On Jan 3, 2014, at 10:13 PM, Mindaugas Rasiukevicius <rm...@netbsd.org> wrote:

> "Juergen Hannken-Illjes" <hann...@netbsd.org> wrote:
>> Module Name: src
>> Committed By:        hannken
>> Date:                Fri Jan  3 09:53:12 UTC 2014
>> Modified Files:
>>      src/sys/fs/tmpfs: tmpfs_subr.c tmpfs_vnops.c
>> Log Message:
>> Fix a race where thread1 runs VOP_REMOVE() and gets preempted in
>> tmpfs_reclaim() before the call to tmpfs_free_node().  Thread2
>> runs VFS_FHTOVP() and gets a new vnode attached to the node thread1
>> is about to destroy.
>> Change tmpfs_alloc_node() to always assign non-zero generation number
>> and tmpfs_inactive() to set the generation number of unlinked nodes
>> to zero.
> Can you explain how does this help?  It still seems racy to me.

Please describe the race in more detail.  Tmpfs_fhtovp() will fail
as soon as an unlinked tmpfs node drops its last vnode reference.

> Why not just check for tn_links == 0 in tmpfs_fhtovp()?

Because it is ok as long as the corresponding vnode is open/referenced.

J. Hannken-Illjes - hann...@eis.cs.tu-bs.de - TU Braunschweig (Germany)

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