diff options
Diffstat (limited to 'fs/btrfs/raid56.h')
| -rw-r--r-- | fs/btrfs/raid56.h | 103 |
1 files changed, 92 insertions, 11 deletions
diff --git a/fs/btrfs/raid56.h b/fs/btrfs/raid56.h index 84c4d1d29c7a..1f463ecf7e41 100644 --- a/fs/btrfs/raid56.h +++ b/fs/btrfs/raid56.h @@ -16,7 +16,6 @@ #include "volumes.h" struct page; -struct sector_ptr; struct btrfs_fs_info; enum btrfs_rbio_ops { @@ -25,6 +24,84 @@ enum btrfs_rbio_ops { BTRFS_RBIO_PARITY_SCRUB, }; +/* + * Overview of btrfs_raid_bio. + * + * One btrfs_raid_bio represents a full stripe of RAID56, including both data + * and P/Q stripes. For now, each data and P/Q stripe is of a fixed length (64K). + * + * One btrfs_raid_bio can have one or more bios from higher layer, covering + * part or all of the data stripes. + * + * [PAGES FROM HIGHER LAYER BIOS] + * Higher layer bios are in the btrfs_raid_bio::bio_list. + * + * Pages from the bio_list are represented like the following: + * + * bio_list: |<- Bio 1 ->| |<- Bio 2 ->| ... + * bio_paddrs: [0] [1] [2] [3] [4] [5] ... + * + * If there is a bio covering a sector (one btrfs fs block), the corresponding + * pointer in btrfs_raid_bio::bio_paddrs[] will point to the physical address + * (with the offset inside the page) of the corresponding bio. + * + * If there is no bio covering a sector, then btrfs_raid_bio::bio_paddrs[i] will + * be INVALID_PADDR. + * + * The length of each entry in bio_paddrs[] is a step (aka, min(sectorsize, PAGE_SIZE)). + * + * [PAGES FOR INTERNAL USAGES] + * Pages not covered by any bio or belonging to P/Q stripes are stored in + * btrfs_raid_bio::stripe_pages[] and stripe_paddrs[], like the following: + * + * stripe_pages: |<- Page 0 ->|<- Page 1 ->| ... + * stripe_paddrs: [0] [1] [2] [3] [4] ... + * + * stripe_pages[] array stores all the pages covering the full stripe, including + * data and P/Q pages. + * stripe_pages[0] is the first page of the first data stripe. + * stripe_pages[BTRFS_STRIPE_LEN / PAGE_SIZE] is the first page of the second + * data stripe. + * + * Some pointers inside stripe_pages[] can be NULL, e.g. for a full stripe write + * (the bio covers all data stripes) there is no need to allocate pages for + * data stripes (can grab from bio_paddrs[]). + * + * If the corresponding page of stripe_paddrs[i] is not allocated, the value of + * stripe_paddrs[i] will be INVALID_PADDR. + * + * The length of each entry in stripe_paddrs[] is a step. + * + * [LOCATING A SECTOR] + * To locate a sector for IO, we need the following info: + * + * - stripe_nr + * Starts from 0 (representing the first data stripe), ends at + * @nr_data (RAID5, P stripe) or @nr_data + 1 (RAID6, Q stripe). + * + * - sector_nr + * Starts from 0 (representing the first sector of the stripe), ends + * at BTRFS_STRIPE_LEN / sectorsize - 1. + * + * - step_nr + * A step is min(sector_size, PAGE_SIZE). + * + * Starts from 0 (representing the first step of the sector), ends + * at @sector_nsteps - 1. + * + * For most call sites they do not need to bother this parameter. + * It is for bs > ps support and only for vertical stripe related works. + * (e.g. RMW/recover) + * + * - from which array + * Whether grabbing from stripe_paddrs[] (aka, internal pages) or from the + * bio_paddrs[] (aka, from the higher layer bios). + * + * For IO, a physical address is returned, so that we can extract the page and + * the offset inside the page for IO. + * A special value INVALID_PADDR represents when the physical address is invalid, + * normally meaning there is no page allocated for the specified sector. + */ struct btrfs_raid_bio { struct btrfs_io_context *bioc; @@ -82,6 +159,14 @@ struct btrfs_raid_bio { /* How many sectors there are for each stripe */ u8 stripe_nsectors; + /* + * How many steps there are for one sector. + * + * For bs > ps cases, it's sectorsize / PAGE_SIZE. + * For bs <= ps cases, it's always 1. + */ + u8 sector_nsteps; + /* Stripe number that we're scrubbing */ u8 scrubp; @@ -116,13 +201,13 @@ struct btrfs_raid_bio { struct page **stripe_pages; /* Pointers to the sectors in the bio_list, for faster lookup */ - struct sector_ptr *bio_sectors; + phys_addr_t *bio_paddrs; - /* - * For subpage support, we need to map each sector to above - * stripe_pages. - */ - struct sector_ptr *stripe_sectors; + /* Pointers to the sectors in the stripe_pages[]. */ + phys_addr_t *stripe_paddrs; + + /* Each set bit means the corresponding sector in stripe_sectors[] is uptodate. */ + unsigned long *stripe_uptodate_bitmap; /* Allocated with real_stripes-many pointers for finish_*() calls */ void **finish_pointers; @@ -131,10 +216,6 @@ struct btrfs_raid_bio { * The bitmap recording where IO errors happened. * Each bit is corresponding to one sector in either bio_sectors[] or * stripe_sectors[] array. - * - * The reason we don't use another bit in sector_ptr is, we have two - * arrays of sectors, and a lot of IO can use sectors in both arrays. - * Thus making it much harder to iterate. */ unsigned long *error_bitmap; |