linux-kernel - Re: [PATCH v3 1/2] filemap: find_lock_entries() now updates start offset

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Message-ID: <Y02JTOtYEbAyo+zu@casper.infradead.org>
Date:   Mon, 17 Oct 2022 17:56:44 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     "Vishal Moola (Oracle)" <vishal.moola@...il.com>
Cc:     akpm@...ux-foundation.org, hughd@...gle.com,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/2] filemap: find_lock_entries() now updates start
 offset

On Mon, Oct 17, 2022 at 09:17:59AM -0700, Vishal Moola (Oracle) wrote:
> +++ b/mm/shmem.c
> @@ -932,21 +932,18 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
>  
>  	folio_batch_init(&fbatch);
>  	index = start;
> -	while (index < end && find_lock_entries(mapping, index, end - 1,
> +	while (index < end && find_lock_entries(mapping, &index, end - 1,

Sorry for not spotting this in earlier revisions, but this is wrong.
Before, find_lock_entries() would go up to (end - 1) and then the
index++ at the end of the loop would increment index to "end", causing
the loop to terminate.  Now we don't increment index any more, so the
condition is wrong.

I suggest just removing the 'index < end" half of the condition.

> @@ -361,9 +361,8 @@ void truncate_inode_pages_range(struct address_space *mapping,
>  
>  	folio_batch_init(&fbatch);
>  	index = start;
> -	while (index < end && find_lock_entries(mapping, index, end - 1,
> +	while (index < end && find_lock_entries(mapping, &index, end - 1,
>  			&fbatch, indices)) {

Similarly here.

> @@ -510,20 +509,17 @@ unsigned long invalidate_mapping_pagevec(struct address_space *mapping,
>  	int i;
>  
>  	folio_batch_init(&fbatch);
> -	while (find_lock_entries(mapping, index, end, &fbatch, indices)) {
> +	while (find_lock_entries(mapping, &index, end, &fbatch, indices)) {

While this one had the check removed already, so is fine ;-)