Re: [PATCH v1 01/18] mm: allow for detecting underflows with page_mapcount() again
Matthew Wilcox <[email protected]>
| Newsgroups | gmane.linux.documentation,gmane.linux.kernel,gmane.linux.kernel.mm,gmane.linux.kernel.cgroups,gmane.linux.ports.sh.devel,gmane.linux.file-systems |
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| Message-ID | <[email protected]> |
On Tue, Apr 09, 2024 at 09:22:44PM +0200, David Hildenbrand wrote:
> Commit 53277bcf126d ("mm: support page_mapcount() on page_has_type()
> pages") made it impossible to detect mapcount underflows by treating
> any negative raw mapcount value as a mapcount of 0.
Yes, but I don't think this is the right place to check for underflow.
We should be checking for that on modification, not on read. I think
it's more important for page_mapcount() to be fast than a debugging aid.