Re: [LTP] [PATCH v2 3/5] swapon03: Try to swapon() as many files until it fails

Petr Vorel
2025-11-11T15:59:08Z

Hi Cyril,

> Hi!
> > is_swap_supported(TEST_FILE);
> > +
> > + swapfiles = SAFE_MMAP(NULL, sizeof(*swapfiles), PROT_READ | PROT_WRITE,
> > + MAP_SHARED | MAP_ANONYMOUS, -1, 0);
> > + *swapfiles = 0;
> > +
> > setup_swap();
> > }

> > static void cleanup(void)
> > {
> > - clean_swap();
> > + if (swapfiles) {
> > + clean_swap();
> > + SAFE_MUNMAP(swapfiles, sizeof(*swapfiles));
> > + }
> > }

First, thank you for your review!

> This gets complicated for no good reason since we run the setup code in the
> child.

If swapfiles is not mapped for some reason (can happen or "*swapfiles = 0" is
not run (that should not happen), then using *swapfiles leads to segfault.

*swapfiles is being used not only in SAFE_MUNMAP() here in cleanup(), but
also in clean_swap().

Also, this saves trying to deactivate swap files if they weren't activated.

And, unless "swapon03: Remove grep dependency" (the last commit) is accepted,
there is a corner case I found during debugging:

# ./swapon03 # quit early with ctrl+C => some swap partitions are left not being swapped off
...
Sending SIGKILL to test process...
tst_test.c:1909: TINFO: Killed the leftover descendant processes
tst_test.c:1918: TINFO: If you are running on slow machine, try exporting LTP_TIMEOUT_MUL > 1
tst_test.c:1920: TBROK: Test killed! (timeout?)

Summary:
passed 0
failed 0
broken 1
skipped 0
warnings 0
tst_device.c:417: TINFO: umount('mntpoint') failed with EBUSY, try 1...
tst_device.c:421: TINFO: Likely gvfsd-trash is probing newly mounted fs, kill it to speed up tests.
tst_device.c:417: TINFO: umount('mntpoint') failed with EBUSY, try 2...
tst_device.c:417: TINFO: umount('mntpoint') failed with EBUSY, try 3...
tst_device.c:417: TINFO: umount('mntpoint') failed with EBUSY, try 4...
tst_device.c:417: TINFO: umount('mntpoint') failed with EBUSY, try 5...
tst_device.c:417: TINFO: umount('mntpoint') failed with EBUSY, try 6...
tst_device.c:417: TINFO: umount('mntpoint') failed with EBUSY, try 7...
tst_device.c:417: TINFO: umount('mntpoint') failed with EBUSY, try 8...
tst_device.c:417: TINFO: umount('mntpoint') failed with EBUSY, try 9...
tst_device.c:417: TINFO: umount('mntpoint') failed with EBUSY, try 10...

Then following run tries to swapoff() partition left from previous run.

# ./swapon03
...
swapon03.c:80: TWARN: Failed to swapoff mntpoint/testswap

But the last commit fixes this problem.

Kind regards,
Petr