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

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Date:   Tue, 18 Jan 2022 13:37:07 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Liam Howlett <liam.howlett@...cle.com>,
        "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>
Cc:     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

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? :)

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);
>  }