Re: [PATCH] ext4: avoid buffer/folio lock inversion in __ext4_get_inode_loc()

[ThangNN99]

Hi Jan,

Yes, your understanding is correct: with foliosize == blocksize the
itable block and the bitmap block can never share a folio, so the two
lock orders can't overlap. It's only once foliosize > blocksize that
the itable block being written back can land in the same folio as the
bitmap block being probed, opening the window for the deadlock.

Thanks for the clearer write-up of the two lock orders, I've folded it
into the v2 changelog, along with your Reviewed-by tag and the
Assisted-by: LLM tag in place of the previous Co-Authored-By line.

Agreed on the broader concern -- sb_getblk() called while holding
another buffer locked is a general hazard, not specific to this one
call site. I don't have another confirmed instance yet; happy to help
grep for more if useful, but wanted to get this one fix out first
rather than block it on a wider audit.

Sending v2 now.

Thanks,
Thang