writeback: 0, Evicted: 0, Recently Evicted: 0
     === Test with 2 pages ===
    -Cached: 2, Dirty: 2, Writeback: 0, Evicted: 0, Recently Evicted: 0
    ...

Run the whole sequence on one open file descriptor instead by chaining
all xfs_io commands in single invocation.

Suggested-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Avinesh Kumar <avinesh.kumar@suse.com>
---
 tests/generic/798 | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/tests/generic/798 b/tests/generic/798
index 0fe37646..171878ee 100755
--- a/tests/generic/798
+++ b/tests/generic/798
@@ -27,12 +27,22 @@ for num_page in 1 2 4 8 16; do
 	echo "=== Test with $num_page pages ==="
 
 	rm -f $SCRATCH_MNT/foobar
-	$XFS_IO_PROG -f -c "pwrite -b $pagesize 0 $size" $SCRATCH_MNT/foobar > /dev/null
-	# Basic cached number reporting
-	$XFS_IO_PROG -c "cachestat 0 $size" $SCRATCH_MNT/foobar
 
-	# Test dirty page number reporting after a fsync.
+	# Basic cached number reporting and test dirty page number
+	# reporting after a fsync.
+	#
+	# Do the whole write+cachestat+fsync+cachestat sequence in a
+	# single xfs_io invocation. Some filesystems (e.g. NFS) flush
+	# dirty data back to the server as part of their own close()-time
+	# cache consistency, which would clear the dirty bits before the
+	# second xfs_io process ever got to run cachestat.
 	$XFS_IO_PROG -c "fsync" -c "cachestat 0 $size" $SCRATCH_MNT/foobar
+		$XFS_IO_PROG -f \
+		-c "pwrite -q -b $pagesize 0 $size" \
+		-c "cachestat 0 $size" \
+		-c "fsync" \
+		-c "cachestat 0 $size" \
+		$SCRATCH_MNT/foobar
 done
 
 _scratch_unmount
-- 
2.55.0

Re: [PATCH v2] generic/798: chain xfs_io commands into a single invocation

[Darrick J. Wong]

On Wed, Aug 26, 2026 at 05:01:14PM +0200, Avinesh Kumar wrote:
> From: Avinesh Kumar <avinesh.kumar@suse.com>
> 
> The write, cachestat, fsync, and cachestat calls were each run as
> separate xfs_io invocations, closing and reopening the file in
> between. Some filesystems flush dirty data back on close(), clearing
> the dirty bit before the first cachestat ever ran, causing test failure
> 
> - output mismatch (see /opt/xfstests/results//generic/798.out.bad)
>     --- tests/generic/798.out	2026-08-20 05:25:39.000000000 -0400
>     +++ /opt/xfstests/results//generic/798.out.bad	2026-08-21 12:30:39.831381108 -0400
>     @@ -1,16 +1,16 @@
>      QA output created by 798
>      === Test with 1 pages ===
>     -Cached: 1, Dirty: 1, Writeback: 0, Evicted: 0, Recently Evicted: 0
>     +Cached: 1, Dirty: 0, Writeback: 0, Evicted: 0, Recently Evicted: 0
>      Cached: 1, Dirty: 0, Writeback: 0, Evicted: 0, Recently Evicted: 0
>      === Test with 2 pages ===
>     -Cached: 2, Dirty: 2, Writeback: 0, Evicted: 0, Recently Evicted: 0
>     ...
> 
> Run the whole sequence on one open file descriptor instead by chaining
> all xfs_io commands in single invocation.
> 
> Suggested-by: "Darrick J. Wong" <djwong@kernel.org>
> Signed-off-by: Avinesh Kumar <avinesh.kumar@suse.com>
> ---
>  tests/generic/798 | 18 ++++++++++++++----
>  1 file changed, 14 insertions(+), 4 deletions(-)
> 
> diff --git a/tests/generic/798 b/tests/generic/798
> index 0fe37646..171878ee 100755
> --- a/tests/generic/798
> +++ b/tests/generic/798
> @@ -27,12 +27,22 @@ for num_page in 1 2 4 8 16; do
>  	echo "=== Test with $num_page pages ==="
>  
>  	rm -f $SCRATCH_MNT/foobar
> -	$XFS_IO_PROG -f -c "pwrite -b $pagesize 0 $size" $SCRATCH_MNT/foobar > /dev/null
> -	# Basic cached number reporting
> -	$XFS_IO_PROG -c "cachestat 0 $size" $SCRATCH_MNT/foobar
>  
> -	# Test dirty page number reporting after a fsync.
> +	# Basic cached number reporting and test dirty page number
> +	# reporting after a fsync.
> +	#
> +	# Do the whole write+cachestat+fsync+cachestat sequence in a
> +	# single xfs_io invocation. Some filesystems (e.g. NFS) flush
> +	# dirty data back to the server as part of their own close()-time
> +	# cache consistency, which would clear the dirty bits before the
> +	# second xfs_io process ever got to run cachestat.
>  	$XFS_IO_PROG -c "fsync" -c "cachestat 0 $size" $SCRATCH_MNT/foobar
> +		$XFS_IO_PROG -f \

Not sure why there are two $XFS_IO_PROG invocations here??

Also the first line of the second invocation should only be indented one
tab, not two.

--D

> +		-c "pwrite -q -b $pagesize 0 $size" \
> +		-c "cachestat 0 $size" \
> +		-c "fsync" \
> +		-c "cachestat 0 $size" \
> +		$SCRATCH_MNT/foobar
>  done
>  
>  _scratch_unmount
> -- 
> 2.55.0
> 
> 

[PATCH v3] generic/798: chain xfs_io commands into a single invocation

[Avinesh Kumar]

From: Avinesh Kumar <avinesh.kumar@suse.com>

The write, cachestat, fsync, and cachestat calls were each run as
separate xfs_io invocations, closing and reopening the file in
between. Some filesystems flush dirty data back on close(), clearing
the dirty bit before the first cachestat ever ran, causing test failure

- output mismatch (see /opt/xfstests/results//generic/798.out.bad)
    --- tests/generic/798.out	2026-08-20 05:25:39.000000000 -0400
    +++ /opt/xfstests/results//generic/798.out.bad	2026-08-21 12:30:39.831381108 -0400
    @@ -1,16 +1,16 @@
     QA output created by 798
     === Test with 1 pages ===
    -Cached: 1, Dirty: 1, Writeback: 0, Evicted: 0, Recently Evicted: 0
    +Cached: 1, Dirty: 0, Writeback: 0, Evicted: 0, Recently Evicted: 0
     Cached: 1, Dirty: 0, Writeback: 0, Evicted: 0, Recently Evicted: 0
     === Test with 2 pages ===
    -Cached: 2, Dirty: 2, Writeback: 0, Evicted: 0, Recently Evicted: 0
    ...

Run the whole sequence on one open file descriptor instead by chaining
all xfs_io commands in single invocation.

Suggested-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Avinesh Kumar <avinesh.kumar@suse.com>
---
 tests/generic/798 | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/tests/generic/798 b/tests/generic/798
index 0fe37646..5c81b429 100755
--- a/tests/generic/798
+++ b/tests/generic/798
@@ -27,12 +27,21 @@ for num_page in 1 2 4 8 16; do
 	echo "=== Test with $num_page pages ==="
 
 	rm -f $SCRATCH_MNT/foobar
-	$XFS_IO_PROG -f -c "pwrite -b $pagesize 0 $size" $SCRATCH_MNT/foobar > /dev/null
-	# Basic cached number reporting
-	$XFS_IO_PROG -c "cachestat 0 $size" $SCRATCH_MNT/foobar
 
-	# Test dirty page number reporting after a fsync.
-	$XFS_IO_PROG -c "fsync" -c "cachestat 0 $size" $SCRATCH_MNT/foobar
+	# Basic cached number reporting and test dirty page number
+	# reporting after a fsync.
+	#
+	# Do the whole write+cachestat+fsync+cachestat sequence in a
+	# single xfs_io invocation. Some filesystems (e.g. NFS) flush
+	# dirty data back to the server as part of their own close()-time
+	# cache consistency, which would clear the dirty bits before the
+	# second xfs_io process ever got to run cachestat.
+	$XFS_IO_PROG -f \
+		-c "pwrite -q -b $pagesize 0 $size" \
+		-c "cachestat 0 $size" \
+		-c "fsync" \
+		-c "cachestat 0 $size" \
+		$SCRATCH_MNT/foobar
 done
 
 _scratch_unmount
-- 
2.55.0

Re: [PATCH v3] generic/798: chain xfs_io commands into a single invocation

[Darrick J. Wong]

On Wed, Aug 26, 2026 at 05:54:23PM +0200, Avinesh Kumar wrote:
> From: Avinesh Kumar <avinesh.kumar@suse.com>
> 
> The write, cachestat, fsync, and cachestat calls were each run as
> separate xfs_io invocations, closing and reopening the file in
> between. Some filesystems flush dirty data back on close(), clearing
> the dirty bit before the first cachestat ever ran, causing test failure
> 
> - output mismatch (see /opt/xfstests/results//generic/798.out.bad)
>     --- tests/generic/798.out	2026-08-20 05:25:39.000000000 -0400
>     +++ /opt/xfstests/results//generic/798.out.bad	2026-08-21 12:30:39.831381108 -0400
>     @@ -1,16 +1,16 @@
>      QA output created by 798
>      === Test with 1 pages ===
>     -Cached: 1, Dirty: 1, Writeback: 0, Evicted: 0, Recently Evicted: 0
>     +Cached: 1, Dirty: 0, Writeback: 0, Evicted: 0, Recently Evicted: 0
>      Cached: 1, Dirty: 0, Writeback: 0, Evicted: 0, Recently Evicted: 0
>      === Test with 2 pages ===
>     -Cached: 2, Dirty: 2, Writeback: 0, Evicted: 0, Recently Evicted: 0
>     ...
> 
> Run the whole sequence on one open file descriptor instead by chaining
> all xfs_io commands in single invocation.
> 
> Suggested-by: "Darrick J. Wong" <djwong@kernel.org>
> Signed-off-by: Avinesh Kumar <avinesh.kumar@suse.com>

Looks good now!
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
>  tests/generic/798 | 19 ++++++++++++++-----
>  1 file changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/tests/generic/798 b/tests/generic/798
> index 0fe37646..5c81b429 100755
> --- a/tests/generic/798
> +++ b/tests/generic/798
> @@ -27,12 +27,21 @@ for num_page in 1 2 4 8 16; do
>  	echo "=== Test with $num_page pages ==="
>  
>  	rm -f $SCRATCH_MNT/foobar
> -	$XFS_IO_PROG -f -c "pwrite -b $pagesize 0 $size" $SCRATCH_MNT/foobar > /dev/null
> -	# Basic cached number reporting
> -	$XFS_IO_PROG -c "cachestat 0 $size" $SCRATCH_MNT/foobar
>  
> -	# Test dirty page number reporting after a fsync.
> -	$XFS_IO_PROG -c "fsync" -c "cachestat 0 $size" $SCRATCH_MNT/foobar
> +	# Basic cached number reporting and test dirty page number
> +	# reporting after a fsync.
> +	#
> +	# Do the whole write+cachestat+fsync+cachestat sequence in a
> +	# single xfs_io invocation. Some filesystems (e.g. NFS) flush
> +	# dirty data back to the server as part of their own close()-time
> +	# cache consistency, which would clear the dirty bits before the
> +	# second xfs_io process ever got to run cachestat.
> +	$XFS_IO_PROG -f \
> +		-c "pwrite -q -b $pagesize 0 $size" \
> +		-c "cachestat 0 $size" \
> +		-c "fsync" \
> +		-c "cachestat 0 $size" \
> +		$SCRATCH_MNT/foobar
>  done
>  
>  _scratch_unmount
> -- 
> 2.55.0
> 
> 

Re: [PATCH v3] generic/798: chain xfs_io commands into a single invocation

[Zorro Lang]

On Wed, Aug 26, 2026 at 05:54:23PM +0200, Avinesh Kumar wrote:
> From: Avinesh Kumar <avinesh.kumar@suse.com>
> 
> The write, cachestat, fsync, and cachestat calls were each run as
> separate xfs_io invocations, closing and reopening the file in
> between. Some filesystems flush dirty data back on close(), clearing
> the dirty bit before the first cachestat ever ran, causing test failure
> 
> - output mismatch (see /opt/xfstests/results//generic/798.out.bad)
>     --- tests/generic/798.out	2026-08-20 05:25:39.000000000 -0400
>     +++ /opt/xfstests/results//generic/798.out.bad	2026-08-21 12:30:39.831381108 -0400
>     @@ -1,16 +1,16 @@
>      QA output created by 798
>      === Test with 1 pages ===
>     -Cached: 1, Dirty: 1, Writeback: 0, Evicted: 0, Recently Evicted: 0
>     +Cached: 1, Dirty: 0, Writeback: 0, Evicted: 0, Recently Evicted: 0
>      Cached: 1, Dirty: 0, Writeback: 0, Evicted: 0, Recently Evicted: 0
>      === Test with 2 pages ===
>     -Cached: 2, Dirty: 2, Writeback: 0, Evicted: 0, Recently Evicted: 0
>     ...
> 
> Run the whole sequence on one open file descriptor instead by chaining
> all xfs_io commands in single invocation.
> 
> Suggested-by: "Darrick J. Wong" <djwong@kernel.org>
> Signed-off-by: Avinesh Kumar <avinesh.kumar@suse.com>
> ---

This change is good to me,

Reviewed-by: Zorro Lang <zlang@kernel.org>

>  tests/generic/798 | 19 ++++++++++++++-----
>  1 file changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/tests/generic/798 b/tests/generic/798
> index 0fe37646..5c81b429 100755
> --- a/tests/generic/798
> +++ b/tests/generic/798
> @@ -27,12 +27,21 @@ for num_page in 1 2 4 8 16; do
>  	echo "=== Test with $num_page pages ==="
>  
>  	rm -f $SCRATCH_MNT/foobar
> -	$XFS_IO_PROG -f -c "pwrite -b $pagesize 0 $size" $SCRATCH_MNT/foobar > /dev/null
> -	# Basic cached number reporting
> -	$XFS_IO_PROG -c "cachestat 0 $size" $SCRATCH_MNT/foobar
>  
> -	# Test dirty page number reporting after a fsync.
> -	$XFS_IO_PROG -c "fsync" -c "cachestat 0 $size" $SCRATCH_MNT/foobar
> +	# Basic cached number reporting and test dirty page number
> +	# reporting after a fsync.
> +	#
> +	# Do the whole write+cachestat+fsync+cachestat sequence in a
> +	# single xfs_io invocation. Some filesystems (e.g. NFS) flush
> +	# dirty data back to the server as part of their own close()-time
> +	# cache consistency, which would clear the dirty bits before the
> +	# second xfs_io process ever got to run cachestat.
> +	$XFS_IO_PROG -f \
> +		-c "pwrite -q -b $pagesize 0 $size" \
> +		-c "cachestat 0 $size" \
> +		-c "fsync" \
> +		-c "cachestat 0 $size" \
> +		$SCRATCH_MNT/foobar
>  done
>  
>  _scratch_unmount
> -- 
> 2.55.0
> 
> 

Re: [PATCH v3] generic/798: chain xfs_io commands into a single invocation

[Qu Wenruo]

在 2026/8/27 01:24, Avinesh Kumar 写道:
> From: Avinesh Kumar <avinesh.kumar@suse.com>
> 
> The write, cachestat, fsync, and cachestat calls were each run as
> separate xfs_io invocations, closing and reopening the file in
> between. Some filesystems flush dirty data back on close(), clearing
> the dirty bit before the first cachestat ever ran, causing test failure
> 
> - output mismatch (see /opt/xfstests/results//generic/798.out.bad)
>      --- tests/generic/798.out	2026-08-20 05:25:39.000000000 -0400
>      +++ /opt/xfstests/results//generic/798.out.bad	2026-08-21 12:30:39.831381108 -0400
>      @@ -1,16 +1,16 @@
>       QA output created by 798
>       === Test with 1 pages ===
>      -Cached: 1, Dirty: 1, Writeback: 0, Evicted: 0, Recently Evicted: 0
>      +Cached: 1, Dirty: 0, Writeback: 0, Evicted: 0, Recently Evicted: 0
>       Cached: 1, Dirty: 0, Writeback: 0, Evicted: 0, Recently Evicted: 0
>       === Test with 2 pages ===
>      -Cached: 2, Dirty: 2, Writeback: 0, Evicted: 0, Recently Evicted: 0
>      ...
> 
> Run the whole sequence on one open file descriptor instead by chaining
> all xfs_io commands in single invocation.
> 
> Suggested-by: "Darrick J. Wong" <djwong@kernel.org>
> Signed-off-by: Avinesh Kumar <avinesh.kumar@suse.com>

Reviewed-by: Qu Wenruo <wqu@suse.com>

Thanks,
Qu

> ---
>   tests/generic/798 | 19 ++++++++++++++-----
>   1 file changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/tests/generic/798 b/tests/generic/798
> index 0fe37646..5c81b429 100755
> --- a/tests/generic/798
> +++ b/tests/generic/798
> @@ -27,12 +27,21 @@ for num_page in 1 2 4 8 16; do
>   	echo "=== Test with $num_page pages ==="
>   
>   	rm -f $SCRATCH_MNT/foobar
> -	$XFS_IO_PROG -f -c "pwrite -b $pagesize 0 $size" $SCRATCH_MNT/foobar > /dev/null
> -	# Basic cached number reporting
> -	$XFS_IO_PROG -c "cachestat 0 $size" $SCRATCH_MNT/foobar
>   
> -	# Test dirty page number reporting after a fsync.
> -	$XFS_IO_PROG -c "fsync" -c "cachestat 0 $size" $SCRATCH_MNT/foobar
> +	# Basic cached number reporting and test dirty page number
> +	# reporting after a fsync.
> +	#
> +	# Do the whole write+cachestat+fsync+cachestat sequence in a
> +	# single xfs_io invocation. Some filesystems (e.g. NFS) flush
> +	# dirty data back to the server as part of their own close()-time
> +	# cache consistency, which would clear the dirty bits before the
> +	# second xfs_io process ever got to run cachestat.
> +	$XFS_IO_PROG -f \
> +		-c "pwrite -q -b $pagesize 0 $size" \
> +		-c "cachestat 0 $size" \
> +		-c "fsync" \
> +		-c "cachestat 0 $size" \
> +		$SCRATCH_MNT/foobar
>   done
>   
>   _scratch_unmount