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Date:   Fri, 15 Sep 2023 14:44:58 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Daniel Gomez <da.gomez@samsung.com>
Cc:     "minchan@kernel.org" <minchan@kernel.org>,
        "senozhatsky@chromium.org" <senozhatsky@chromium.org>,
        "axboe@kernel.dk" <axboe@kernel.dk>,
        "djwong@kernel.org" <djwong@kernel.org>,
        "hughd@google.com" <hughd@google.com>,
        "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
        "mcgrof@kernel.org" <mcgrof@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
        "linux-xfs@vger.kernel.org" <linux-xfs@vger.kernel.org>,
        "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "gost.dev@samsung.com" <gost.dev@samsung.com>,
        Pankaj Raghav <p.raghav@samsung.com>
Subject: Re: [PATCH 3/6] shmem: account for large order folios
Message-ID: <ZQRf2pGWurrE0uO+@casper.infradead.org>
References: <20230915095042.1320180-1-da.gomez@samsung.com>
 <CGME20230915095128eucas1p2885c3add58d82413d9c1d17832d3d281@eucas1p2.samsung.com>
 <20230915095042.1320180-4-da.gomez@samsung.com>
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In-Reply-To: <20230915095042.1320180-4-da.gomez@samsung.com>
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On Fri, Sep 15, 2023 at 09:51:26AM +0000, Daniel Gomez wrote:
> +	xas_for_each(&xas, folio, max) {
> +		if (xas_retry(&xas, folio))
>  			continue;
> -		if (xa_is_value(page))
> -			swapped++;
> +		if (xa_is_value(folio))
> +			swapped += (folio_nr_pages(folio));

Unnecessary parens.

> @@ -1006,10 +1006,12 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
>  			folio = fbatch.folios[i];
>  
>  			if (xa_is_value(folio)) {
> +				long swaps_freed;
>  				if (unfalloc)
>  					continue;
> -				nr_swaps_freed += !shmem_free_swap(mapping,
> -							indices[i], folio);
> +				swaps_freed = folio_nr_pages(folio);
> +				if (!shmem_free_swap(mapping, indices[i], folio))
> +					nr_swaps_freed += swaps_freed;

Broader change (indeed, in a separate patch), why not make
shmem_free_swap() return the number of pages freed, rather than
returning an errno?

> @@ -1075,14 +1077,16 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
>  			folio = fbatch.folios[i];
>  
>  			if (xa_is_value(folio)) {
> +				long swaps_freed;
>  				if (unfalloc)
>  					continue;
> +				swaps_freed = folio_nr_pages(folio);
>  				if (shmem_free_swap(mapping, indices[i], folio)) {
>  					/* Swap was replaced by page: retry */
>  					index = indices[i];
>  					break;
>  				}
> -				nr_swaps_freed++;
> +				nr_swaps_freed += swaps_freed;
>  				continue;

... seems like both callers would prefer that.