From: Paul Cassella <casse...@cray.com> 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 <p...@cray.com> Reviewed-on: http://review.whamcloud.com/10956 Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-5291 Reviewed-by: Bobi Jam <bobi...@gmail.com> Reviewed-by: Jinshan Xiong <jinshan.xi...@intel.com> Signed-off-by: Oleg Drokin <oleg.dro...@intel.com> --- drivers/staging/lustre/lustre/llite/llite_internal.h | 4 ++++ drivers/staging/lustre/lustre/llite/llite_mmap.c | 8 +++++++- drivers/staging/lustre/lustre/llite/vvp_io.c | 1 + 3 files changed, 12 insertions(+), 1 deletion(-) diff --git a/drivers/staging/lustre/lustre/llite/llite_internal.h b/drivers/staging/lustre/lustre/llite/llite_internal.h index 634ffa6..684405e 100644 --- a/drivers/staging/lustre/lustre/llite/llite_internal.h +++ b/drivers/staging/lustre/lustre/llite/llite_internal.h @@ -894,6 +894,10 @@ struct vvp_io { * fault API used bitflags for return code. */ unsigned int ft_flags; + /** + * check that flags are from filemap_fault + */ + bool ft_flags_valid; } fault; } fault; } u; diff --git a/drivers/staging/lustre/lustre/llite/llite_mmap.c b/drivers/staging/lustre/lustre/llite/llite_mmap.c index 7dae610..5916648 100644 --- a/drivers/staging/lustre/lustre/llite/llite_mmap.c +++ b/drivers/staging/lustre/lustre/llite/llite_mmap.c @@ -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_vmpage = NULL; 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); - fault_ret = vio->u.fault.fault.ft_flags; + /* 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; + vmpage = vio->u.fault.ft_vmpage; if (result != 0 && vmpage != NULL) { page_cache_release(vmpage); diff --git a/drivers/staging/lustre/lustre/llite/vvp_io.c b/drivers/staging/lustre/lustre/llite/vvp_io.c index a4117d6..fd24874 100644 --- a/drivers/staging/lustre/lustre/llite/vvp_io.c +++ b/drivers/staging/lustre/lustre/llite/vvp_io.c @@ -615,6 +615,7 @@ static int vvp_io_kernel_fault(struct vvp_fault_io *cfio) struct vm_fault *vmf = cfio->fault.ft_vmf; cfio->fault.ft_flags = filemap_fault(cfio->ft_vma, vmf); + cfio->fault.ft_flags_valid = 1; if (vmf->page) { CDEBUG(D_PAGE, -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
