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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 11/10/2025 5:26 PM, Lorenzo Stoakes wrote: > Please, please, please send a cover letter when there's > 1 patch :) > > This 2/2 replying to 1/2 is a pain (not your fault that perhaps you're not aware > of typical mm series style but FYI :P) > Sure, will do this in V2 (posting today). > Also there is some tiny conflict on khugepaged.c in mm-new, but it's literally 1 > #include so probably nothing to worry about. > > On Mon, Nov 10, 2025 at 11:32:55AM +0000, Shivank Garg wrote: >> When MADV_COLLAPSE encounters dirty file-backed pages, it currently >> returns -EINVAL, this is misleading as EINVAL suggests invalid arguments, >> whereas dirty pages are a transient condition that may resolve on retry. >> >> Introduce SCAN_PAGE_DIRTY and map it to -EAGAIN. For khugepaged, this >> is harmless as it will revisit the range after async writeback completes. >> >> Signed-off-by: Shivank Garg > > With comments below addressed, LGTM so: > > Reviewed-by: Lorenzo Stoakes Thank you for the review. > >> --- >> include/trace/events/huge_memory.h | 3 ++- >> mm/khugepaged.c | 4 +++- >> 2 files changed, 5 insertions(+), 2 deletions(-) >> >> diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h >> index dd94d14a2427..9014a9bbe64c 100644 >> --- a/include/trace/events/huge_memory.h >> +++ b/include/trace/events/huge_memory.h >> @@ -38,7 +38,8 @@ >> EM( SCAN_PAGE_HAS_PRIVATE, "page_has_private") \ >> EM( SCAN_STORE_FAILED, "store_failed") \ >> EM( SCAN_COPY_MC, "copy_poisoned_page") \ >> - EMe(SCAN_PAGE_FILLED, "page_filled") >> + EM(SCAN_PAGE_FILLED, "page_filled") \ >> + EMe(SCAN_PAGE_DIRTY, "page_dirty") >> >> #undef EM >> #undef EMe >> diff --git a/mm/khugepaged.c b/mm/khugepaged.c >> index d08ed6eb9ce1..7df329c9c87d 100644 >> --- a/mm/khugepaged.c >> +++ b/mm/khugepaged.c >> @@ -60,6 +60,7 @@ enum scan_result { >> SCAN_STORE_FAILED, >> SCAN_COPY_MC, >> SCAN_PAGE_FILLED, >> + SCAN_PAGE_DIRTY, > > it feels like a lot to add a scan result for this, but I mean... probably > actually valid. > >> }; >> >> #define CREATE_TRACE_POINTS >> @@ -1967,7 +1968,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr, >> */ >> xas_unlock_irq(&xas); >> filemap_flush(mapping); >> - result = SCAN_FAIL; >> + result = SCAN_PAGE_DIRTY; >> goto xa_unlocked; > > Hmmm shmem dirty is going to be weird but we also have: > > if (!is_shmem && (folio_test_dirty(folio) || > folio_test_writeback(folio))) { > /* > * khugepaged only works on read-only fd, so this > * folio is dirty because it hasn't been flushed > * since first write. > */ > result = SCAN_FAIL; > goto out_unlock; > } > > It's weird though, why would we have writeback, surely handled by swap, and > won't it be like anon, i.e. pretty well always dirty? This comment seems > copy/pasta wrong. > > We do need to at least mention in commit message that shmem is explicitly > excluded. > Looking at the code, the dirty/writeback checks where I'm making changes are all in the !is_shmem branch, so it only affects regular files, not shmem. Should I mention in the commit message that these changes are limited to regular files and don't affect shmem? I'm not sure I fully understood your concern on shmem. Could you please elaborate? Thanks, Shivank > >> } else if (folio_test_writeback(folio)) { >> xas_unlock_irq(&xas); >> @@ -2747,6 +2748,7 @@ static int madvise_collapse_errno(enum scan_result r) >> case SCAN_PAGE_LRU: >> case SCAN_DEL_PAGE_LRU: >> case SCAN_PAGE_FILLED: >> + case SCAN_PAGE_DIRTY: >> return -EAGAIN; >> /* >> * Other: Trying again likely not to succeed / error intrinsic to >> -- >> 2.43.0 >>