On 3/27/26 13:23, Lorenzo Stoakes (Oracle) wrote: > On Thu, Mar 26, 2026 at 09:42:48PM -0400, Zi Yan wrote: >> They are used by READ_ONLY_THP_FOR_FS to handle writes to FSes without >> large folio support, so that read-only THPs created in these FSes are not >> seen by the FSes when the underlying fd becomes writable. Now read-only PMD >> THPs only appear in a FS with large folio support and the supported orders >> include PMD_ORDRE. > > Typo: PMD_ORDRE -> PMD_ORDER > >> >> Signed-off-by: Zi Yan <[email protected]> > > This looks obviously-correct since this stuff wouldn't have been invoked for > large folio file systems before + they already had to handle it separately, > and > this function is only tied to CONFIG_READ_ONLY_THP_FOR_FS (+ a quick grep > suggests you didn't miss anything), so:
There could now be a race between collapsing and the file getting opened r/w. Are we sure that all code can really deal with that? IOW, "they already had to handle it separately" -- is that true? khugepaged would have never collapse in writable files, so I wonder if all code paths are prepared for that. -- Cheers, David
