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Tue, 17 Mar 2020 12:48:38 -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 72D92AD11; Tue, 17 Mar 2020 16:48:37 +0000 (UTC) Subject: Re: [PATCH 12/15] btrfs: get rid of one layer of bios in direct I/O To: Omar Sandoval , linux-btrfs@vger.kernel.org Cc: kernel-team@fb.com, Christoph Hellwig References: 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: Date: Tue, 17 Mar 2020 18:48:36 +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: 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 > > In the worst case, there are _4_ layers of bios in the Btrfs direct I/O > path: > > 1. The bio created by the generic direct I/O code (dio_bio). > 2. A clone of dio_bio we create in btrfs_submit_direct() to represent > the entire direct I/O range (orig_bio). > 3. A partial clone of orig_bio limited to the size of a RAID stripe that > we create in btrfs_submit_direct_hook(). > 4. Clones of each of those split bios for each RAID stripe that we > create in btrfs_map_bio(). > > As of the previous commit, the second layer (orig_bio) is no longer > needed for anything: we can split dio_bio instead, and complete dio_bio > directly when all of the cloned bios complete. This lets us clean up a > bunch of cruft, including dip->subio_endio and dip->errors (we can use > dio_bio->bi_status instead). It also enables the next big cleanup of > direct I/O read repair. > > Signed-off-by: Omar Sandoval > --- > fs/btrfs/inode.c | 213 +++++++++++++++-------------------------------- > 1 file changed, 66 insertions(+), 147 deletions(-) > > diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c > index 4a2e44f3e66e..40c1562704e9 100644 > --- a/fs/btrfs/inode.c > +++ b/fs/btrfs/inode.c > @@ -54,11 +54,8 @@ struct btrfs_iget_args { > struct btrfs_root *root; > }; > > @@ -7400,6 +7384,29 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock, > return ret; > } > > +static void btrfs_dio_private_put(struct btrfs_dio_private *dip) > +{ > + /* > + * This implies a barrier so that stores to dio_bio->bi_status before > + * this and the following load are fully ordered. > + */ It's not obvious which load this refers to. It's not obvious where this ordering matters i.e what are the threads that care? > + if (!refcount_dec_and_test(&dip->refs)) > + return; > + > + if (bio_op(dip->dio_bio) == REQ_OP_WRITE) { > + __endio_write_update_ordered(dip->inode, dip->logical_offset, > + dip->bytes, > + !dip->dio_bio->bi_status); > + } else { > + unlock_extent(&BTRFS_I(dip->inode)->io_tree, > + dip->logical_offset, > + dip->logical_offset + dip->bytes - 1); > + } > + > + dio_end_io(dip->dio_bio); > + kfree(dip); > +} > + > static inline blk_status_t submit_dio_repair_bio(struct inode *inode, > struct bio *bio, > int mirror_num) > @@ -7920,98 +7876,77 @@ static void btrfs_submit_direct_hook(struct btrfs_dio_private *dip) > struct inode *inode = dip->inode; > struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); > struct bio *bio; > - struct bio *orig_bio = dip->orig_bio; > - u64 start_sector = orig_bio->bi_iter.bi_sector; > + struct bio *dio_bio = dip->dio_bio; > + u64 start_sector = dio_bio->bi_iter.bi_sector; > u64 file_offset = dip->logical_offset; > int async_submit = 0; > - u64 submit_len; > + u64 submit_len = dio_bio->bi_iter.bi_size; > int clone_offset = 0; > int clone_len; > int ret; > blk_status_t status; > struct btrfs_io_geometry geom; > > - submit_len = orig_bio->bi_iter.bi_size; > - ret = btrfs_get_io_geometry(fs_info, btrfs_op(orig_bio), > - start_sector << 9, submit_len, &geom); > - if (ret) > - goto out_err; > - > - if (geom.len >= submit_len) { > - bio = orig_bio; > - dip->flags |= BTRFS_DIO_ORIG_BIO_SUBMITTED; > - goto submit; > - } > - > /* async crcs make it difficult to collect full stripe writes. */ > if (btrfs_data_alloc_profile(fs_info) & BTRFS_BLOCK_GROUP_RAID56_MASK) > async_submit = 0; > else > async_submit = 1; > > - /* bio split */ > ASSERT(geom.len <= INT_MAX); geom.len now contains some random data since it's no longer initialised, meaning this ASSERT hasn't triggered by pure luck. It should be (re)moved inside the do {} while loop. > do { > + ret = btrfs_get_io_geometry(fs_info, btrfs_op(dio_bio), > + start_sector << 9, submit_len, > + &geom); > + if (ret) { > + status = errno_to_blk_status(ret); > + goto out_err; > + } > + > clone_len = min_t(int, submit_len, geom.len); > > /* > * This will never fail as it's passing GPF_NOFS and > * the allocation is backed by btrfs_bioset. > */ > - bio = btrfs_bio_clone_partial(orig_bio, clone_offset, > - clone_len); > + bio = btrfs_bio_clone_partial(dio_bio, clone_offset, clone_len); > bio->bi_private = dip; > bio->bi_end_io = btrfs_end_dio_bio; > btrfs_io_bio(bio)->logical = file_offset; > > ASSERT(submit_len >= clone_len); > submit_len -= clone_len; > - if (submit_len == 0) > - break; > > /* > * Increase the count before we submit the bio so we know > * the end IO handler won't happen before we increase the > * count. Otherwise, the dip might get freed before we're > * done setting it up. > + * > + * We transfer the initial reference to the last bio, so we > + * don't need to increment the reference count for the last one. > */ > - refcount_inc(&dip->refs); > + if (submit_len > 0) > + refcount_inc(&dip->refs); > > status = btrfs_submit_dio_bio(bio, inode, file_offset, > async_submit); > if (status) { > bio_put(bio); > - refcount_dec(&dip->refs); > + if (submit_len > 0) > + refcount_dec(&dip->refs); > goto out_err; > } > > clone_offset += clone_len; > start_sector += clone_len >> 9; > file_offset += clone_len; > - > - ret = btrfs_get_io_geometry(fs_info, btrfs_op(orig_bio), > - start_sector << 9, submit_len, &geom); > - if (ret) > - goto out_err; > } while (submit_len > 0);> + return;