From mboxrd@z Thu Jan 1 00:00:00 1970 From: Goldwyn Rodrigues Subject: [PATCH 02/10] fs: Introduce filemap_range_has_page() Date: Thu, 11 May 2017 14:17:02 -0500 Message-ID: <20170511191710.31959-3-rgoldwyn@suse.de> References: <20170511191710.31959-1-rgoldwyn@suse.de> Return-path: In-Reply-To: <20170511191710.31959-1-rgoldwyn@suse.de> Sender: linux-block-owner@vger.kernel.org To: linux-fsdevel@vger.kernel.org Cc: jack@suse.com, hch@infradead.org, linux-block@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, sagi@grimberg.me, avi@scylladb.com, axboe@kernel.dk, linux-api@vger.kernel.org, Goldwyn Rodrigues List-Id: linux-api@vger.kernel.org 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. Signed-off-by: Goldwyn Rodrigues Reviewed-by: Christoph Hellwig --- include/linux/fs.h | 2 ++ mm/filemap.c | 33 +++++++++++++++++++++++++++++++++ 2 files changed, 35 insertions(+) diff --git a/include/linux/fs.h b/include/linux/fs.h index 869c9a6fe58d..2e6fc6a23f91 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2513,6 +2513,8 @@ 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 1694623a6289..fae5a361befb 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 + * @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) +{ + 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); + static int __filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte, loff_t end_byte) { -- 2.12.0