On 26.02.25 15:03, Matthew Wilcox wrote:
On Wed, Feb 26, 2025 at 06:48:15AM -0500, Brian Geffon wrote:
When handling faults for anon shmem finish_fault() will attempt to install
ptes for the entire folio. Unfortunately if it encounters a single
non-pte_none entry in that range it will bail, even if the pte that
triggered the fault is still pte_none. When this situation happens the
fault will be retried endlessly never making forward progress.
This patch fixes this behavior and if it detects that a pte in the range
is not pte_none it will fall back to setting just the pte for the
address that triggered the fault.
Surely there's a similar problem in do_anonymous_page()?
I recall we handle it in there correctly the last time I stared at it.
We check pte_none to decide which folio size we can allocate (including
basing the decision on other factors like VMA etc), and after retaking
the PTL, we recheck vmf_pte_changed / pte_range_none() to make sure
there were no races.
--
Cheers,
David / dhildenb
