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Tue, 17 Mar 2020 10:38:48 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id BEA6DAE34; Tue, 17 Mar 2020 14:38:44 +0000 (UTC) Subject: Re: [PATCH 05/15] btrfs: clarify btrfs_lookup_bio_sums documentation To: Omar Sandoval , linux-btrfs@vger.kernel.org Cc: kernel-team@fb.com, Christoph Hellwig References: <2ee5f090b52dc23569bf94a5a2609dfc49ac4a4b.1583789410.git.osandov@fb.com> From: Nikolay Borisov Autocrypt: addr=nborisov@suse.com; prefer-encrypt=mutual; keydata= xsFNBFiKBz4BEADNHZmqwhuN6EAzXj9SpPpH/nSSP8YgfwoOqwrP+JR4pIqRK0AWWeWCSwmZ T7g+RbfPFlmQp+EwFWOtABXlKC54zgSf+uulGwx5JAUFVUIRBmnHOYi/lUiE0yhpnb1KCA7f u/W+DkwGerXqhhe9TvQoGwgCKNfzFPZoM+gZrm+kWv03QLUCr210n4cwaCPJ0Nr9Z3c582xc bCUVbsjt7BN0CFa2BByulrx5xD9sDAYIqfLCcZetAqsTRGxM7LD0kh5WlKzOeAXj5r8DOrU2 GdZS33uKZI/kZJZVytSmZpswDsKhnGzRN1BANGP8sC+WD4eRXajOmNh2HL4P+meO1TlM3GLl EQd2shHFY0qjEo7wxKZI1RyZZ5AgJnSmehrPCyuIyVY210CbMaIKHUIsTqRgY5GaNME24w7h TyyVCy2qAM8fLJ4Vw5bycM/u5xfWm7gyTb9V1TkZ3o1MTrEsrcqFiRrBY94Rs0oQkZvunqia c+NprYSaOG1Cta14o94eMH271Kka/reEwSZkC7T+o9hZ4zi2CcLcY0DXj0qdId7vUKSJjEep c++s8ncFekh1MPhkOgNj8pk17OAESanmDwksmzh1j12lgA5lTFPrJeRNu6/isC2zyZhTwMWs k3LkcTa8ZXxh0RfWAqgx/ogKPk4ZxOXQEZetkEyTFghbRH2BIwARAQABzSJOaWtvbGF5IEJv cmlzb3YgPG5ib3Jpc292QHN1c2UuZGU+wsF4BBMBAgAiBQJYijkSAhsDBgsJCAcDAgYVCAIJ CgsEFgIDAQIeAQIXgAAKCRBxvoJG5T8oV/B6D/9a8EcRPdHg8uLEPywuJR8URwXzkofT5bZE IfGF0Z+Lt2ADe+nLOXrwKsamhweUFAvwEUxxnndovRLPOpWerTOAl47lxad08080jXnGfYFS Dc+ew7C3SFI4tFFHln8Y22Q9075saZ2yQS1ywJy+TFPADIprAZXnPbbbNbGtJLoq0LTiESnD w/SUC6sfikYwGRS94Dc9qO4nWyEvBK3Ql8NkoY0Sjky3B0vL572Gq0ytILDDGYuZVo4alUs8 LeXS5ukoZIw1QYXVstDJQnYjFxYgoQ5uGVi4t7FsFM/6ykYDzbIPNOx49Rbh9W4uKsLVhTzG BDTzdvX4ARl9La2kCQIjjWRg+XGuBM5rxT/NaTS78PXjhqWNYlGc5OhO0l8e5DIS2tXwYMDY LuHYNkkpMFksBslldvNttSNei7xr5VwjVqW4vASk2Aak5AleXZS+xIq2FADPS/XSgIaepyTV tkfnyreep1pk09cjfXY4A7qpEFwazCRZg9LLvYVc2M2eFQHDMtXsH59nOMstXx2OtNMcx5p8 0a5FHXE/HoXz3p9bD0uIUq6p04VYOHsMasHqHPbsMAq9V2OCytJQPWwe46bBjYZCOwG0+x58 fBFreP/NiJNeTQPOa6FoxLOLXMuVtpbcXIqKQDoEte9aMpoj9L24f60G4q+pL/54ql2VRscK d87BTQRYigc+ARAAyJSq9EFk28++SLfg791xOh28tLI6Yr8wwEOvM3wKeTfTZd+caVb9gBBy wxYhIopKlK1zq2YP7ZjTP1aPJGoWvcQZ8fVFdK/1nW+Z8/NTjaOx1mfrrtTGtFxVBdSCgqBB jHTnlDYV1R5plJqK+ggEP1a0mr/rpQ9dFGvgf/5jkVpRnH6BY0aYFPprRL8ZCcdv2DeeicOO YMobD5g7g/poQzHLLeT0+y1qiLIFefNABLN06Lf0GBZC5l8hCM3Rpb4ObyQ4B9PmL/KTn2FV Xq/c0scGMdXD2QeWLePC+yLMhf1fZby1vVJ59pXGq+o7XXfYA7xX0JsTUNxVPx/MgK8aLjYW hX+TRA4bCr4uYt/S3ThDRywSX6Hr1lyp4FJBwgyb8iv42it8KvoeOsHqVbuCIGRCXqGGiaeX Wa0M/oxN1vJjMSIEVzBAPi16tztL/wQtFHJtZAdCnuzFAz8ue6GzvsyBj97pzkBVacwp3/Mw qbiu7sDz7yB0d7J2tFBJYNpVt/Lce6nQhrvon0VqiWeMHxgtQ4k92Eja9u80JDaKnHDdjdwq FUikZirB28UiLPQV6PvCckgIiukmz/5ctAfKpyYRGfez+JbAGl6iCvHYt/wAZ7Oqe/3Cirs5 KhaXBcMmJR1qo8QH8eYZ+qhFE3bSPH446+5oEw8A9v5oonKV7zMAEQEAAcLBXwQYAQIACQUC WIoHPgIbDAAKCRBxvoJG5T8oV1pyD/4zdXdOL0lhkSIjJWGqz7Idvo0wjVHSSQCbOwZDWNTN JBTP0BUxHpPu/Z8gRNNP9/k6i63T4eL1xjy4umTwJaej1X15H8Hsh+zakADyWHadbjcUXCkg OJK4NsfqhMuaIYIHbToi9K5pAKnV953xTrK6oYVyd/Rmkmb+wgsbYQJ0Ur1Ficwhp6qU1CaJ mJwFjaWaVgUERoxcejL4ruds66LM9Z1Qqgoer62ZneID6ovmzpCWbi2sfbz98+kW46aA/w8r 7sulgs1KXWhBSv5aWqKU8C4twKjlV2XsztUUsyrjHFj91j31pnHRklBgXHTD/pSRsN0UvM26 lPs0g3ryVlG5wiZ9+JbI3sKMfbdfdOeLxtL25ujs443rw1s/PVghphoeadVAKMPINeRCgoJH zZV/2Z/myWPRWWl/79amy/9MfxffZqO9rfugRBORY0ywPHLDdo9Kmzoxoxp9w3uTrTLZaT9M KIuxEcV8wcVjr+Wr9zRl06waOCkgrQbTPp631hToxo+4rA1jiQF2M80HAet65ytBVR2pFGZF zGYYLqiG+mpUZ+FPjxk9kpkRYz61mTLSY7tuFljExfJWMGfgSg1OxfLV631jV1TcdUnx+h3l Sqs2vMhAVt14zT8mpIuu2VNxcontxgVr1kzYA/tQg32fVRbGr449j1gw57BV9i0vww== Message-ID: <5b07260c-5fd6-f01c-0dde-fcc224a11f79@suse.com> Date: Tue, 17 Mar 2020 16:38:44 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <2ee5f090b52dc23569bf94a5a2609dfc49ac4a4b.1583789410.git.osandov@fb.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 9.03.20 г. 23:32 ч., Omar Sandoval wrote: > From: Omar Sandoval > > Fix a couple of issues in the btrfs_lookup_bio_sums documentation: > > * The bio doesn't need to be a btrfs_io_bio if dst was provided. Move > the declaration in the code to make that clear, too. > * dst must be large enough to hold nblocks * csum_size, not just > csum_size. > > Signed-off-by: Omar Sandoval > --- > fs/btrfs/file-item.c | 11 +++++++---- > 1 file changed, 7 insertions(+), 4 deletions(-) > > diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c > index 6c849e8fd5a1..fa9f4a92f74d 100644 > --- a/fs/btrfs/file-item.c > +++ b/fs/btrfs/file-item.c > @@ -242,11 +242,13 @@ int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans, > /** > * btrfs_lookup_bio_sums - Look up checksums for a bio. > * @inode: inode that the bio is for. > - * @bio: bio embedded in btrfs_io_bio. > + * @bio: bio to look up. > * @offset: Unless (u64)-1, look up checksums for this offset in the file. > * If (u64)-1, use the page offsets from the bio instead. > - * @dst: Buffer of size btrfs_super_csum_size() used to return checksum. If > - * NULL, the checksum is returned in btrfs_io_bio(bio)->csum instead. > + * @dst: Buffer of size nblocks * btrfs_super_csum_size() used to return > + * checksum (nblocks = bio->bi_iter.bi_size / sectorsize). If NULL, the nit: sector here refers to btrfs' notion of a sector which is 4k and not the default understanding of 512 bytes. Dunno if it makes sense to make that a bit more emphatic. Also nblocks is really number of checksums. Looking at file-item.c I see there is only 1 menition of ncsums or csums_in_item. I guess if we can make that nblocks a bit more explicit? > + * checksum buffer is allocated and returned in btrfs_io_bio(bio)->csum > + * instead. > * > * Return: BLK_STS_RESOURCE if allocating memory fails, BLK_STS_OK otherwise. > */ > @@ -256,7 +258,6 @@ blk_status_t btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio, > struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); > struct bio_vec bvec; > struct bvec_iter iter; > - struct btrfs_io_bio *btrfs_bio = btrfs_io_bio(bio); > struct btrfs_csum_item *item = NULL; > struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree; > struct btrfs_path *path; > @@ -277,6 +278,8 @@ blk_status_t btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio, > > nblocks = bio->bi_iter.bi_size >> inode->i_sb->s_blocksize_bits; > if (!dst) { > + struct btrfs_io_bio *btrfs_bio = btrfs_io_bio(bio); > + > if (nblocks * csum_size > BTRFS_BIO_INLINE_CSUM_SIZE) { > btrfs_bio->csum = kmalloc_array(nblocks, csum_size, > GFP_NOFS); >