![Christoph Hellwig](/assets/img/avatar_default.png)
Currently we have two different ways to signal an I/O error on a BIO: (1) by clearing the BIO_UPTODATE flag (2) by returning a Linux errno value to the bi_end_io callback The first one has the drawback of only communicating a single possible error (-EIO), and the second one has the drawback of not beeing persistent when bios are queued up, and are not passed along from child to parent bio in the ever more popular chaining scenario. Having both mechanisms available has the additional drawback of utterly confusing driver authors and introducing bugs where various I/O submitters only deal with one of them, and the others have to add boilerplate code to deal with both kinds of error returns. So add a new bi_error field to store an errno value directly in struct bio and remove the existing mechanisms to clean all this up. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Hannes Reinecke <hare@suse.de> Reviewed-by: NeilBrown <neilb@suse.com> Signed-off-by: Jens Axboe <axboe@fb.com>
290 lines
6.3 KiB
C
290 lines
6.3 KiB
C
/* bounce buffer handling for block devices
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*
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* - Split from highmem.c
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/mm.h>
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#include <linux/export.h>
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#include <linux/swap.h>
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#include <linux/gfp.h>
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#include <linux/bio.h>
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#include <linux/pagemap.h>
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#include <linux/mempool.h>
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#include <linux/blkdev.h>
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#include <linux/backing-dev.h>
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#include <linux/init.h>
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#include <linux/hash.h>
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#include <linux/highmem.h>
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#include <linux/bootmem.h>
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#include <linux/printk.h>
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#include <asm/tlbflush.h>
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#include <trace/events/block.h>
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#define POOL_SIZE 64
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#define ISA_POOL_SIZE 16
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static mempool_t *page_pool, *isa_page_pool;
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#if defined(CONFIG_HIGHMEM) || defined(CONFIG_NEED_BOUNCE_POOL)
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static __init int init_emergency_pool(void)
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{
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#if defined(CONFIG_HIGHMEM) && !defined(CONFIG_MEMORY_HOTPLUG)
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if (max_pfn <= max_low_pfn)
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return 0;
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#endif
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page_pool = mempool_create_page_pool(POOL_SIZE, 0);
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BUG_ON(!page_pool);
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pr_info("pool size: %d pages\n", POOL_SIZE);
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return 0;
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}
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__initcall(init_emergency_pool);
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#endif
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#ifdef CONFIG_HIGHMEM
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/*
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* highmem version, map in to vec
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*/
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static void bounce_copy_vec(struct bio_vec *to, unsigned char *vfrom)
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{
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unsigned long flags;
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unsigned char *vto;
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local_irq_save(flags);
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vto = kmap_atomic(to->bv_page);
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memcpy(vto + to->bv_offset, vfrom, to->bv_len);
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kunmap_atomic(vto);
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local_irq_restore(flags);
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}
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#else /* CONFIG_HIGHMEM */
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#define bounce_copy_vec(to, vfrom) \
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memcpy(page_address((to)->bv_page) + (to)->bv_offset, vfrom, (to)->bv_len)
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#endif /* CONFIG_HIGHMEM */
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/*
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* allocate pages in the DMA region for the ISA pool
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*/
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static void *mempool_alloc_pages_isa(gfp_t gfp_mask, void *data)
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{
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return mempool_alloc_pages(gfp_mask | GFP_DMA, data);
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}
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/*
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* gets called "every" time someone init's a queue with BLK_BOUNCE_ISA
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* as the max address, so check if the pool has already been created.
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*/
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int init_emergency_isa_pool(void)
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{
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if (isa_page_pool)
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return 0;
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isa_page_pool = mempool_create(ISA_POOL_SIZE, mempool_alloc_pages_isa,
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mempool_free_pages, (void *) 0);
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BUG_ON(!isa_page_pool);
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pr_info("isa pool size: %d pages\n", ISA_POOL_SIZE);
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return 0;
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}
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/*
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* Simple bounce buffer support for highmem pages. Depending on the
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* queue gfp mask set, *to may or may not be a highmem page. kmap it
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* always, it will do the Right Thing
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*/
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static void copy_to_high_bio_irq(struct bio *to, struct bio *from)
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{
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unsigned char *vfrom;
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struct bio_vec tovec, *fromvec = from->bi_io_vec;
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struct bvec_iter iter;
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bio_for_each_segment(tovec, to, iter) {
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if (tovec.bv_page != fromvec->bv_page) {
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/*
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* fromvec->bv_offset and fromvec->bv_len might have
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* been modified by the block layer, so use the original
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* copy, bounce_copy_vec already uses tovec->bv_len
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*/
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vfrom = page_address(fromvec->bv_page) +
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tovec.bv_offset;
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bounce_copy_vec(&tovec, vfrom);
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flush_dcache_page(tovec.bv_page);
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}
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fromvec++;
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}
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}
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static void bounce_end_io(struct bio *bio, mempool_t *pool)
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{
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struct bio *bio_orig = bio->bi_private;
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struct bio_vec *bvec, *org_vec;
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int i;
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/*
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* free up bounce indirect pages used
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*/
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bio_for_each_segment_all(bvec, bio, i) {
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org_vec = bio_orig->bi_io_vec + i;
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if (bvec->bv_page == org_vec->bv_page)
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continue;
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dec_zone_page_state(bvec->bv_page, NR_BOUNCE);
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mempool_free(bvec->bv_page, pool);
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}
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bio_orig->bi_error = bio->bi_error;
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bio_endio(bio_orig);
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bio_put(bio);
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}
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static void bounce_end_io_write(struct bio *bio)
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{
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bounce_end_io(bio, page_pool);
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}
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static void bounce_end_io_write_isa(struct bio *bio)
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{
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bounce_end_io(bio, isa_page_pool);
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}
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static void __bounce_end_io_read(struct bio *bio, mempool_t *pool)
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{
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struct bio *bio_orig = bio->bi_private;
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if (!bio->bi_error)
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copy_to_high_bio_irq(bio_orig, bio);
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bounce_end_io(bio, pool);
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}
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static void bounce_end_io_read(struct bio *bio)
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{
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__bounce_end_io_read(bio, page_pool);
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}
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static void bounce_end_io_read_isa(struct bio *bio)
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{
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__bounce_end_io_read(bio, isa_page_pool);
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}
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#ifdef CONFIG_NEED_BOUNCE_POOL
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static int must_snapshot_stable_pages(struct request_queue *q, struct bio *bio)
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{
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if (bio_data_dir(bio) != WRITE)
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return 0;
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if (!bdi_cap_stable_pages_required(&q->backing_dev_info))
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return 0;
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return test_bit(BIO_SNAP_STABLE, &bio->bi_flags);
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}
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#else
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static int must_snapshot_stable_pages(struct request_queue *q, struct bio *bio)
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{
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return 0;
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}
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#endif /* CONFIG_NEED_BOUNCE_POOL */
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static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
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mempool_t *pool, int force)
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{
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struct bio *bio;
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int rw = bio_data_dir(*bio_orig);
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struct bio_vec *to, from;
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struct bvec_iter iter;
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unsigned i;
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if (force)
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goto bounce;
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bio_for_each_segment(from, *bio_orig, iter)
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if (page_to_pfn(from.bv_page) > queue_bounce_pfn(q))
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goto bounce;
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return;
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bounce:
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bio = bio_clone_bioset(*bio_orig, GFP_NOIO, fs_bio_set);
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bio_for_each_segment_all(to, bio, i) {
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struct page *page = to->bv_page;
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if (page_to_pfn(page) <= queue_bounce_pfn(q) && !force)
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continue;
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to->bv_page = mempool_alloc(pool, q->bounce_gfp);
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inc_zone_page_state(to->bv_page, NR_BOUNCE);
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if (rw == WRITE) {
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char *vto, *vfrom;
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flush_dcache_page(page);
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vto = page_address(to->bv_page) + to->bv_offset;
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vfrom = kmap_atomic(page) + to->bv_offset;
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memcpy(vto, vfrom, to->bv_len);
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kunmap_atomic(vfrom);
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}
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}
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trace_block_bio_bounce(q, *bio_orig);
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bio->bi_flags |= (1 << BIO_BOUNCED);
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if (pool == page_pool) {
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bio->bi_end_io = bounce_end_io_write;
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if (rw == READ)
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bio->bi_end_io = bounce_end_io_read;
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} else {
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bio->bi_end_io = bounce_end_io_write_isa;
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if (rw == READ)
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bio->bi_end_io = bounce_end_io_read_isa;
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}
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bio->bi_private = *bio_orig;
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*bio_orig = bio;
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}
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void blk_queue_bounce(struct request_queue *q, struct bio **bio_orig)
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{
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int must_bounce;
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mempool_t *pool;
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/*
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* Data-less bio, nothing to bounce
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*/
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if (!bio_has_data(*bio_orig))
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return;
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must_bounce = must_snapshot_stable_pages(q, *bio_orig);
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/*
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* for non-isa bounce case, just check if the bounce pfn is equal
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* to or bigger than the highest pfn in the system -- in that case,
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* don't waste time iterating over bio segments
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*/
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if (!(q->bounce_gfp & GFP_DMA)) {
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if (queue_bounce_pfn(q) >= blk_max_pfn && !must_bounce)
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return;
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pool = page_pool;
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} else {
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BUG_ON(!isa_page_pool);
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pool = isa_page_pool;
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}
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/*
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* slow path
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*/
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__blk_queue_bounce(q, bio_orig, pool, must_bounce);
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}
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EXPORT_SYMBOL(blk_queue_bounce);
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