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geom: disk_alloc_nowait will allocate a disk structure w/o sleeping
AbandonedPublic

Authored by imp on Mar 9 2021, 8:29 PM.

Details

Reviewers
kevans
glebius
ken
mav
scottl
phk
Group Reviewers
manpages
Summary

disk_alloc_nowait is just like disk_alloc, but won't wait for memory and may
return NULL. It's for drivers that need to create a disk from a non-sleepable
context.

Diff Detail

Repository
rS FreeBSD src repository - subversion
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Lint Passed
Unit
No Test Coverage
Build Status
Buildable 37707
Build 34596: arc lint + arc unit

Event Timeline

imp requested review of this revision.Mar 9 2021, 8:29 PM

I would probably just have added the flags argument to disk_alloc()...

Otherwise no comments.

In D29162#653000, @phk wrote:

I would probably just have added the flags argument to disk_alloc()...

I thought about that, but opted for this route because I didn't want to change a 2 dozen other places in the tree. And I kinda wanted to be able to MFC these changes too...

On second thought, I'm going to abandon this approach and schedule the cam register routine into a taskqueue so we can sleep. There's no good retry mechanism here, and adding one would make things more complicated. We can switch to waiting for memory to have a more robust system with simpler code. This also matches at least some of the feedback I've received privately (thanks Chuck). I'll post that review when I have it done.