Messages in this thread |  | | | Date | Tue, 07 Mar 2006 10:21:25 +0300 | | From | Kirill Korotaev <> | | Subject | Re: [PATCH] Busy inodes after unmount, be more verbose in generic_shutdown_super |
>>No, it looks as it is not :( >>Have you noticed my comment about "count" argument to prune_dcache()? >>For example, prune_dcache() is called from shrink_dcache_parent() which >>is called in many places and not all of them have PF_MEMALLOC or >>s_umount semaphore for write. But prune_dcache() doesn't care for super >>blocks etc. It simply shrinks N dentries which are found _first_. >> >>So the condition: >>+ if ((current->flags & PF_MEMALLOC) && >>+ !(ret = down_read_trylock(&s->s_umount))) { >>is not always true when the race occurs, as PF_MEMALLOC is not always set. > > > I understand your comment about shrink_dcache_parent() being called > from several places. prune_one_dentry() would eventually dput the parent, > but unmount would go ahead and unmount the filesystem before the > dput of the parent could happen. exactly.
> Given that background, I thought our main concern was with respect to > unmount. The race was between shrink_dcache_parent() (called from unmount) > and shrink_dcache_memory() (called from the allocator), hence the fix > for the race condition. Partial fix doesn't make much sense from my point of view.
> I just noticied that 2.6.16-rc* now seems to have drop_slab() where > PF_MEMALLOC is not set. So, we can still race with my fix if there > if /proc/sys/vm/drop_caches is written to and unmount is done in parallel. > > A simple hack would be to set PF_MEMALLOC in drop_slab(), but I do not > think it is a good idea. Yeah, playing with PF_MEMALLOC can be not so good idea :/ And as it doesn't help in other cases it looks unpromising...
>>>Have you had any other feedback on this? >>here it is :) > Thanks for your detailed feedback Sorry, that I did it too late :/
Thanks, Kirill
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