linux-kernel - Re: [PATCH v4 34/66] cxl: Remove vma linked list walk

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Message-ID: <20220125163217.fhzjqkhr27tx2nbp@revolver>
Date:   Tue, 25 Jan 2022 16:32:24 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     Vlastimil Babka <vbabka@...e.cz>
CC:     "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Song Liu <songliubraving@...com>,
        Davidlohr Bueso <dave@...olabs.net>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Laurent Dufour <ldufour@...ux.ibm.com>,
        David Rientjes <rientjes@...gle.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Rik van Riel <riel@...riel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Michel Lespinasse <walken.cr@...il.com>,
        Jerome Glisse <jglisse@...hat.com>,
        Minchan Kim <minchan@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Rom Lemarchand <romlem@...gle.com>
Subject: Re: [PATCH v4 34/66] cxl: Remove vma linked list walk

* Vlastimil Babka <vbabka@...e.cz> [220118 07:37]:
> On 12/1/21 15:30, Liam Howlett wrote:
> > From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
> > 
> > Use the VMA iterator instead.  This requires a little restructuring
> > of the surrounding code to hoist the mm to the caller.  That turns
> > cxl_prefault_one() into a trivial function, so call cxl_fault_segment()
> > directly.
> > 
> > Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> > Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> > ---
> >  drivers/misc/cxl/fault.c | 43 +++++++++++++---------------------------
> >  1 file changed, 14 insertions(+), 29 deletions(-)
> > 
> > diff --git a/drivers/misc/cxl/fault.c b/drivers/misc/cxl/fault.c
> > index 60c829113299..504522a126b5 100644
> > --- a/drivers/misc/cxl/fault.c
> > +++ b/drivers/misc/cxl/fault.c
> > @@ -280,22 +280,6 @@ void cxl_handle_fault(struct work_struct *fault_work)
> >  		mmput(mm);
> >  }
> >  
> > -static void cxl_prefault_one(struct cxl_context *ctx, u64 ea)
> > -{
> > -	struct mm_struct *mm;
> > -
> > -	mm = get_mem_context(ctx);
> > -	if (mm == NULL) {
> > -		pr_devel("cxl_prefault_one unable to get mm %i\n",
> > -			 pid_nr(ctx->pid));
> > -		return;
> > -	}
> > -
> > -	cxl_fault_segment(ctx, mm, ea);
> > -
> > -	mmput(mm);
> > -}
> > -
> >  static u64 next_segment(u64 ea, u64 vsid)
> >  {
> >  	if (vsid & SLB_VSID_B_1T)
> > @@ -306,23 +290,16 @@ static u64 next_segment(u64 ea, u64 vsid)
> >  	return ea + 1;
> >  }
> >  
> > -static void cxl_prefault_vma(struct cxl_context *ctx)
> > +static void cxl_prefault_vma(struct cxl_context *ctx, struct mm_struct *mm)
> >  {
> >  	u64 ea, last_esid = 0;
> >  	struct copro_slb slb;
> > +	VMA_ITERATOR(vmi, mm, 0);
> >  	struct vm_area_struct *vma;
> >  	int rc;
> > -	struct mm_struct *mm;
> > -
> > -	mm = get_mem_context(ctx);
> > -	if (mm == NULL) {
> > -		pr_devel("cxl_prefault_vm unable to get mm %i\n",
> > -			 pid_nr(ctx->pid));
> > -		return;
> > -	}
> >  
> >  	mmap_read_lock(mm);
> > -	for (vma = mm->mmap; vma; vma = vma->vm_next) {
> > +	for_each_vma(vmi, vma) {
> >  		for (ea = vma->vm_start; ea < vma->vm_end;
> >  				ea = next_segment(ea, slb.vsid)) {
> >  			rc = copro_calculate_slb(mm, ea, &slb);
> > @@ -337,15 +314,21 @@ static void cxl_prefault_vma(struct cxl_context *ctx)
> >  		}
> >  	}
> >  	mmap_read_unlock(mm);
> > -
> > -	mmput(mm);
> >  }
> >  
> >  void cxl_prefault(struct cxl_context *ctx, u64 wed)
> >  {
> > +	struct mm_struct *mm = get_mem_context(ctx);
> > +
> > +	if (mm == NULL) {
> > +		pr_devel("cxl_prefault unable to get mm %i\n",
> > +			 pid_nr(ctx->pid));
> > +		return;
> > +	}
> > +
> >  	switch (ctx->afu->prefault_mode) {
> >  	case CXL_PREFAULT_WED:
> > -		cxl_prefault_one(ctx, wed);
> > +		cxl_fault_segment(ctx, mm, wed);
> >  		break;
> >  	case CXL_PREFAULT_ALL:
> >  		cxl_prefault_vma(ctx);
> 
> Need to pass mm here, compile tested much? :)

ack.

> 
> After fixup
> Acked-by: Vlastimil Babka <vbabka@...e.cz>
> 
> > @@ -353,4 +336,6 @@ void cxl_prefault(struct cxl_context *ctx, u64 wed)
> >  	default:
> >  		break;
> >  	}
> > +
> > +	mmput(mm);
> >  }
>