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WhUQrLN3vFPLxYJbBi9FDXEN60IfGGtu8QgN+86QRzctojTBMrS0okvqFd4lF5bYS7G06ZV+Xtl BqY58521Xy514J+nxm7MWgW1HXdmHaWs0rHIWICM3r097utEF+IoQGDcMJ0v4oKDJQ8rLh2Y2kP 3PGBPv0w8nPWDcOTFzu7MxDbIwEl343DeMVWzcgFqifW38AepJVTSoP6W/QFCLeq07FBbGekX5m CAe9nZQH5EvHIAdR6acquV7fltAEiA== X-Proofpoint-GUID: 7-vwkfhXPuVFUz-6iUSxky14OzsvHTmc X-Proofpoint-ORIG-GUID: 7-vwkfhXPuVFUz-6iUSxky14OzsvHTmc X-Authority-Analysis: v=2.4 cv=Rdydyltv c=1 sm=1 tr=0 ts=691e0983 cx=c_pps a=XiAAW1AwiKB2Y8Wsi+sD2Q==:117 a=XiAAW1AwiKB2Y8Wsi+sD2Q==:17 a=6eWqkTHjU83fiwn7nKZWdM+Sl24=:19 a=z/mQ4Ysz8XfWz/Q5cLBRGdckG28=:19 a=lCpzRmAYbLLaTzLvsPZ7Mbvzbb8=:19 a=xqWC_Br6kY4A:10 a=kj9zAlcOel0A:10 a=6UeiqGixMTsA:10 a=GoEa3M9JfhUA:10 a=VkNPw1HP01LnGYTKEx00:22 a=zd2uoN0lAAAA:8 a=yPCof4ZbAAAA:8 a=HwWspdlWF_RiHFDO1V0A:9 a=CjuIK1q_8ugA:10 On Wed, Nov 19, 2025 at 03:55:29PM +0530, Garg, Shivank wrote: > > > 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. Yeah sorry I think I was being somehow blind to the fact that each dirty/writeback test has !is_shmem, esp. given I literally quote it there :) So err ignore me I think here haha > > Should I mention in the commit message that these changes are limited > to regular files and don't affect shmem? No that's fine. > > I'm not sure I fully understood your concern on shmem. Could you please elaborate? Yeah I think I just misread the code after a long day :P > > Thanks, > Shivank Cheers, Lorenzo > > > > > >> } 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 > >> >