s390/dasd: Extend prepare_itcw() to support WRITE_FULL_TRACK

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prepare_itcw() builds the FCX prefix block (PFX + LRE) for track-mode
I/O. Extend it to handle DASD_ECKD_CCW_WRITE_FULL_TRACK.

WRITE_FULL_TRACK needs two extra bytes appended to the LRE for that
bitmask. The prefix block is a scratch buffer copied into the TCCB by
itcw_add_dcw(), so keep it on the stack (sized for the two extra bytes)
rather than allocating it: this runs in the writeback path and must not
depend on an allocation that can fail under memory pressure.

Reviewed-by: Jan Höppner <hoeppner@linux.ibm.com>
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
Link: https://patch.msgid.link/20260805111612.1285190-11-sth@linux.ibm.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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Stefan Haberland 2026-08-05 13:16:03 +02:00 • committed by Jens Axboe

parent 0569784929

commit 44f9bf4798

1 changed files with 51 additions and 13 deletions

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drivers/s390/block/dasd_eckd.c

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