* [PATCH] design: fix computation of buffer log item bitmap size
@ 2021-11-10 1:58 Darrick J. Wong
2021-12-22 22:08 ` Darrick J. Wong
2021-12-23 6:06 ` Chandan Babu R
0 siblings, 2 replies; 4+ messages in thread
From: Darrick J. Wong @ 2021-11-10 1:58 UTC (permalink / raw)
To: xfs; +Cc: Wengang Wang
From: Darrick J. Wong <djwong@kernel.org>
Wengang Wang was trying to work through a buffer log item by consulting
the ondisk format documentation, and was confused by the formula given
in section 14.3.14 regarding the size of blf_data_map, aka the dirty
bitmap for buffer log items. We noticed that the documentation doesn't
match what the kernel actually does, so let's fix this.
Reported-by: Wengang Wang <wen.gang.wang@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
.../journaling_log.asciidoc | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/design/XFS_Filesystem_Structure/journaling_log.asciidoc b/design/XFS_Filesystem_Structure/journaling_log.asciidoc
index 1dba56e..894d3e5 100644
--- a/design/XFS_Filesystem_Structure/journaling_log.asciidoc
+++ b/design/XFS_Filesystem_Structure/journaling_log.asciidoc
@@ -992,7 +992,7 @@ The size of +blf_data_map+, in 32-bit words.
This variable-sized array acts as a dirty bitmap for the logged buffer. Each
1 bit represents a dirty region in the buffer, and each run of 1 bits
corresponds to a subsequent log item containing the new contents of the buffer
-area. Each bit represents +(blf_len * 512) / (blf_map_size * NBBY)+ bytes.
+area. Each bit represents +(blf_len * 512) / (blf_map_size * sizeof(unsigned int) * NBBY)+ bytes.
[[Buffer_Data_Log_Item]]
=== Buffer Data Log Item
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] design: fix computation of buffer log item bitmap size
2021-11-10 1:58 [PATCH] design: fix computation of buffer log item bitmap size Darrick J. Wong
@ 2021-12-22 22:08 ` Darrick J. Wong
2021-12-23 6:06 ` Chandan Babu R
1 sibling, 0 replies; 4+ messages in thread
From: Darrick J. Wong @ 2021-12-22 22:08 UTC (permalink / raw)
To: xfs; +Cc: Wengang Wang
On Tue, Nov 09, 2021 at 05:58:20PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
>
> Wengang Wang was trying to work through a buffer log item by consulting
> the ondisk format documentation, and was confused by the formula given
> in section 14.3.14 regarding the size of blf_data_map, aka the dirty
> bitmap for buffer log items. We noticed that the documentation doesn't
> match what the kernel actually does, so let's fix this.
>
> Reported-by: Wengang Wang <wen.gang.wang@oracle.com>
> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
This is probably a bad time for this, but... ping?
--D
> ---
> .../journaling_log.asciidoc | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/design/XFS_Filesystem_Structure/journaling_log.asciidoc b/design/XFS_Filesystem_Structure/journaling_log.asciidoc
> index 1dba56e..894d3e5 100644
> --- a/design/XFS_Filesystem_Structure/journaling_log.asciidoc
> +++ b/design/XFS_Filesystem_Structure/journaling_log.asciidoc
> @@ -992,7 +992,7 @@ The size of +blf_data_map+, in 32-bit words.
> This variable-sized array acts as a dirty bitmap for the logged buffer. Each
> 1 bit represents a dirty region in the buffer, and each run of 1 bits
> corresponds to a subsequent log item containing the new contents of the buffer
> -area. Each bit represents +(blf_len * 512) / (blf_map_size * NBBY)+ bytes.
> +area. Each bit represents +(blf_len * 512) / (blf_map_size * sizeof(unsigned int) * NBBY)+ bytes.
>
> [[Buffer_Data_Log_Item]]
> === Buffer Data Log Item
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] design: fix computation of buffer log item bitmap size
2021-11-10 1:58 [PATCH] design: fix computation of buffer log item bitmap size Darrick J. Wong
2021-12-22 22:08 ` Darrick J. Wong
@ 2021-12-23 6:06 ` Chandan Babu R
2022-01-04 1:44 ` Darrick J. Wong
1 sibling, 1 reply; 4+ messages in thread
From: Chandan Babu R @ 2021-12-23 6:06 UTC (permalink / raw)
To: Darrick J. Wong; +Cc: xfs, Wengang Wang
On 10 Nov 2021 at 07:28, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
>
> Wengang Wang was trying to work through a buffer log item by consulting
> the ondisk format documentation, and was confused by the formula given
> in section 14.3.14 regarding the size of blf_data_map, aka the dirty
> bitmap for buffer log items. We noticed that the documentation doesn't
> match what the kernel actually does, so let's fix this.
>
> Reported-by: Wengang Wang <wen.gang.wang@oracle.com>
> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> ---
> .../journaling_log.asciidoc | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/design/XFS_Filesystem_Structure/journaling_log.asciidoc b/design/XFS_Filesystem_Structure/journaling_log.asciidoc
> index 1dba56e..894d3e5 100644
> --- a/design/XFS_Filesystem_Structure/journaling_log.asciidoc
> +++ b/design/XFS_Filesystem_Structure/journaling_log.asciidoc
> @@ -992,7 +992,7 @@ The size of +blf_data_map+, in 32-bit words.
> This variable-sized array acts as a dirty bitmap for the logged buffer. Each
> 1 bit represents a dirty region in the buffer, and each run of 1 bits
> corresponds to a subsequent log item containing the new contents of the buffer
> -area. Each bit represents +(blf_len * 512) / (blf_map_size * NBBY)+ bytes.
> +area. Each bit represents +(blf_len * 512) / (blf_map_size * sizeof(unsigned int) * NBBY)+ bytes.
>
> [[Buffer_Data_Log_Item]]
> === Buffer Data Log Item
The calculation looks correct. However, wouldn't it be better to mention,
"Each bit represents XFS_BLF_CHUNK (i.e. 128) bytes"
... or some such variant involving XFS_BLF_CHUNK.
--
chandan
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] design: fix computation of buffer log item bitmap size
2021-12-23 6:06 ` Chandan Babu R
@ 2022-01-04 1:44 ` Darrick J. Wong
0 siblings, 0 replies; 4+ messages in thread
From: Darrick J. Wong @ 2022-01-04 1:44 UTC (permalink / raw)
To: Chandan Babu R; +Cc: xfs, Wengang Wang
On Thu, Dec 23, 2021 at 11:36:15AM +0530, Chandan Babu R wrote:
> On 10 Nov 2021 at 07:28, Darrick J. Wong wrote:
> > From: Darrick J. Wong <djwong@kernel.org>
> >
> > Wengang Wang was trying to work through a buffer log item by consulting
> > the ondisk format documentation, and was confused by the formula given
> > in section 14.3.14 regarding the size of blf_data_map, aka the dirty
> > bitmap for buffer log items. We noticed that the documentation doesn't
> > match what the kernel actually does, so let's fix this.
> >
> > Reported-by: Wengang Wang <wen.gang.wang@oracle.com>
> > Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> > ---
> > .../journaling_log.asciidoc | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/design/XFS_Filesystem_Structure/journaling_log.asciidoc b/design/XFS_Filesystem_Structure/journaling_log.asciidoc
> > index 1dba56e..894d3e5 100644
> > --- a/design/XFS_Filesystem_Structure/journaling_log.asciidoc
> > +++ b/design/XFS_Filesystem_Structure/journaling_log.asciidoc
> > @@ -992,7 +992,7 @@ The size of +blf_data_map+, in 32-bit words.
> > This variable-sized array acts as a dirty bitmap for the logged buffer. Each
> > 1 bit represents a dirty region in the buffer, and each run of 1 bits
> > corresponds to a subsequent log item containing the new contents of the buffer
> > -area. Each bit represents +(blf_len * 512) / (blf_map_size * NBBY)+ bytes.
> > +area. Each bit represents +(blf_len * 512) / (blf_map_size * sizeof(unsigned int) * NBBY)+ bytes.
> >
> > [[Buffer_Data_Log_Item]]
> > === Buffer Data Log Item
>
> The calculation looks correct. However, wouldn't it be better to mention,
>
> "Each bit represents XFS_BLF_CHUNK (i.e. 128) bytes"
>
> ... or some such variant involving XFS_BLF_CHUNK.
Ok.
--D
>
> --
> chandan
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2022-01-04 1:44 UTC | newest]
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2021-11-10 1:58 [PATCH] design: fix computation of buffer log item bitmap size Darrick J. Wong
2021-12-22 22:08 ` Darrick J. Wong
2021-12-23 6:06 ` Chandan Babu R
2022-01-04 1:44 ` Darrick J. Wong
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