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![Qu Wenruo](/assets/img/avatar_default.png)
For P/Q stripe scrub, we have quite some duplicated read IO: - Data stripes read for verification This is triggered by the scrub_submit_initial_read() inside scrub_raid56_parity_stripe(). - Data stripes read (again) for P/Q stripe verification This is triggered by scrub_assemble_read_bios() from scrub_rbio(). Although we can have hit rbio cache and avoid unnecessary read, the chance is very low, as scrub would easily flush the whole rbio cache. This means, even we're just scrubbing a single P/Q stripe, we would read the data stripes twice for the best case scenario. If we need to recover some data stripes, it would cause more reads on the same data stripes, again and again. However before we call raid56_parity_submit_scrub_rbio() we already have all data stripes repaired and their contents ready to use. But RAID56 cache is unaware about the scrub cache, thus RAID56 layer itself still needs to re-read the data stripes. To avoid such cache miss, this patch would: - Introduce a new helper, raid56_parity_cache_data_pages() This function would grab the pages from an array, and copy the content to the rbio, marking all the involved sectors uptodate. The page copy is unavoidable because of the cache pages of rbio are all self managed, thus can not utilize outside pages without screwing up the lifespan. - Use the repaired data stripes as cache inside scrub_raid56_parity_stripe() By this, we ensure all the data sectors of the scrub rbio are already uptodate, and no need to read them again from disk. Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
202 lines
5.2 KiB
C
202 lines
5.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Copyright (C) 2012 Fusion-io All rights reserved.
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* Copyright (C) 2012 Intel Corp. All rights reserved.
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*/
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#ifndef BTRFS_RAID56_H
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#define BTRFS_RAID56_H
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#include <linux/workqueue.h>
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#include "volumes.h"
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enum btrfs_rbio_ops {
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BTRFS_RBIO_WRITE,
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BTRFS_RBIO_READ_REBUILD,
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BTRFS_RBIO_PARITY_SCRUB,
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BTRFS_RBIO_REBUILD_MISSING,
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};
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struct btrfs_raid_bio {
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struct btrfs_io_context *bioc;
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/*
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* While we're doing RMW on a stripe we put it into a hash table so we
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* can lock the stripe and merge more rbios into it.
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*/
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struct list_head hash_list;
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/* LRU list for the stripe cache */
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struct list_head stripe_cache;
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/* For scheduling work in the helper threads */
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struct work_struct work;
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/*
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* bio_list and bio_list_lock are used to add more bios into the stripe
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* in hopes of avoiding the full RMW
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*/
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struct bio_list bio_list;
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spinlock_t bio_list_lock;
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/*
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* Also protected by the bio_list_lock, the plug list is used by the
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* plugging code to collect partial bios while plugged. The stripe
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* locking code also uses it to hand off the stripe lock to the next
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* pending IO.
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*/
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struct list_head plug_list;
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/* Flags that tell us if it is safe to merge with this bio. */
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unsigned long flags;
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/*
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* Set if we're doing a parity rebuild for a read from higher up, which
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* is handled differently from a parity rebuild as part of RMW.
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*/
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enum btrfs_rbio_ops operation;
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/* How many pages there are for the full stripe including P/Q */
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u16 nr_pages;
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/* How many sectors there are for the full stripe including P/Q */
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u16 nr_sectors;
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/* Number of data stripes (no p/q) */
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u8 nr_data;
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/* Number of all stripes (including P/Q) */
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u8 real_stripes;
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/* How many pages there are for each stripe */
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u8 stripe_npages;
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/* How many sectors there are for each stripe */
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u8 stripe_nsectors;
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/* Stripe number that we're scrubbing */
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u8 scrubp;
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/*
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* Size of all the bios in the bio_list. This helps us decide if the
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* rbio maps to a full stripe or not.
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*/
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int bio_list_bytes;
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refcount_t refs;
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atomic_t stripes_pending;
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wait_queue_head_t io_wait;
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/* Bitmap to record which horizontal stripe has data */
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unsigned long dbitmap;
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/* Allocated with stripe_nsectors-many bits for finish_*() calls */
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unsigned long finish_pbitmap;
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/*
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* These are two arrays of pointers. We allocate the rbio big enough
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* to hold them both and setup their locations when the rbio is
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* allocated.
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*/
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/*
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* Pointers to pages that we allocated for reading/writing stripes
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* directly from the disk (including P/Q).
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*/
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struct page **stripe_pages;
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/* Pointers to the sectors in the bio_list, for faster lookup */
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struct sector_ptr *bio_sectors;
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/*
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* For subpage support, we need to map each sector to above
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* stripe_pages.
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*/
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struct sector_ptr *stripe_sectors;
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/* Allocated with real_stripes-many pointers for finish_*() calls */
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void **finish_pointers;
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/*
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* The bitmap recording where IO errors happened.
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* Each bit is corresponding to one sector in either bio_sectors[] or
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* stripe_sectors[] array.
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*
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* The reason we don't use another bit in sector_ptr is, we have two
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* arrays of sectors, and a lot of IO can use sectors in both arrays.
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* Thus making it much harder to iterate.
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*/
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unsigned long *error_bitmap;
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/*
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* Checksum buffer if the rbio is for data. The buffer should cover
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* all data sectors (excluding P/Q sectors).
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*/
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u8 *csum_buf;
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/*
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* Each bit represents if the corresponding sector has data csum found.
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* Should only cover data sectors (excluding P/Q sectors).
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*/
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unsigned long *csum_bitmap;
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};
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/*
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* For trace event usage only. Records useful debug info for each bio submitted
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* by RAID56 to each physical device.
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*
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* No matter signed or not, (-1) is always the one indicating we can not grab
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* the proper stripe number.
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*/
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struct raid56_bio_trace_info {
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u64 devid;
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/* The offset inside the stripe. (<= STRIPE_LEN) */
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u32 offset;
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/*
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* Stripe number.
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* 0 is the first data stripe, and nr_data for P stripe,
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* nr_data + 1 for Q stripe.
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* >= real_stripes for
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*/
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u8 stripe_nr;
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};
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static inline int nr_data_stripes(const struct map_lookup *map)
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{
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return map->num_stripes - btrfs_nr_parity_stripes(map->type);
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}
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static inline int nr_bioc_data_stripes(const struct btrfs_io_context *bioc)
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{
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return bioc->num_stripes - btrfs_nr_parity_stripes(bioc->map_type);
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}
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#define RAID5_P_STRIPE ((u64)-2)
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#define RAID6_Q_STRIPE ((u64)-1)
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#define is_parity_stripe(x) (((x) == RAID5_P_STRIPE) || \
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((x) == RAID6_Q_STRIPE))
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struct btrfs_device;
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void raid56_parity_recover(struct bio *bio, struct btrfs_io_context *bioc,
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int mirror_num);
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void raid56_parity_write(struct bio *bio, struct btrfs_io_context *bioc);
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struct btrfs_raid_bio *raid56_parity_alloc_scrub_rbio(struct bio *bio,
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struct btrfs_io_context *bioc,
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struct btrfs_device *scrub_dev,
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unsigned long *dbitmap, int stripe_nsectors);
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void raid56_parity_submit_scrub_rbio(struct btrfs_raid_bio *rbio);
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void raid56_parity_cache_data_pages(struct btrfs_raid_bio *rbio,
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struct page **data_pages, u64 data_logical);
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int btrfs_alloc_stripe_hash_table(struct btrfs_fs_info *info);
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void btrfs_free_stripe_hash_table(struct btrfs_fs_info *info);
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#endif
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