mdstat_ent handling rework

[mtkaczyk]

No functional changes, just a follow-up of previous actions with a goal of decentralizing mdadm.

[Copilot]

Pull request overview

This PR refactors /proc/mdstat parsing and related helpers by moving the mdstat_ent API out of mdadm.h into a dedicated header (mdstat.h), and centralizing the "external:" prefix into a shared constants header (md_common.h). The intent aligns with the stated goal of decentralizing mdadm internals without functional changes.

Changes:

• Introduces mdstat.h (mdstat API/types) and md_common.h (shared md-driver string constants).
• Removes mdstat_ent and mdstat function declarations from mdadm.h, updating call sites to include mdstat.h.
• Replaces hard-coded "external:" and numeric offsets with MD_EXTERNAL_PREFIX / MD_EXTERNAL_PREFIX_LEN in multiple parsing/formatting paths, and relocates is_subarray_active() into mdstat.c.

Reviewed changes

Copilot reviewed 22 out of 22 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
util.c	Removes is_subarray_active() implementation (moved to mdstat module).
sysfs.c	Uses shared "external:" prefix macros when parsing/writing sysfs metadata version.
super-intel.c	Updates external-metadata parsing offsets to use MD_EXTERNAL_PREFIX_LEN; adds mdstat.h include.
msg.c	Adds mdstat.h include for mdstat types/helpers.
mdstat.h	New header exposing mdstat_ent type and mdstat helper APIs.
mdstat.c	Includes mdstat.h, uses shared prefix macros, and hosts is_subarray_active().
mdopen.c	Adds mdstat.h include for mdstat types/helpers.
mdmonitor.c	Adds mdstat.h include and updates external-metadata offsets to MD_EXTERNAL_PREFIX_LEN.
mdmon.h	Removes mdstat declarations now owned by mdstat.h.
mdmon.c	Adds mdstat.h include for mdstat types/helpers.
mdadm.h	Removes mdstat_ent struct and mdstat-related declarations and inline helper.
mdadm.c	Adds mdstat.h include for mdstat types/helpers.
md_common.h	New header centralizing shared md-driver constants (e.g., MD_EXTERNAL_PREFIX).
mapfile.c	Adds mdstat.h include for mdstat types/helpers.
managemon.c	Adds mdstat.h include for mdstat types/helpers.
Manage.c	Adds mdstat.h include and uses MD_EXTERNAL_PREFIX for metadata version composition.
Kill.c	Adds mdstat.h include for is_subarray_active() usage.
Incremental.c	Adds mdstat.h include for mdstat types/helpers.
Grow.c	Adds mdstat.h include and updates external-metadata offset usage.
Detail.c	Adds mdstat.h include and updates external-metadata parsing to use shared prefix macros.
config.c	Adds mdstat.h include for mdstat types/helpers.
Assemble.c	Adds mdstat.h include and updates external-metadata offset usage.

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[bkucman]

Hi, thank you for your patch.

there are still two more spot with "external:", you could also use define, unless you think that's overkill.

mdadm.c:1857
int member = e->metadata_version &&
strncmp(e->metadata_version,
"external:/", 10) == 0;

monitor.c:495
if (strncmp(buf, "external:-", 10) == 0) {

[mtkaczyk]

there are still two more spot with "external:", you could also use define, unless you think that's overkill.

lets proceed with this smaller rework. What you are asking is complete rework of how to set and read the version which I don't have good concept yet.

Noted this as a another thing to rework.