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From: Lance Yang In-Reply-To: <20BA865A-1B69-48DA-BE12-9BFC6EA5A4CE@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 935994000A X-Stat-Signature: cjo4y5j4wm5obt3qi9ixw1q1upbenqsm X-Rspam-User: X-HE-Tag: 1776919679-699170 X-HE-Meta: U2FsdGVkX190WS4E3aNEhpjVUIRt8ga62rV+ghYYSmhZ9k76TWxnFRHW1pEim8EX7GFtQdyRueFrAhzrrOKxWnUns1lHVax2mxjP4Wc375qWhMsc3yy1WrgQVEje81rOnQYaslmygDgiM43KoM2d3BhlpBKvefAk7tqvRDM4ypfQxxBMpJ7kJ4XupnFCrO6XFGim8fN2PtpRb1L2meuMsQ8T3zHZ/cIJ4eDSkiFuGBg/aGLMUdpH8f7kRxXHxW5Z5HsWSkiRxXUg9y8PPW7nFvzOtc4HtZyShFRobf/xfBWTmLRPrL1JOYoGB5XVhJH1GDiQB8HdjLoZIZY2cJTKGw1q/gsbnLLjDPZRQ7WxB78VBJmxnN3+JfcmCQ5AM5d0pwMeY9PilNlOSqABSspjr99yK/mmoVA61lJUukQn9uOSjrpQ4GkKHlW9GboDY5HVT/ht5c3VGIRvASnN60Baz9GvIHOhCCZOuL5iePRKlHdiQ4Jovh4zqAGjM22tmGz6VV4MscWjWfCCuQkqapW0FQn7s0UDXv7O1M0UN3SyT0YIy44WUmkmWhshsk5ZtPZHKOugs042KHVVYI+jtggSCUKKYnx/htvUndEKf4KV0fPZtEUkGN2JsgFPEhkGMHp9Yf9AJ7UcRJ62TIZXm+YV31vyMXrtRawk0X+pl2q5yoyAUZFvbzjcmok+9pdzU8YnuY2cZrMoUAFC7l5O94f8lgHw/sdknfoXyluz3OXagMtze3njOJp3MGLrV/U+ZRQO9tUTTC8AaYDys72JUHKnsVrqxsJQZPJ+xquLhd1DaIvuH1bQiNrwCpm/CYZ3lxABgyW0+soFag5k6Db7z8dXTYqOeBw+EV1Ol67VoyI5vtqcLVUAzP6CvZlBibrMPKiba/RDt94taeRba6GMuyij9sZqAcjwNMlbzYa5570LqhvmQYqIKrtfjXxTEVpi3wsDaqJQ/BxRKD6XYfWvX0p G8BadoI/ WF91kWc6gZsbHdcgq+Y/Wc+Ix+BmtD+CgLr6DCRf2uHu85NW6X+5GlDyLL01Ovc88JOCLU8b38XI3HlnoXnTWrsDT1X3detykRJlRycLbmbPF7V6hUeZ4Lo9ab8I8CgItOJCHj9guaCR8OhzooXrmWFPMPvD6IN0eip6WzAFNrR1PkHvA2fAkDnHvB62Rfcp8gANuuT9k2r09ZNonh5tvC2D10Dcji8qq0sDs06E33sUY8Esl4CwrpWAf66BMWSWcxQgKkw/Gud4UFwM= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2026/4/23 10:51, Zi Yan wrote: > On 22 Apr 2026, at 22:43, Lance Yang wrote: > >> On Fri, Apr 17, 2026 at 10:44:18PM -0400, Zi Yan wrote: >>> collapse_file() requires FSes supporting large folio with at least >>> PMD_ORDER, so replace the READ_ONLY_THP_FOR_FS check with that. >>> MADV_COLLAPSE ignores shmem huge config, so exclude the check for shmem. >>> >>> While at it, replace VM_BUG_ON with VM_WARN_ON_ONCE. >>> >>> Add a helper function mapping_pmd_thp_support() for FSes supporting large >>> folio with at least PMD_ORDER. >>> >>> Signed-off-by: Zi Yan >>> --- >>> include/linux/pagemap.h | 10 ++++++++++ >>> mm/khugepaged.c | 5 +++-- >>> 2 files changed, 13 insertions(+), 2 deletions(-) >>> >>> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h >>> index ec442af3f886..c3cb1ec982cd 100644 >>> --- a/include/linux/pagemap.h >>> +++ b/include/linux/pagemap.h >>> @@ -524,6 +524,16 @@ static inline bool mapping_large_folio_support(const struct address_space *mappi >>> return mapping_max_folio_order(mapping) > 0; >>> } >>> >>> +static inline bool mapping_pmd_thp_support(const struct address_space *mapping) >>> +{ >>> + /* AS_FOLIO_ORDER is only reasonable for pagecache folios */ >>> + VM_WARN_ONCE((unsigned long)mapping & FOLIO_MAPPING_ANON, >>> + "Anonymous mapping always supports PMD THP"); >> >> Nit: afraid not, at least when running on architectures without PMD leaf >> entries ... >> >> Maybe better to say this helper is only meaningful for pagecache-backed >> mappings. Anonymous mappings should not reach here. > > Good suggestion. Will fix it. > >> >>> + >>> + return mapping_max_folio_order(mapping) >= PMD_ORDER; >>> +} >>> + >>> + >>> /* Return the maximum folio size for this pagecache mapping, in bytes. */ >>> static inline size_t mapping_max_folio_size(const struct address_space *mapping) >>> { >>> diff --git a/mm/khugepaged.c b/mm/khugepaged.c >>> index b8452dbdb043..3eb5d982d3d3 100644 >>> --- a/mm/khugepaged.c >>> +++ b/mm/khugepaged.c >>> @@ -1892,8 +1892,9 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr, >>> int nr_none = 0; >>> bool is_shmem = shmem_file(file); >>> >>> - VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem); >>> - VM_BUG_ON(start & (HPAGE_PMD_NR - 1)); >>> + /* MADV_COLLAPSE ignores shmem huge config, so do not check shmem */ >>> + VM_WARN_ON_ONCE(!is_shmem && !mapping_pmd_thp_support(mapping)); >> >> With [1], can we drop !is_shmem here as well? shmem would then always >> call mapping_set_large_folios(inode->i_mapping): >> >> ---8<--- >> diff --git a/mm/shmem.c b/mm/shmem.c >> index 4ecefe02881d..dafbea53b22d 100644 >> --- a/mm/shmem.c >> +++ b/mm/shmem.c >> @@ -3087,10 +3087,7 @@ static struct inode *__shmem_get_inode(struct mnt_idmap *idmap, >> cache_no_acl(inode); >> if (sbinfo->noswap) >> mapping_set_unevictable(inode->i_mapping); >> - >> - /* Don't consider 'deny' for emergencies and 'force' for testing */ >> - if (sbinfo->huge) >> - mapping_set_large_folios(inode->i_mapping); >> + mapping_set_large_folios(inode->i_mapping); >> >> switch (mode & S_IFMT) { >> default: >> -- >> >> But we can do that in a follow-up, once the revert lands :) > > Right. That would make this patchset depend on Baolin’s fix. A follow-up > patch is easier for managing these patches. I will add a TODO in the > comment, so that we will not forget. Thank you for the suggestion. OK. With the changes above, Reviewed-by: Lance Yang