When collapse_file encounters dirty or writeback pages in file-backed mappings, it currently returns SCAN_FAIL which maps to -EINVAL. This is misleading as EINVAL suggests invalid arguments, whereas dirty/writeback pages represent transient conditions that may resolve on retry.
Introduce SCAN_PAGE_DIRTY_OR_WRITEBACK to cover both dirty and writeback states, mapping it to -EAGAIN. For MADV_COLLAPSE, this provides userspace with a clear signal that retry may succeed after writeback completes. For khugepaged, this is harmless as it will naturally revisit the range during periodic scans after async writeback completes. Reported-by: Branden Moore <[email protected]> Closes: https://lore.kernel.org/all/[email protected] Fixes: 34488399fa08 ("mm/madvise: add file and shmem support to MADV_COLLAPSE") Reviewed-by: Dev Jain <[email protected]> Reviewed-by: Lance Yang <[email protected]> Signed-off-by: Shivank Garg <[email protected]> --- include/trace/events/huge_memory.h | 3 ++- mm/khugepaged.c | 8 +++++--- 2 files changed, 7 insertions(+), 4 deletions(-) diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h index 4cde53b45a85..4e41bff31888 100644 --- a/include/trace/events/huge_memory.h +++ b/include/trace/events/huge_memory.h @@ -37,7 +37,8 @@ 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_OR_WRITEBACK, "page_dirty_or_writeback") #undef EM #undef EMe diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 97d1b2824386..219dfa2e523c 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -58,6 +58,7 @@ enum scan_result { SCAN_STORE_FAILED, SCAN_COPY_MC, SCAN_PAGE_FILLED, + SCAN_PAGE_DIRTY_OR_WRITEBACK, }; #define CREATE_TRACE_POINTS @@ -1967,11 +1968,11 @@ 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_OR_WRITEBACK; goto xa_unlocked; } else if (folio_test_writeback(folio)) { xas_unlock_irq(&xas); - result = SCAN_FAIL; + result = SCAN_PAGE_DIRTY_OR_WRITEBACK; goto xa_unlocked; } else if (folio_trylock(folio)) { folio_get(folio); @@ -2018,7 +2019,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr, * folio is dirty because it hasn't been flushed * since first write. */ - result = SCAN_FAIL; + result = SCAN_PAGE_DIRTY_OR_WRITEBACK; goto out_unlock; } @@ -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_OR_WRITEBACK: return -EAGAIN; /* * Other: Trying again likely not to succeed / error intrinsic to -- 2.43.0
