On 04/02/2015 07:27 PM, Raghavendra Bhat wrote:
On Thursday 02 April 2015 05:50 PM, Jeff Darcy wrote:
I think, crypt xlator should do a mem_put of local after doing
STACK_UNWIND
like other xlators which also use mem_get for local (such as AFR). I am
suspecting crypt not doing mem_put might be the reason for the bug
mentioned.
My understanding was that mem_put should be called automatically from
FRAME_DESTROY, which is itself called from STACK_DESTROY when the fop
completes (e.g. at FUSE or GFAPI). On the other hand, I see that AFR
and others call mem_put themselves, without zeroing the local pointer.
In my (possibly no longer relevant) experience, freeing local myself
without zeroing the pointer would lead to a double free, and I don't
see why that's not the case here. What am I missing?
As per my understanding, the xlators which get local by mem_get should
be doing below things in callback funtion just before unwinding:
1) save frame->local pointer (i.e. local = frame->local);
2) STACK_UNWIND
3) mem_put (local)
After STACK_UNWIND and before mem_put any reference to fd or inode or
dict that might be present in the local should be unrefed (also any
allocated resources that are present in local should be freed). So
mem_put is done at last. To avoid double free in FRAME_DESTROY,
frame->local is set to NULL before doing STACK_UNWIND.
I suspect not doing 1 of the above three operations (may be either 1st
or 3rd) in crypt xlator might be the reason for the bug.
I still don't understand why http://review.gluster.org/10109 is working.
Does anyone know the reason? How are you guys re-creating the crash? I
ran crypt.t but no crashes on my laptop. Could some one help me
re-create this issue.
Pranith
Regards,
Raghavendra Bhat
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