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cam: Drop periph lock when completing I/O with ENOMEM status

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When biofinish calls g_io_deliver with an error of ENOMEM, that kicks
off the slowdown protocol, forcing I/O to go through g_down rather than
be directly dispatch. One of the side effects is that the I/O is
resubmitted, so the start routines get called recursively, leading to a
recursive lock panic. Rather than make the periph lock recursive, drop
and reacquire the lock around such calls to biofinish.

For nda, this happens only when we can't allocate space to construct a
TRIM. For ada and da, this is only for certain ZONE operations.

Sponsored by:		Netflix
Reviewed by:		gallatin
Differential Revision:	https://reviews.freebsd.org/D45310
This commit is contained in:
Warner Losh 2024-05-24 08:32:04 -06:00
parent 6d83b38186
commit 99c14fb99f
3 changed files with 29 additions and 1 deletions
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9
sys/cam/ata/ata_da.c
View File

@ -2518,7 +2518,16 @@ adastart(struct cam_periph *periph, union ccb *start_ccb)
error = ada_zone_cmd(periph, start_ccb, bp, &queue_ccb);
if ((error != 0)
|| (queue_ccb == 0)) {
/*
* g_io_deliver will recurisvely call start
* routine for ENOMEM, so drop the periph
* lock to allow that recursion.
*/
if (error == ENOMEM)
cam_periph_unlock(periph);
biofinish(bp, NULL, error);
if (error == ENOMEM)
cam_periph_lock(periph);
xpt_release_ccb(start_ccb);
return;
}

10
sys/cam/nvme/nvme_da.c
View File

@ -1077,7 +1077,17 @@ ndastart(struct cam_periph *periph, union ccb *start_ccb)
trim = malloc(sizeof(*trim), M_NVMEDA, M_ZERO | M_NOWAIT);
if (trim == NULL) {
/*
* We have to drop the periph lock when
* returning ENOMEM. g_io_deliver treats these
* request differently and will recursively call
* the start routine which causes us to get into
* ndastrategy with the periph lock held,
* leading to a panic when its acquired again.
*/
cam_periph_unlock(periph);
biofinish(bp, NULL, ENOMEM);
cam_periph_lock(periph);
xpt_release_ccb(start_ccb);
ndaschedule(periph);
return;

11
sys/cam/scsi/scsi_da.c
View File

@ -3455,10 +3455,19 @@ dastart(struct cam_periph *periph, union ccb *start_ccb)
queue_ccb = 0;
error = da_zone_cmd(periph, start_ccb, bp,&queue_ccb);
error = da_zone_cmd(periph, start_ccb, bp, &queue_ccb);
if ((error != 0)
|| (queue_ccb == 0)) {
/*
* g_io_deliver will recurisvely call start
* routine for ENOMEM, so drop the periph
* lock to allow that recursion.
*/
if (error == ENOMEM)
cam_periph_unlock(periph);
biofinish(bp, NULL, error);
if (error == ENOMEM)
cam_periph_lock(periph);
xpt_release_ccb(start_ccb);
return;
}