Re: [PATCH] Monitor: improve check_one_sharer() for checking duplicated process

[Jes Sorensen <jes@trained-monkey.org>]

On 4/10/20 12:24 PM, Coly Li wrote:
> When running mdadm monitor with scan mode, only one autorebuild process
> is allowed. check_one_sharer() checks duplicated process by following
> steps,
> 1) Read autorebuild.pid file,
>    - if file does not exist, no duplicated process, go to 3).
>    - if file exists, continue to next step.
> 2) Read pid number from autorebuild.pid file, then check procfs pid
>    directory /proc/<PID>,
>    - if the directory does not exist, no duplicated process, go to 3)
>    - if the directory exists, print error message for duplicated process
>      and exit this mdadm.
> 3) Write current pid into autorebuild.pid file, continue to monitor in
>    scan mode.
> 
> The problem for the above step 2) is, if after system reboots and
> another different process happens to have exact same pid number which
> autorebuild.pid file records, check_one_sharer() will treat it as a
> duplicated mdadm process and returns error with message "Only one
> autorebuild process allowed in scan mode, aborting".
> 
> This patch tries to fix the above same-pid-but-different-process issue
> by one more step to check the process command name,
> 1) Read autorebuild.pid file
>    - if file does not exist, no duplicated process, go to 4).
>    - if file exists, continue to next step.
> 2) Read pid number from autorebuild.pid file, then check procfs file
>    comm with the specific pid directory /proc/<PID>/comm
>    - if the file does not exit, it means the directory /proc/<PID> does
>      not exist, go to 4)
>    - if the file exits, continue next step
> 3) Read process command name from /proc/<PIC>/comm, compare the command
>    name with "mdadm" process name,
>    - if not equal, no duplicated process, goto 4)
>    - if strings are equal, print error message for duplicated process
>      and exit this mdadm.
> 4) Write current pid into autorebuild.pid file, continue to monitor in
>    scan mode.
> 
> Now check_one_sharer() returns error for duplicated process only when
> the recorded pid from autorebuild.pid exists, and the process has exact
> same command name as "mdadm".
> 
> Reported-by: Shinkichi Yamazaki <shinkichi.yamazaki@suse.com>
> Signed-off-by: Coly Li <colyli@suse.de>
> ---
>  Monitor.c | 32 ++++++++++++++++++++------------
>  1 file changed, 20 insertions(+), 12 deletions(-)

Applied!

Thanks,
Jes