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Date: Thu, 9 Nov 2023 17:37:28 +0000 From: Matthew Wilcox <willy@...radead.org> To: Andrew Morton <akpm@...ux-foundation.org> Cc: linux-ext4@...r.kernel.org, gfs2@...ts.linux.dev, linux-fsdevel@...r.kernel.org, linux-xfs@...r.kernel.org, "Darrick J . Wong" <djwong@...nel.org>, linux-erofs@...ts.ozlabs.org, Theodore Ts'o <tytso@....edu>, Andreas Dilger <adilger.kernel@...ger.ca>, Andreas Gruenbacher <agruenba@...hat.com> Subject: Re: [PATCH 1/3] mm: Add folio_zero_tail() and use it in ext4 On Wed, Nov 08, 2023 at 03:06:06PM -0800, Andrew Morton wrote: > > > > +/** > > + * folio_zero_tail - Zero the tail of a folio. > > + * @folio: The folio to zero. > > + * @kaddr: The address the folio is currently mapped to. > > + * @offset: The byte offset in the folio to start zeroing at. > > That's the argument ordering I would expect. > > > + * If you have already used kmap_local_folio() to map a folio, written > > + * some data to it and now need to zero the end of the folio (and flush > > + * the dcache), you can use this function. If you do not have the > > + * folio kmapped (eg the folio has been partially populated by DMA), > > + * use folio_zero_range() or folio_zero_segment() instead. > > + * > > + * Return: An address which can be passed to kunmap_local(). > > + */ > > +static inline __must_check void *folio_zero_tail(struct folio *folio, > > + size_t offset, void *kaddr) > > While that is not. addr,len is far more common that len,addr? But that's not len! That's offset-in-the-folio. ie we're doing: memset(folio_address(folio) + offset, 0, folio_size(folio) - offset); If we were doing: memset(folio_address(folio), 0, len); then yes, your suggestion is the right order. Indeed, having the arguments in the current order would hopefully make filesystem authors realise that this _isn't_ "len".
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