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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: 79u6jfd3hkssgr5jr4b8j4zheef6w7so X-Rspamd-Queue-Id: DB4FA40004 X-Rspamd-Server: rspam11 X-Rspam-User: X-HE-Tag: 1751361904-363913 X-HE-Meta: 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 7AGtQodr 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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 30.06.25 19:05, Lorenzo Stoakes wrote: > On Mon, Jun 30, 2025 at 02:59:50PM +0200, David Hildenbrand wrote: >> Let's factor it out, simplifying the calling code. >> >> The assumption is that flush_dcache_page() is not required for >> movable_ops pages: as documented for flush_dcache_folio(), it really >> only applies when the kernel wrote to pagecache pages / pages in >> highmem. movable_ops callbacks should be handling flushing >> caches if ever required. > > But we've enot changed this have we? The flush_dcache_folio() invocation seems > to happen the same way now as before? Did I miss something? I think, before this change we would have called it also for movable_ops pages if (rc == MIGRATEPAGE_SUCCESS) { if (__folio_test_movable(src)) { ... } ... if (likely(!folio_is_zone_device(dst))) flush_dcache_folio(dst); } Now, we no longer do that for movable_ops pages. For balloon pages, we're not copying anything, so we never possibly have to flush the dcache. For zsmalloc, we do the copy in zs_object_copy() through kmap_local. I think we could have HIGHMEM, so I wonder if we should just do a flush_dcache_page() in zs_object_copy(). At least, staring at highmem.h with memcpy_to_page(), it looks like that might be the right thing to do. So likely I'll add a patch before this one that will do the flush_dcache_page() in there. > >> >> Note that we can now change folio_mapping_flags() to folio_test_anon() >> to make it clearer, because movable_ops pages will never take that path. >> >> Reviewed-by: Zi Yan >> Signed-off-by: David Hildenbrand > > Have scrutinised this a lot and it seems correct to me, so: > > Reviewed-by: Lorenzo Stoakes > >> --- >> mm/migrate.c | 82 ++++++++++++++++++++++++++++------------------------ >> 1 file changed, 45 insertions(+), 37 deletions(-) >> >> diff --git a/mm/migrate.c b/mm/migrate.c >> index d97f7cd137e63..0898ddd2f661f 100644 >> --- a/mm/migrate.c >> +++ b/mm/migrate.c >> @@ -159,6 +159,45 @@ static void putback_movable_ops_page(struct page *page) >> folio_put(folio); >> } >> >> +/** >> + * migrate_movable_ops_page - migrate an isolated movable_ops page >> + * @page: The isolated page. >> + * >> + * Migrate an isolated movable_ops page. >> + * >> + * If the src page was already released by its owner, the src page is >> + * un-isolated (putback) and migration succeeds; the migration core will be the >> + * owner of both pages. >> + * >> + * If the src page was not released by its owner and the migration was >> + * successful, the owner of the src page and the dst page are swapped and >> + * the src page is un-isolated. >> + * >> + * If migration fails, the ownership stays unmodified and the src page >> + * remains isolated: migration may be retried later or the page can be putback. >> + * >> + * TODO: migration core will treat both pages as folios and lock them before >> + * this call to unlock them after this call. Further, the folio refcounts on >> + * src and dst are also released by migration core. These pages will not be >> + * folios in the future, so that must be reworked. >> + * >> + * Returns MIGRATEPAGE_SUCCESS on success, otherwise a negative error >> + * code. >> + */ > > Love these comments you're adding!! > >> +static int migrate_movable_ops_page(struct page *dst, struct page *src, >> + enum migrate_mode mode) >> +{ >> + int rc = MIGRATEPAGE_SUCCESS; > > Maybe worth asserting src, dst locking? We do have these sanity checks right now in move_to_new_folio() already. (next patch moves it further out) Not sure how reasonable these sanity checks are in these internal helpers: E.g., after we called move_to_new_folio() we will unlock both folios, which should blow up if the folios wouldn't be locked. -- Cheers, David / dhildenb