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Commit 6aa51072 authored Aug 15, 2014 by Paul Cassella Committed by Greg Kroah-Hartman Aug 17, 2014

staging/lustre/llite: Make sure ft_flags is valid



In ll_fault0, the 'fault' struct is mostly cleared before the call to
cl_io_loop, but ft_flags is not reset. It is ordinarily set by
the call to filemap_fault in vvp_io_kernel_fault, but if Lustre
returns before calling filemap_fault, it still has the old value of
ft_flags.

ll_fault0 will then consume the ft_flags field. If it has the
VM_FAULT_RETRY bit set, it will be used as ll_fault0() and
ll_fault()'s return value.

This is a problem when VM_FAULT_RETRY is in ft_flags:
When fault/filemap_fault return with that flag set, they have already
released the mmap semaphore, and do_page_fault does not need to
release it.
Incorrectly returning this flag from ll_fault means mmap_sem
is not upped in the kernel's do_page_fault().

In addition to clearing ft_flags, this patch does not use it unless
it is valid.  It's potentially misleading to return ft_flags in
"fault_ret" if ft_flags has not been set by filemap_fault.

This adds clarity, but does not change the current behavior:
When not valid, ft_flags is replaced by fault_ret, which is zero,
as is ft_flags when not set by filemap_fault.

Signed-off-by: Patrick Farrell <paf@cray.com>
Reviewed-on: http://review.whamcloud.com/10956
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-5291


Reviewed-by: Bobi Jam <bobijam@gmail.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 7591805a

drivers/staging/lustre/lustre/llite/llite_internal.h

+4 −0

Original line number	Original line	Diff line number	Diff line
	@@ -894,6 +894,10 @@ struct vvp_io {
	* fault API used bitflags for return code.		* fault API used bitflags for return code.
	*/		*/
	unsigned int ft_flags;		unsigned int ft_flags;
			/**
			* check that flags are from filemap_fault
			*/
			bool ft_flags_valid;
	} fault;		} fault;
	} fault;		} fault;
	} u;		} u;

drivers/staging/lustre/lustre/llite/llite_mmap.c

+7 −1

Original line number	Original line	Diff line number	Diff line
	@@ -310,10 +310,16 @@ static int ll_fault0(struct vm_area_struct vma, struct vm_fault vmf)
	vio->u.fault.ft_vma = vma;		vio->u.fault.ft_vma = vma;
	vio->u.fault.ft_vmpage = NULL;		vio->u.fault.ft_vmpage = NULL;
	vio->u.fault.fault.ft_vmf = vmf;		vio->u.fault.fault.ft_vmf = vmf;
			vio->u.fault.fault.ft_flags = 0;
			vio->u.fault.fault.ft_flags_valid = 0;

	result = cl_io_loop(env, io);		result = cl_io_loop(env, io);

			/* ft_flags are only valid if we reached
			* the call to filemap_fault */
			if (vio->u.fault.fault.ft_flags_valid)
	fault_ret = vio->u.fault.fault.ft_flags;		fault_ret = vio->u.fault.fault.ft_flags;

	vmpage = vio->u.fault.ft_vmpage;		vmpage = vio->u.fault.ft_vmpage;
	if (result != 0 && vmpage != NULL) {		if (result != 0 && vmpage != NULL) {
	page_cache_release(vmpage);		page_cache_release(vmpage);

drivers/staging/lustre/lustre/llite/vvp_io.c

+1 −0

Original line number	Original line	Diff line number	Diff line
	@@ -615,6 +615,7 @@ static int vvp_io_kernel_fault(struct vvp_fault_io *cfio)
	struct vm_fault *vmf = cfio->fault.ft_vmf;		struct vm_fault *vmf = cfio->fault.ft_vmf;

	cfio->fault.ft_flags = filemap_fault(cfio->ft_vma, vmf);		cfio->fault.ft_flags = filemap_fault(cfio->ft_vma, vmf);
			cfio->fault.ft_flags_valid = 1;

	if (vmf->page) {		if (vmf->page) {
	CDEBUG(D_PAGE,		CDEBUG(D_PAGE,