On Mon, Mar 09, 2026 at 11:54:39AM +0000, Pratyush Yadav wrote: > From: "Pratyush Yadav (Google)" <[email protected]> > > When memory is added to a memfd via fallocate(), it does not get zeroed > immediately. This is tracked by the absence of the uptodate folio flag. > Initially, memfd preservation simply saved the folio flags at preserve > time. This led to a bug, where all writes to un-initialized fallocated > memory after preserve were lost after live update. This is fixed by > patch [0] (not in mainline as of writing this). > > Add a test that fallocates some memory in a memfd, preserves it, writes > to it. Then in stage 2 it verifies the written content is still present. > > [0] > https://lore.kernel.org/linux-mm/[email protected]/
Looks like it's already in mm-stable, so it's sha should be stable already. > Signed-off-by: Pratyush Yadav (Google) <[email protected]> > --- > .../testing/selftests/liveupdate/luo_memfd.c | 64 +++++++++++++++++++ > 1 file changed, 64 insertions(+) > > diff --git a/tools/testing/selftests/liveupdate/luo_memfd.c > b/tools/testing/selftests/liveupdate/luo_memfd.c > index 75f88101e7b5..dde3c78db50e 100644 > --- a/tools/testing/selftests/liveupdate/luo_memfd.c > +++ b/tools/testing/selftests/liveupdate/luo_memfd.c > @@ -43,6 +43,11 @@ > #define PRESERVED_MEMFD_TOKEN 1 > #define PRESERVED_BUFFER_SIZE SZ_1M > > +#define FALLOCATE_SESSION_NAME "fallocate_session" > +#define FALLOCATE_MEMFD_TOKEN 1 > +#define FALLOCATE_BUFFER_SIZE SZ_1M > +#define RANDOM_DATA_FILE_FALLOCATE "luo_random_data_fallocate.bin" FILESYSTEM_COPY_ or something like that? > + > #define LIVEUPDATE_DEV "/dev/liveupdate" > static int luo_fd = -1, stage; > > @@ -193,6 +198,65 @@ TEST(preserved_ops) > ASSERT_EQ(lseek(fd, 0, SEEK_END), PRESERVED_BUFFER_SIZE); > } > > +/* > + * Test that an fallocated memfd is preserved across live update and can be > + * written to after being preserved. > + */ > +TEST(fallocate_memfd) > +{ > + int fd, session; > + char *buffer; > + struct liveupdate_session_preserve_fd preserve_arg = { .size = > sizeof(preserve_arg) }; > + struct liveupdate_session_retrieve_fd retrieve_arg = { .size = > sizeof(retrieve_arg) }; > + > + buffer = malloc(FALLOCATE_BUFFER_SIZE); > + ASSERT_NE(buffer, NULL); > + > + switch (stage) { > + case 1: Functions again :) Reviewed-by: Mike Rapoport (Microsoft) <[email protected]> -- Sincerely yours, Mike.
