From patchwork Wed Nov 22 23:28:15 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kent Overstreet X-Patchwork-Id: 13465569 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="q8FMhX4D" Received: from out-187.mta0.migadu.com (out-187.mta0.migadu.com [91.218.175.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5F854110 for ; Wed, 22 Nov 2023 15:28:28 -0800 (PST) X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1700695706; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=wdxKnJ2FmIDaRAshfSUcmrGs+dMUGZeUTYVCPDJSnpk=; b=q8FMhX4D68JVMtBwOlZC8K7WTFcuV7dFt6Tdp+yJPOCFEpENVPE1X/9EsC7aj4rSAKviNs YXezFsQOaw4edYpaUeU3NRGO/ewnZZTbyesH4EgJzwvsM/xIaMGMlYZkbPYW7OSL+/FYyJ ghl5q/SL7SVDzkrhNFrysTuy3zB75cs= From: Kent Overstreet To: axboe@kernel.dk, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org Cc: Kent Overstreet , Ming Lei Subject: [PATCH 3/3] block: Add documentation for bio iterator macros Date: Wed, 22 Nov 2023 18:28:15 -0500 Message-ID: <20231122232818.178256-3-kent.overstreet@linux.dev> In-Reply-To: <20231122232818.178256-1-kent.overstreet@linux.dev> References: <20231122232818.178256-1-kent.overstreet@linux.dev> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Migadu-Flow: FLOW_OUT We've now got 3x2 interfaces for iterating over bios: by page, by bvec, or by folio, and variants that iterate over what bi_iter points to, or the entire bio as created by the filesystem/originator. This adds more detailed kerneldoc comments for each variant. Signed-off-by: Kent Overstreet Cc: Jens Axboe Cc: Ming Lei Cc: linux-block@vger.kernel.org Reviewed-by: Ming Lei --- include/linux/bio.h | 54 ++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 48 insertions(+), 6 deletions(-) diff --git a/include/linux/bio.h b/include/linux/bio.h index eaaf7e5f0d54..21524a953f6e 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -103,9 +103,14 @@ static inline void bio_iter_all_advance(const struct bio *bio, ((bvl = bio_iter_all_peek(bio, &iter)), true); \ bio_iter_all_advance((bio), &iter, bvl.bv_len)) -/* - * drivers should _never_ use the all version - the bio may have been split - * before it got to the driver and the driver won't own all of it +/** + * bio_for_each_segment_all - iterate over single pages in a bio + * + * Like other _all versions, this is for the filesystem, or the owner/creator of + * a bio; it iterates over the original contents of a bio. + * + * Drivers that are working with bios that were submitted to them should not use + * the _all version. */ #define bio_for_each_segment_all(bvl, bio, iter) \ for (bvec_iter_all_init(&iter); \ @@ -166,6 +171,13 @@ static inline void bio_advance(struct bio *bio, unsigned int nbytes) ((bvl = bio_iter_iovec((bio), (iter))), 1); \ bio_advance_iter_single((bio), &(iter), (bvl).bv_len)) +/** + * bio_for_each_segment - iterate over single pages in a bio + * + * Like other non-_all versions, this iterates over what bio->bi_iter currently + * points to. This version is for drivers, where the bio may have previously + * been split or cloned. + */ #define bio_for_each_segment(bvl, bio, iter) \ __bio_for_each_segment(bvl, bio, iter, (bio)->bi_iter) @@ -202,6 +214,13 @@ static inline struct folio_vec bio_iter_iovec_folio(struct bio *bio, ((bvl = bio_iter_iovec_folio((bio), (iter))), 1); \ bio_advance_iter_single((bio), &(iter), (bvl).fv_len)) +/** + * bio_for_each_folio - iterate over folios within a bio + * + * Like other non-_all versions, this iterates over what bio->bi_iter currently + * points to. This version is for drivers, where the bio may have previously + * been split or cloned. + */ #define bio_for_each_folio(bvl, bio, iter) \ __bio_for_each_folio(bvl, bio, iter, (bio)->bi_iter) @@ -211,13 +230,30 @@ static inline struct folio_vec bio_iter_iovec_folio(struct bio *bio, ((bvl = mp_bvec_iter_bvec((bio)->bi_io_vec, (iter))), 1); \ bio_advance_iter_single((bio), &(iter), (bvl).bv_len)) -/* iterate over multi-page bvec */ +/** + * bio_for_each_bvec - iterate over bvecs within a bio + * + * This version iterates over entire bio_vecs, which will be a range of + * contiguous pages. + * + * Like other non-_all versions, this iterates over what bio->bi_iter currently + * points to. This version is for drivers, where the bio may have previously + * been split or cloned. + */ #define bio_for_each_bvec(bvl, bio, iter) \ __bio_for_each_bvec(bvl, bio, iter, (bio)->bi_iter) /* - * Iterate over all multi-page bvecs. Drivers shouldn't use this version for the - * same reasons as bio_for_each_segment_all(). + * bio_for_each_bvec_all - iterate over bvecs within a bio + * + * This version iterates over entire bio_vecs, which will be a range of + * contiguous pages. + * + * Like other _all versions, this is for the filesystem, or the owner/creator of + * a bio; it iterates over the original contents of a bio. + * + * Drivers that are working with bios that were submitted to them should not use + * the _all version. */ #define bio_for_each_bvec_all(bvl, bio, i) \ for (i = 0, bvl = bio_first_bvec_all(bio); \ @@ -328,6 +364,12 @@ static inline struct folio_vec bio_folio_iter_all_peek(const struct bio *bio, * bio_for_each_folio_all - Iterate over each folio in a bio. * @fi: struct bio_folio_iter_all which is updated for each folio. * @bio: struct bio to iterate over. + * + * Like other _all versions, this is for the filesystem, or the owner/creator of + * a bio; it iterates over the original contents of a bio. + * + * Drivers that are working with bios that were submitted to them should not use + * the _all version. */ #define bio_for_each_folio_all(fv, bio, iter) \ for (bvec_iter_all_init(&iter); \