Differential D31883

md: Add MD_MUSTDEALLOC support
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Authored by khng on Sep 8 2021, 6:41 PM.

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Reviewers

markj

Group Reviewers

manpages

Commits

rG3703c1888334: md: Add MD_MUSTDEALLOC support

Summary

This adds an option to detect if hole-punching is implemented by the
underlying file system. If this flag is set, and if the underlying file
system does not support hole-punching, md(4) fails BIO_DELETE requests
by returning unsupported.

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Repository

rG FreeBSD src repository

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Event Timeline

khng created this revision.Sep 8 2021, 6:41 PM

Herald added a reviewer: manpages. · View Herald TranscriptSep 8 2021, 6:41 PM

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khng requested review of this revision.Sep 8 2021, 6:41 PM

Harbormaster completed remote builds in B41433: Diff 94901.Sep 8 2021, 6:41 PM

Looks ok, but why not silently fall back to a default implementation for VOP_DEALLOCATE()?

sbin/mdconfig/mdconfig.8
290
sbin/mdconfig/mdconfig.c
93	Keep them sorted?

In D31883#719372, @markj wrote:

Looks ok, but why not silently fall back to a default implementation for VOP_DEALLOCATE()?

Eh, sorry, I misunderstood.

markj@'s suggestion

Harbormaster completed remote builds in B41435: Diff 94903.Sep 8 2021, 6:57 PM

markj added inline comments.Sep 8 2021, 7:01 PM

sbin/mdconfig/mdconfig.8
288	I think it could be a bit more clear: Start the description with "For .Cm vnode backed devices:" like other vnode-specific option descriptions. What happens if the file system does support hole-punching? What happens when autounmap is not specified and BIO_DELETE is received? Probably reference fspacectl.2 or just briefly describe the meaning of "hole-punching". "autounmap" also seems like a somewhat strange name to me. Is it named after something similar elsewhere?
sbin/mdconfig/mdconfig.c
221	These should be sorted.