selftests/filesystems: check that a busy submount survives a synchronous umount

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Add a test for the shrinkable submounts of a synchronous umount:

- P shared, P1 a slave that is shared in turn, P2 its peer
- B on P/options with copies on P1 and P2, R on top of the copy in P2
- P with B moved below P1, R is the working directory
- umount(P1) slides R to where the copy of B is looked up

The umount fails with EBUSY and R stays mounted. Needs the tracefs
automount below debugfs for the shrinkable mounts.

Link: https://patch.msgid.link/20260930-work-mount-fixes-3-v1-3-be34c83956ae@kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

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Christian Brauner 2026-09-30 15:31:55 +02:00

parent 32bf924166

commit 520b5a15fc

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tools/testing/selftests/filesystems/umount_propagation/Makefile

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211

tools/testing/selftests/filesystems/umount_propagation/shrink_submounts_test.c

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