Ocfs2 devel - Dec 2015 - [PATCH v2 0/4] Add online file check feature

Hi Greg,

>>> 
> On Wed, Dec 02, 2015 at 07:05:27PM -0700, Gang He wrote:
>> Hello Pavel,
>> 
>> 
>> 
>> >>> 
>> > On Wed 2015-10-28 14:25:57, Gang He wrote:
>> >> When there are errors in the ocfs2 filesystem,
>> >> they are usually accompanied by the inode number which caused
the error.
>> >> This inode number would be the input to fixing the file.
>> >> One of these options could be considered:
>> >> A file in the sys filesytem which would accept inode numbers.
>> >> This could be used to communication back what has to be fixed
or is fixed.
>> >> You could write:
>> >> $# echo "CHECK <inode>" >
/sys/fs/ocfs2/devname/filecheck
>> >> or
>> >> $# echo "FIX <inode>" >
/sys/fs/ocfs2/devname/filecheck
>> >> 
>> > 
>> > Are you sure this is reasonable interface? I mean.... sysfs is
>> > supposed to be one value per file. And I don't think its
suitable for
>> > running commands.
>> Usually, the corrupted file (inode) should be rarely encountered for
OCFS2
> file system, then
>> lots of commands are executed via this interface with high performance
is
> not expected by us.
>> Second, after online file check is added, we also plan to add a mount
option
> "error=fix", that means
>> the file system can fix these errors automatically without a manual
command
> triggering.
> 
> It's not a "performance" issue, it's a "sysfs files
only have one value"
> type thing.  Have two files, "inode_fix" and
"inode_check" and then just
> write the inode into them, no need to have a "verb <inode>"
type parser.
Current, we have three functional items "check, fix and set", in the
future, maybe we can add more item.
Then, for each functional item, we need to create a sys file and add related
code (actual some code is duplicated),
I prefer to one sys file to handle multiple sub-commands.

Thanks
Gang
> 
> thanks,
> 
> greg k-h

On Fri 2015-12-04 01:36:21, Gang He wrote:
> Hi Greg,
> 
> 
> >>> 
> > On Wed, Dec 02, 2015 at 07:05:27PM -0700, Gang He wrote:
> >> Hello Pavel,
> >> 
> >> 
> >> 
> >> >>> 
> >> > On Wed 2015-10-28 14:25:57, Gang He wrote:
> >> >> When there are errors in the ocfs2 filesystem,
> >> >> they are usually accompanied by the inode number which
caused the error.
> >> >> This inode number would be the input to fixing the file.
> >> >> One of these options could be considered:
> >> >> A file in the sys filesytem which would accept inode
numbers.
> >> >> This could be used to communication back what has to be
fixed or is fixed.
> >> >> You could write:
> >> >> $# echo "CHECK <inode>" >
/sys/fs/ocfs2/devname/filecheck
> >> >> or
> >> >> $# echo "FIX <inode>" >
/sys/fs/ocfs2/devname/filecheck
> >> >> 
> >> > 
> >> > Are you sure this is reasonable interface? I mean.... sysfs
is
> >> > supposed to be one value per file. And I don't think its
suitable for
> >> > running commands.
> >> Usually, the corrupted file (inode) should be rarely encountered
for OCFS2
> > file system, then
> >> lots of commands are executed via this interface with high
performance is
> > not expected by us.
> >> Second, after online file check is added, we also plan to add a
mount option
> > "error=fix", that means
> >> the file system can fix these errors automatically without a
manual command
> > triggering.
> > 
> > It's not a "performance" issue, it's a "sysfs
files only have one value"
> > type thing.  Have two files, "inode_fix" and
"inode_check" and then just
> > write the inode into them, no need to have a "verb
<inode>" type parser.
> Current, we have three functional items "check, fix and set", in
the future, maybe we can add more item.
> Then, for each functional item, we need to create a sys file and add
related code (actual some code is duplicated),
> I prefer to one sys file to handle multiple sub-commands.
And we prefer not to have your code in tree.

Please design some reasonable interface. Abusing sysfs for this is not
right.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures)
http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

On Fri, Dec 04, 2015 at 01:36:21AM -0700, Gang He wrote:
> Hi Greg,
> 
> 
> >>> 
> > On Wed, Dec 02, 2015 at 07:05:27PM -0700, Gang He wrote:
> >> Hello Pavel,
> >> 
> >> 
> >> 
> >> >>> 
> >> > On Wed 2015-10-28 14:25:57, Gang He wrote:
> >> >> When there are errors in the ocfs2 filesystem,
> >> >> they are usually accompanied by the inode number which
caused the error.
> >> >> This inode number would be the input to fixing the file.
> >> >> One of these options could be considered:
> >> >> A file in the sys filesytem which would accept inode
numbers.
> >> >> This could be used to communication back what has to be
fixed or is fixed.
> >> >> You could write:
> >> >> $# echo "CHECK <inode>" >
/sys/fs/ocfs2/devname/filecheck
> >> >> or
> >> >> $# echo "FIX <inode>" >
/sys/fs/ocfs2/devname/filecheck
> >> >> 
> >> > 
> >> > Are you sure this is reasonable interface? I mean.... sysfs
is
> >> > supposed to be one value per file. And I don't think its
suitable for
> >> > running commands.
> >> Usually, the corrupted file (inode) should be rarely encountered
for OCFS2
> > file system, then
> >> lots of commands are executed via this interface with high
performance is
> > not expected by us.
> >> Second, after online file check is added, we also plan to add a
mount option
> > "error=fix", that means
> >> the file system can fix these errors automatically without a
manual command
> > triggering.
> > 
> > It's not a "performance" issue, it's a "sysfs
files only have one value"
> > type thing.  Have two files, "inode_fix" and
"inode_check" and then just
> > write the inode into them, no need to have a "verb
<inode>" type parser.
> Current, we have three functional items "check, fix and set", in
the future, maybe we can add more item.
> Then, for each functional item, we need to create a sys file and add
related code (actual some code is duplicated),
> I prefer to one sys file to handle multiple sub-commands.
No, sorry, that is not how sysfs works.  Please use individual files,
again, sysfs is "one value per file" you should never have to write a
"parser" for a sysfs file either reading, or writing to it.

If you need additional things in the future, great, add new sysfs files,
that makes it the easiest way for your userspace tools to be able to
determine if that feature is present in the kernel or not, it does not
have to write a command that it doesn't know if the kernel can handle or
not.

thanks,

greg k-h