[Bug 293198] zfs deadlock while copying many files, vfs_deleteextattr_dir-related?

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Newsgroups gmane.os.freebsd.devel.file-systems
Message-ID <[email protected]/bugzilla/>
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=293198

Konstantin Belousov <[email protected]> changed:

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--- Comment #6 from Konstantin Belousov <[email protected]> ---
(In reply to Peter Eriksson from comment #5)
I _suspect_ that was is happen there is lock recursion.

Note that the thread 105881 entered VOP_SETEXTATTR(), which (there is my guess)
taken the read lock, and after that it called VOP_OPEN(), which tries to take
the
read lock once more.

Meantime, the thread 104623 tries to take the same lock in the write mode, that
1. blocks further readers
2. blocks the thread itself because there is waiting writer

And the system deadlocks.  Either zfs should stop recursing into VFS on extattr
ops,
or the lock should be not taken recursively, or it should be changed to allow
readers to recurse even in presence of writers contenders.  The later would
mean
that writers cannot make progress if there is steady number of readers.

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