Change vfs_busy to wait until an outcome of pending unmount operation is known and to retry or fail accordingly to that outcome. This fixes the problem with namespace traversing programs failing with random ENOENT errors if someone just happened to try to unmount that same filesystem at the same time.
Change vfs_busy to wait until an outcome of pending unmount
operation is known and to retry or fail accordingly to that
outcome. This fixes the problem with namespace traversing
programs failing with random ENOENT errors if someone just
happened to try to unmount that same filesystem at the same
time.

Reported by:	dhw
Reviewed by:	kib, attilio
Sponsored by:	Juniper Networks, Inc.

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