Re: port binary dumping core on recent head in poudriere [tmpfs corruptions involving blocks of zeros that should not be all zeros]

On Tue, Nov 26, 2024 at 01:58:19PM +0100, Dimitry Andric wrote:
> On 26 Nov 2024, at 13:32, Dimitry Andric <dim@FreeBSD.org> wrote:
> > 
> > On 26 Nov 2024, at 11:19, Dag-Erling Smørgrav <des@FreeBSD.org> wrote:
> >> 
> >> Mark Millard <marklmi@yahoo.com> writes:
> >>> From inside a bulk -i where I did a manual make command
> >>> after it built and installed libsass.so.1.0.0 . The
> >>> manual make produced a /wrkdirs/ :
> >>> [...]
> >>> So the original creation looks okay. But . . .
> >>> [...]
> >>> So: The later, staged copy is a bad copy. Both are in the
> >>> tmpfs. So copying to the staging area makes a corrupted
> >>> copy inside the same tmpfs. After that, further copies of
> >>> staging's bad copy can be expected to be messed up.
> >> 
> >> This and the fact that it happens on 14 and 15 but not on 13 strongly
> >> suggests an issue wth `copy_file_range(2)`, since `install(1)` in 14 and
> >> 15 (but not in 13) now uses `copy_file_range(2)` if at all possible.
> >> 
> >> My educated guess is that hole detection doesn't work reliably for files
> >> that have had holes filled while memory-mapped, so `copy_file_range(2)`
> >> thinks there is a hole where there isn't one and skips some of the data
> >> when `install(1)` uses it to copy the library from `${WRKSRC}` to
> >> `${STAGEDIR}`.  This may or may not be specific to tmpfs.
> >> 
> >> You may want to try applying the attached patch to your FreeBSD 14 and
> >> 15 jails.  It prevents `cp(1)` and `install(1)` from trying to use
> >> `copy_file_range(2)`.
> > 
> > Yes, tmpfs is indeed the culprit (or at least involved). I have had USE_TMPFS=localbase in my poudriere.conf for a long time, since otherwise my build machine would run out of memory very quickly, so I didn't encounter any issues.
> > 
> > Now I changed it to USE_TMPFS=yes, rebuilt only textproc/libsass and textproc/sassc, and then after reinstalling those packages:
> > 
> > $ /usr/local/bin/sassc
> > Segmentation fault
> 
> And after applying Dag-Erling's patch to disable copy_file_range for cp and install, it works correctly again.

So indeed there might be an issue in tmpfs seeking for data.  Could you try
the following?

commit f4b848946a131dab260b44eab2cfabceb82bee0c
Author: Konstantin Belousov <kib@FreeBSD.org>
Date:   Tue Nov 26 15:34:56 2024 +0200

    tmpfs: do not skip pages searching for data
    
    If the iterator finds invalid page at the requested pindex in
    swap_pager_seek_data(), the current code only looks at the swap blocks
    to search for data.  This is not correct, valid pages may appear at the
    higher indexes still.

diff --git a/sys/vm/swap_pager.c b/sys/vm/swap_pager.c
index db925f4ae7f6..390b2c10d680 100644
--- a/sys/vm/swap_pager.c
+++ b/sys/vm/swap_pager.c
@@ -2503,12 +2503,9 @@ swap_pager_seek_data(vm_object_t object, vm_pindex_t pindex)
 	VM_OBJECT_ASSERT_RLOCKED(object);
 	vm_page_iter_init(&pages, object);
 	m = vm_page_iter_lookup_ge(&pages, pindex);
-	if (m != NULL) {
-		if (!vm_page_any_valid(m))
-			m = NULL;
-		else if (pages.index == pindex)
-			return (pages.index);
-	}
+	if (m != NULL && pages.index == pindex)
+		return (pages.index);
+
 	swblk_iter_init_only(&blks, object);
 	swap_index = swap_pager_iter_find_least(&blks, pindex);
 	if (swap_index == pindex)