[PATCH v3 2/7] docs: submitting-patches: say which commit a Fixes tag names

[Sasha Levin]

The description of the Fixes: tag does not say which commit to name when
a later commit made an older bug reachable, or when more than one commit
introduced the same bug, and both questions come up regularly. The
commit that blame points at is also often one that only moved the code.

Say that the tag names the commit that introduced the bug, that the
commit that exposed it may get a second tag, and that each commit that
introduced the bug gets its own tag. Say that the tags tell the stable
team which trees need the fix, and that trees without any of the tagged
commits do not.

Link: https://lore.kernel.org/r/c3ce794d-1ac2-4ef3-9e5c-1e171bd77a89@xxxxxxxxxxxxx
Link: https://lore.kernel.org/r/20261013003535-mutt-send-email-mst@xxxxxxxxxx
Link: https://lore.kernel.org/r/atCI4q2HvqVXOag1@stanley.mountain
Assisted-by: LLM
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 Documentation/process/submitting-patches.rst | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/Documentation/process/submitting-patches.rst b/Documentation/process/submitting-patches.rst
index 7ae79452e1b46..7c4e3c8272d2a 100644
--- a/Documentation/process/submitting-patches.rst
+++ b/Documentation/process/submitting-patches.rst
@@ -608,6 +608,15 @@ which stable kernel versions should receive your fix. This is the preferred
 method for indicating a bug fixed by the patch. See :ref:`describe_changes`
 for more details.
 
+Name the commit that introduced the bug. ``git blame`` and ``git bisect`` can
+point at a commit that only moved the code, or that made an older bug
+reachable. If a later commit made an older bug reachable, name the commit that
+introduced the bug; a second Fixes: tag for the later commit is fine. If the
+same bug was introduced separately by more than one commit, add a Fixes: tag
+for each, but do not add tags for commits that are only suspected. The Fixes:
+tags tell the stable team which trees need the fix: those that contain one of
+the tagged commits. Trees that contain none of them do not need it.
+
 Note: Attaching a Fixes: tag does not subvert the stable kernel rules
 process nor the requirement to Cc: stable@xxxxxxxxxxxxxxx on all stable
 patch candidates. For more information, please read
-- 
2.53.0