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Hold the reference count until the CCB is released

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When a disk disappears and the periph is invalidated, any I/Os that
are pending with the controller can cause a crash when they
complete. Move to holding the softc reference count taken in dastart()
until the I/O is complete rather than only until xpt_action()
returns. (This approach was suggested by Ken Merry.)

Sponsored by: Netflix
Submitted by: Chuck Silvers
Differential Revision: https://reviews.freebsd.org/D15435
This commit is contained in:
Warner Losh 2018-05-15 21:25:35 +00:00
parent 646fd30caf
commit 0eedd21317
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=333648
1 changed files with 6 additions and 5 deletions
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11
sys/cam/scsi/scsi_da.c
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@ -3300,7 +3300,6 @@ dastart(struct cam_periph *periph, union ccb *start_ccb)
cam_periph_unlock(periph);
xpt_action(start_ccb);
cam_periph_lock(periph);
softc->refcount--;
/* May have more work to do, so ensure we stay scheduled */
daschedule(periph);
@ -4443,13 +4442,15 @@ dadone(struct cam_periph *periph, union ccb *done_ccb)
softc->flags |= DA_FLAG_WAS_OTAG;
/*
* We need to call cam_iosched before we call biodone so that we
* don't measure any activity that happens in the completion
* routine, which in the case of sendfile can be quite
* extensive.
* We need to call cam_iosched before we call biodone so that we don't
* measure any activity that happens in the completion routine, which in
* the case of sendfile can be quite extensive. Release the periph
* refcount taken in dastart() for each CCB.
*/
cam_iosched_bio_complete(softc->cam_iosched, bp, done_ccb);
xpt_release_ccb(done_ccb);
KASSERT(softc->refcount >= 1, ("dadone softc %p refcount %d", softc, softc->refcount));
softc->refcount--;
if (state == DA_CCB_DELETE) {
TAILQ_HEAD(, bio) queue;