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Thu, 4 Jan 2024 12:22:14 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id aIvDJ/ailmWuFQAAD6G6ig (envelope-from ); Thu, 04 Jan 2024 12:22:14 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id 12451A07EF; Thu, 4 Jan 2024 13:22:14 +0100 (CET) Date: Thu, 4 Jan 2024 13:22:14 +0100 From: Jan Kara To: Yu Kuai Cc: axboe@kernel.dk, roger.pau@citrix.com, colyli@suse.de, kent.overstreet@gmail.com, joern@lazybastard.org, miquel.raynal@bootlin.com, richard@nod.at, vigneshr@ti.com, sth@linux.ibm.com, hoeppner@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, jejb@linux.ibm.com, martin.petersen@oracle.com, clm@fb.com, josef@toxicpanda.com, dsterba@suse.com, viro@zeniv.linux.org.uk, brauner@kernel.org, nico@fluxnic.net, xiang@kernel.org, chao@kernel.org, tytso@mit.edu, adilger.kernel@dilger.ca, jack@suse.com, konishi.ryusuke@gmail.com, willy@infradead.org, akpm@linux-foundation.org, hare@suse.de, p.raghav@samsung.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org, linux-bcache@vger.kernel.org, linux-mtd@lists.infradead.org, linux-s390@vger.kernel.org, linux-scsi@vger.kernel.org, linux-bcachefs@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-ext4@vger.kernel.org, linux-nilfs@vger.kernel.org, yukuai3@huawei.com, yi.zhang@huawei.com, yangerkun@huawei.com Subject: Re: [PATCH RFC v3 for-6.8/block 14/17] buffer: add a new helper to read sb block Message-ID: <20240104122214.jndsqygnmljxmj5d@quack3> References: <20231221085712.1766333-1-yukuai1@huaweicloud.com> <20231221085853.1770062-1-yukuai1@huaweicloud.com> Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; 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MID_RHS_NOT_FQDN(0.50)[]; FREEMAIL_CC(0.00)[kernel.dk,citrix.com,suse.de,gmail.com,lazybastard.org,bootlin.com,nod.at,ti.com,linux.ibm.com,oracle.com,fb.com,toxicpanda.com,suse.com,zeniv.linux.org.uk,kernel.org,fluxnic.net,mit.edu,dilger.ca,infradead.org,linux-foundation.org,samsung.com,vger.kernel.org,lists.xenproject.org,lists.infradead.org,lists.ozlabs.org,huawei.com]; RCVD_TLS_ALL(0.00)[]; SUSPICIOUS_RECIPS(1.50)[]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from] Authentication-Results: smtp-out1.suse.de; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=dWaipx2c; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=VFhD00b5 X-Spam-Score: -1.31 X-Rspamd-Queue-Id: C3FE921D3A On Thu 21-12-23 16:58:53, Yu Kuai wrote: > From: Yu Kuai > > Unlike __bread_gfp(), ext4 has special handing while reading sb block: > > 1) __GFP_NOFAIL is not set, and memory allocation can fail; > 2) If buffer write failed before, set buffer uptodate and don't read > block from disk; > 3) REQ_META is set for all IO, and REQ_PRIO is set for reading xattr; > 4) If failed, return error ptr instead of NULL; > > This patch add a new helper __bread_gfp2() that will match above 2 and 3( > 1 will be used, and 4 will still be encapsulated by ext4), and prepare to > prevent calling mapping_gfp_constraint() directly on bd_inode->i_mapping > in ext4. > > Signed-off-by: Yu Kuai I'm not enthusiastic about this but I guess it is as good as it gets without larger cleanups in this area. So feel free to add: Reviewed-by: Jan Kara Honza > --- > fs/buffer.c | 68 ++++++++++++++++++++++++++----------- > include/linux/buffer_head.h | 18 +++++++++- > 2 files changed, 65 insertions(+), 21 deletions(-) > > diff --git a/fs/buffer.c b/fs/buffer.c > index 967f34b70aa8..188bd36c9fea 100644 > --- a/fs/buffer.c > +++ b/fs/buffer.c > @@ -1255,16 +1255,19 @@ void __bforget(struct buffer_head *bh) > } > EXPORT_SYMBOL(__bforget); > > -static struct buffer_head *__bread_slow(struct buffer_head *bh) > +static struct buffer_head *__bread_slow(struct buffer_head *bh, > + blk_opf_t op_flags, > + bool check_write_error) > { > lock_buffer(bh); > - if (buffer_uptodate(bh)) { > + if (buffer_uptodate(bh) || > + (check_write_error && buffer_uptodate_or_error(bh))) { > unlock_buffer(bh); > return bh; > } else { > get_bh(bh); > bh->b_end_io = end_buffer_read_sync; > - submit_bh(REQ_OP_READ, bh); > + submit_bh(REQ_OP_READ | op_flags, bh); > wait_on_buffer(bh); > if (buffer_uptodate(bh)) > return bh; > @@ -1445,6 +1448,31 @@ void __breadahead(struct block_device *bdev, sector_t block, unsigned size) > } > EXPORT_SYMBOL(__breadahead); > > +static struct buffer_head * > +bread_gfp(struct block_device *bdev, sector_t block, unsigned int size, > + blk_opf_t op_flags, gfp_t gfp, bool check_write_error) > +{ > + struct buffer_head *bh; > + > + gfp |= mapping_gfp_constraint(bdev->bd_inode->i_mapping, ~__GFP_FS); > + > + /* > + * Prefer looping in the allocator rather than here, at least that > + * code knows what it's doing. > + */ > + gfp |= __GFP_NOFAIL; > + > + bh = bdev_getblk(bdev, block, size, gfp); > + if (unlikely(!bh)) > + return NULL; > + > + if (buffer_uptodate(bh) || > + (check_write_error && buffer_uptodate_or_error(bh))) > + return bh; > + > + return __bread_slow(bh, op_flags, check_write_error); > +} > + > /** > * __bread_gfp() - reads a specified block and returns the bh > * @bdev: the block_device to read from > @@ -1458,27 +1486,27 @@ EXPORT_SYMBOL(__breadahead); > * It returns NULL if the block was unreadable. > */ > struct buffer_head * > -__bread_gfp(struct block_device *bdev, sector_t block, > - unsigned size, gfp_t gfp) > +__bread_gfp(struct block_device *bdev, sector_t block, unsigned int size, > + gfp_t gfp) > { > - struct buffer_head *bh; > - > - gfp |= mapping_gfp_constraint(bdev->bd_inode->i_mapping, ~__GFP_FS); > - > - /* > - * Prefer looping in the allocator rather than here, at least that > - * code knows what it's doing. > - */ > - gfp |= __GFP_NOFAIL; > - > - bh = bdev_getblk(bdev, block, size, gfp); > - > - if (likely(bh) && !buffer_uptodate(bh)) > - bh = __bread_slow(bh); > - return bh; > + return bread_gfp(bdev, block, size, 0, gfp, false); > } > EXPORT_SYMBOL(__bread_gfp); > > +/* > + * This works like __bread_gfp() except: > + * 1) If buffer write failed before, set buffer uptodate and don't read > + * block from disk; > + * 2) Caller can pass in additional op_flags like REQ_META; > + */ > +struct buffer_head * > +__bread_gfp2(struct block_device *bdev, sector_t block, unsigned int size, > + blk_opf_t op_flags, gfp_t gfp) > +{ > + return bread_gfp(bdev, block, size, op_flags, gfp, true); > +} > +EXPORT_SYMBOL(__bread_gfp2); > + > static void __invalidate_bh_lrus(struct bh_lru *b) > { > int i; > diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h > index 5f23ee599889..751b2744b4ae 100644 > --- a/include/linux/buffer_head.h > +++ b/include/linux/buffer_head.h > @@ -171,6 +171,18 @@ static __always_inline int buffer_uptodate(const struct buffer_head *bh) > return test_bit_acquire(BH_Uptodate, &bh->b_state); > } > > +static __always_inline int buffer_uptodate_or_error(struct buffer_head *bh) > +{ > + /* > + * If the buffer has the write error flag, data was failed to write > + * out in the block. In this case, set buffer uptodate to prevent > + * reading old data. > + */ > + if (buffer_write_io_error(bh)) > + set_buffer_uptodate(bh); > + return buffer_uptodate(bh); > +} > + > static inline unsigned long bh_offset(const struct buffer_head *bh) > { > return (unsigned long)(bh)->b_data & (page_size(bh->b_page) - 1); > @@ -231,7 +243,11 @@ void __brelse(struct buffer_head *); > void __bforget(struct buffer_head *); > void __breadahead(struct block_device *, sector_t block, unsigned int size); > struct buffer_head *__bread_gfp(struct block_device *, > - sector_t block, unsigned size, gfp_t gfp); > + sector_t block, unsigned int size, gfp_t gfp); > +struct buffer_head *__bread_gfp2(struct block_device *bdev, sector_t block, > + unsigned int size, blk_opf_t op_flags, > + gfp_t gfp); > + > struct buffer_head *alloc_buffer_head(gfp_t gfp_flags); > void free_buffer_head(struct buffer_head * bh); > void unlock_buffer(struct buffer_head *bh); > -- > 2.39.2 > -- Jan Kara SUSE Labs, CR