[#264] Zero pad the hexadecimal pid in the backup temporary file name to keep its length at 4-bytes even if the process_id is less than 2**24

[nars1]

No description provided.

[estess]

Does it matter that we might be truncating a pid here? PIDs are usually < 32K but the pid_t itself is an int and I thought there was a configuration option on the Linux kernel to widen the used PID field once storage passed a certain point or some such thing - can't remember. Anyway, should this be 8x instead of 4x to properly represent a 32 bit value?

[nars1]

Good catch. I forgot that hex digits are twice the byte length so it should be 8x instead of 4x. Will take care of that.

[ksbhaskar]

On 06/01/2018 09:58 AM, Steven E. Estes wrote: ***@***.**** commented on this pull request. ------------------------------------------------------------------------ In sr_port/mupip_backup.c <#269 (comment)>: > @@ -610,8 +610,12 @@ void mupip_backup(void) mubclnup(rptr, need_to_del_tempfile); mupip_exit(ustatus); } - /* Creating temp filename here. Check if we have the required space. */ - nbytes = SNPRINTF(tempfilename, SIZEOF(tempfilename), "%.*s/%.*s_%4x_XXXXXX", + /* Creating temp filename here. Check if we have the required space. + * Use %04x (instead of %x) for process_id to ensure we have 4 bytes always even if process_id + * is a small number (< 2**24 etc.) and is 0-filled on the left if needed. Makes the length + * deterministic instead of being dependent on the process_id. + */ + nbytes = SNPRINTF(tempfilename, SIZEOF(tempfilename), "%.*s/%.*s_%04x_XXXXXX", Does it matter that we might be truncating a pid here? PIDs are /usually/ < 32K but the pid_t itself is an int and I thought there was a configuration option on the Linux kernel to widen the used PID field once storage passed a certain point or some such thing - can't remember. Anyway, should this be 8x instead of 4x to properly represent a 32 bit value?

[KSB] From https://elixir.bootlin.com/linux/v4.16.13/source/include/linux/threads.h /* * A maximum of 4 million PIDs should be enough for a while. * [NOTE: PID/TIDs are limited to 2^29 ~= 500+ million, see futex.h.] */ #define PID_MAX_LIMIT (CONFIG_BASE_SMALL ? PAGE_SIZE * 8 : \ (sizeof(long) > 4 ? 4 * 1024 * 1024 : PID_MAX_DEFAULT)) – Bhaskar

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[nars1]

For the record. Even though this pull request identifies the issue # as #264, it actually fixes #267.