[PATCH] fstrim: document kernel return minlen explictly

[PATCH] fstrim: document kernel return minlen explictly

[Wang Shilong]

From: Wang Shilong <wshilong@ddn.com>

Filesystem will modify @minlen according to its
block size etc, and will return actual unit
to userspace, document it into manpage.

Cc: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Wang Shilong <wshilong@ddn.com>
---
 sys-utils/fstrim.8 | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/sys-utils/fstrim.8 b/sys-utils/fstrim.8
index f7e7aa9ef..10ef8bc23 100644
--- a/sys-utils/fstrim.8
+++ b/sys-utils/fstrim.8
@@ -76,10 +76,10 @@ the end of the filesystem.
 .IP "\fB\-m, \-\-minimum\fP \fIminimum-size\fP"
 Minimum contiguous free range to discard, in bytes. (This value is internally
 rounded up to a multiple of the filesystem block size.)  Free ranges smaller
-than this will be ignored.  By increasing this value, the fstrim operation
-will complete more quickly for filesystems with badly fragmented freespace,
-although not all blocks will be discarded.  The default value is zero,
-discarding every free block.
+than this will be ignored and kernel shall return modified value(fstrim_range.minlen)
+to userspace. By increasing this value, the fstrim operation will complete
+more quickly for filesystems with badly fragmented freespace, although not
+all blocks will be discarded.  The default value is zero, discarding every free block.
 .IP "\fB\-v, \-\-verbose\fP"
 Verbose execution.  With this option
 .B fstrim
-- 
2.21.0

Re: [PATCH] fstrim: document kernel return minlen explictly

[Darrick J. Wong]

On Fri, Apr 19, 2019 at 11:37:20PM +0900, Wang Shilong wrote:
> From: Wang Shilong <wshilong@ddn.com>
> 
> Filesystem will modify @minlen according to its
> block size etc, and will return actual unit
> to userspace, document it into manpage.
> 
> Cc: Darrick J. Wong <darrick.wong@oracle.com>
> Signed-off-by: Wang Shilong <wshilong@ddn.com>
> ---
>  sys-utils/fstrim.8 | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/sys-utils/fstrim.8 b/sys-utils/fstrim.8
> index f7e7aa9ef..10ef8bc23 100644
> --- a/sys-utils/fstrim.8
> +++ b/sys-utils/fstrim.8
> @@ -76,10 +76,10 @@ the end of the filesystem.
>  .IP "\fB\-m, \-\-minimum\fP \fIminimum-size\fP"
>  Minimum contiguous free range to discard, in bytes. (This value is internally
>  rounded up to a multiple of the filesystem block size.)  Free ranges smaller
> -than this will be ignored.  By increasing this value, the fstrim operation
> -will complete more quickly for filesystems with badly fragmented freespace,
> -although not all blocks will be discarded.  The default value is zero,
> -discarding every free block.
> +than this will be ignored and kernel shall return modified value(fstrim_range.minlen)

Overly long line, and perhaps there should be a space between "value"
and "(fstrim_range.minlen)"?

> +to userspace.

What is the modified value?  You might as well say that fitrim will
adjust the minimum if it's smaller than the device's minimum, and report
that back to userspace.

> By increasing this value, the fstrim operation will complete
> +more quickly for filesystems with badly fragmented freespace, although not
> +all blocks will be discarded.  The default value is zero, discarding every free block.

I prefer the practice of starting each sentence in the manpage source on
a new line so that the diff only reflects changes to actual content (and
not just reflowing of the text)... but the sys-utils maintainers clearly
don't employ that convention so I guess this is ok. :)

Thanks for putting together the documentation update.
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

>  .IP "\fB\-v, \-\-verbose\fP"
>  Verbose execution.  With this option
>  .B fstrim
> -- 
> 2.21.0
>