From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Thu, 15 Jun 2017 11:25:33 -0700 From: Andrew Morton To: Goldwyn Rodrigues Cc: linux-fsdevel@vger.kernel.org, jack@suse.com, hch@infradead.org, linux-block@vger.kernel.org, axboe@kernel.dk, linux-api@vger.kernel.org, viro@zeniv.linux.org.uk, Goldwyn Rodrigues Subject: Re: [PATCH 02/10] fs: Introduce filemap_range_has_page() Message-Id: <20170615112533.36d21ee582c968f6d5dec42f@linux-foundation.org> In-Reply-To: <20170615160002.17233-3-rgoldwyn@suse.de> References: <20170615160002.17233-1-rgoldwyn@suse.de> <20170615160002.17233-3-rgoldwyn@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII List-ID: On Thu, 15 Jun 2017 10:59:54 -0500 Goldwyn Rodrigues wrote: > From: Goldwyn Rodrigues > > filemap_range_has_page() return true if the file's mapping has > a page within the range mentioned. This function will be used > to check if a write() call will cause a writeback of previous > writes. > > ... > > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -2517,6 +2517,8 @@ extern int filemap_fdatawait(struct address_space *); > extern void filemap_fdatawait_keep_errors(struct address_space *); > extern int filemap_fdatawait_range(struct address_space *, loff_t lstart, > loff_t lend); > +extern int filemap_range_has_page(struct address_space *, loff_t lstart, > + loff_t lend); > extern int filemap_write_and_wait(struct address_space *mapping); > extern int filemap_write_and_wait_range(struct address_space *mapping, > loff_t lstart, loff_t lend); > diff --git a/mm/filemap.c b/mm/filemap.c > index 6f1be573a5e6..87aba7698584 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -376,6 +376,39 @@ int filemap_flush(struct address_space *mapping) > } > EXPORT_SYMBOL(filemap_flush); > > +/** > + * filemap_range_has_page - check if a page exists in range. > + * @mapping: address space structure to wait for "to wait for" seems wrong. > + * @start_byte: offset in bytes where the range starts > + * @end_byte: offset in bytes where the range ends (inclusive) > + * > + * Find at least one page in the range supplied, usually used to check if > + * direct writing in this range will trigger a writeback. > + */ > +int filemap_range_has_page(struct address_space *mapping, > + loff_t start_byte, loff_t end_byte) Would a bool return type be better? > +{ > + pgoff_t index = start_byte >> PAGE_SHIFT; > + pgoff_t end = end_byte >> PAGE_SHIFT; > + struct pagevec pvec; > + int ret; > + > + if (end_byte < start_byte) > + return 0; > + > + if (mapping->nrpages == 0) > + return 0; > + > + pagevec_init(&pvec, 0); > + ret = pagevec_lookup(&pvec, mapping, index, 1); > + if (!ret) > + return 0; > + ret = (pvec.pages[0]->index <= end); > + pagevec_release(&pvec); > + return ret; > +} > +EXPORT_SYMBOL(filemap_range_has_page); > +