[Crash-utility] [PATCH 1/1] CLI list command, print deep structure members

[Alexandr Terekhov]

On Tue, Apr 28, 2015 at 09:44:43AM -0400, Dave Anderson wrote:
> ----- Original Message -----
> > ----- Original Message -----
> > > Hi Dave,
> > > 
> > > I found it useful to be able listing structure's fields which are resided
> > > deeper than the first level:
> > > 
> > > crash> list super_block.s_list -s
> > > super_block.s_id,s_dquot.info[1].dqi_dirty_list,s_dquot.dqonoff_mutex.count.counter
> > > -H 0xc0a9c800
> > > de805c00
> > > s_id =
> > > "sysfs\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000",
> > > s_dquot.info[1].dqi_dirty_list = {
> > >   next = 0x0,
> > >   prev = 0x0
> > > },
> > > s_dquot.dqonoff_mutex.count.counter = 1
> > > de805800
> > > s_id =
> > > "rootfs\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000",
> > > s_dquot.info[1].dqi_dirty_list = {
> > >   next = 0x0,
> > >   prev = 0x0
> > > },
> > > s_dquot.dqonoff_mutex.count.counter = 1
> > > 
> > > Here is a draft patch which contains corresponding logic.
> > > I will appreciate your comments and suggestions.
> > > 
> > > Best regards,
> > > Alexandr
> > 
> > Hi Alexandr,
> > 
> > This looks quite useful.
> > 
> > I haven't looked at the details, but this kind of change modifies an a critical
> > area of usage that I cannot risk breaking.
> > 
> > To prevent any kind of possible regression/breakage or other unexpected behavior,
> > would it be possible to call parse_for_member_new() *only* if it is required?
> > In other words, if the commented-out MEMBER_EXISTS() call fails, then you could
> > set a flag to force it to attempt parse_for_member_new().  Otherwise, it could
> > continue to use the older/simpler parse_for_member() function.

Sounds reasonable. Will do.

> > I'll dig into the patch later, test it out, etc., and it's entirely possible
> > that I'll change my mind, but paranoia forces me to err on the side of caution.
> > 
> > Dave
>  
> Another issue that comes to mind is that there are several other instances
> in the crash utility command set besides the "list" command that specify 
> arguments that can be expressed in the "struct.member" format.  
> 
> By any chance, did you also attempt to fit this capability into the "struct"
> command itself?  And then there's also "tree", "task -R", "waitq", etc.

Haven't seen these commands before, will check. 
However I've found some issue while testing, so please wait with review
until I send fixed version.

Thank you,
Alexandr.