[PATCH netfs v1 0/2] preserve prepare_write errno across write reissue

[Iván Ezequiel Rodriguez]

cifs (and others) may fail in prepare_write() with
netfs_prepare_write_failed() before write_retry calls
netfs_reissue_write().  Since 82e8885bd763, reissue clears
subreq->error to 0 for a clean I/O retry, so a FAILED subreq is
terminated with 0.  The collector then does mapping_set_error(0),
which is a no-op — writeback errno is lost (not an infinite retry).

Patch 1 skips that clear when FAILED is already set.
Patch 2 adds a KUnit stub test: FAIL unpatched, PASS patched.

  ./tools/testing/kunit/kunit.py run --kunitconfig=fs/netfs/.kunitconfig \
	netfs_reissue_write*

No prior lore report found for this interaction; surfaces on top of
Shyam's NEED_RETRY change.

Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: Paulo Alcantara <pc@xxxxxxxxxxxxx>
Cc: Shyam Prasad N <sprasad@xxxxxxxxxxxxx>
Cc: Steve French <stfrench@xxxxxxxxxxxxx>
Cc: netfs@xxxxxxxxxxxxxxx
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Cc: linux-cifs@xxxxxxxxxxxxxxx

Iván Ezequiel Rodriguez (2):
  netfs: preserve prepare_write errno on reissue
  netfs: add KUnit coverage for reissue prepare_write errno

 fs/netfs/.kunitconfig          |  3 ++
 fs/netfs/Kconfig               |  9 +++++
 fs/netfs/Makefile              |  2 +
 fs/netfs/write_collect.c       |  4 ++
 fs/netfs/write_issue.c         |  4 +-
 fs/netfs/write_reissue_kunit.c | 73 ++++++++++++++++++++++++++++++++++
 6 files changed, 94 insertions(+), 1 deletion(-)
 create mode 100644 fs/netfs/.kunitconfig
 create mode 100644 fs/netfs/write_reissue_kunit.c

-- 
2.43.0