Re: find command trigger coredump

[Paul Eggert]

Thanks for the bug report archived at 
<https://lists.gnu.org/r/bug-gnulib/2020-04/msg00068.html>. What you appear to 
be saying is that the Gnulib fts NOSTAT_LEAF_OPTIMIZATION code is buggy when an 
XFS filesystem is mutating, and that your test case illustrates a mutating 
filesystem that can cause 'find' and 'du' to dump core because fts.c's 
tight-cycle check messes up its hash table.

I reproduced the bug on an XFS filesystem on Fedora 31 x86-64.

I worked around the bug by removing that optimization from Gnulib fts.c, by 
installing the attached patch. I expect that this optimization is obsolete 
nowadays, as XFS is now working and ReiserFS is either working, or is so 
unpopular that high performance for du and find is not that important for it.

I have the sneaking suspicion that we can now remove at least some of the 
special cases for AFS, CIFS, NFS, and /proc filesystems in the leaf_optimization 
subroutine. However, doing so would merely improve performance, so I resisted 
the temptation to make that change. I'll cc this message to other people who've 
touched the fts.c code to see whether they have any advice about that.

Thanks again for reporting the bug.

0001-fts-remove-NOSTAT_LEAF_OPTIMIZATION.patch
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