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9f0bbd8ca7
The block device driver puts a limit on maximum number of pages that
can be sent with the bio. Not all block devices can handle
BIO_MAX_PAGES number of pages in bio. Specifically the virtio-blk
diriver limits it to 126. When the LogFS file system was excersized in
KVM, the following bug from do_virtblk_request() was observed
static void do_virtblk_request(struct request_queue *q)
{
....
....
while ((req = blk_peek_request(q)) != NULL) {
BUG_ON(req->nr_phys_segments + 2 > vblk->sg_elems);
....
....
}
....
}
The patch fixes the problem by querring the maximum number of pages in
bio allowed from block device driver and then using those many pages
during submit_bio.
Signed-off-by: Prasad Joshi <prasadjoshi.linux@gmail.com>
342 lines
8.3 KiB
C
342 lines
8.3 KiB
C
/*
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* fs/logfs/dev_bdev.c - Device access methods for block devices
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*
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* As should be obvious for Linux kernel code, license is GPLv2
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*
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* Copyright (c) 2005-2008 Joern Engel <joern@logfs.org>
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*/
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#include "logfs.h"
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#include <linux/bio.h>
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#include <linux/blkdev.h>
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#include <linux/buffer_head.h>
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#include <linux/gfp.h>
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#include <linux/prefetch.h>
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#define PAGE_OFS(ofs) ((ofs) & (PAGE_SIZE-1))
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static void request_complete(struct bio *bio, int err)
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{
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complete((struct completion *)bio->bi_private);
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}
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static int sync_request(struct page *page, struct block_device *bdev, int rw)
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{
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struct bio bio;
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struct bio_vec bio_vec;
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struct completion complete;
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bio_init(&bio);
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bio.bi_max_vecs = 1;
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bio.bi_io_vec = &bio_vec;
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bio_vec.bv_page = page;
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bio_vec.bv_len = PAGE_SIZE;
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bio_vec.bv_offset = 0;
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bio.bi_vcnt = 1;
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bio.bi_idx = 0;
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bio.bi_size = PAGE_SIZE;
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bio.bi_bdev = bdev;
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bio.bi_sector = page->index * (PAGE_SIZE >> 9);
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init_completion(&complete);
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bio.bi_private = &complete;
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bio.bi_end_io = request_complete;
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submit_bio(rw, &bio);
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wait_for_completion(&complete);
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return test_bit(BIO_UPTODATE, &bio.bi_flags) ? 0 : -EIO;
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}
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static int bdev_readpage(void *_sb, struct page *page)
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{
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struct super_block *sb = _sb;
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struct block_device *bdev = logfs_super(sb)->s_bdev;
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int err;
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err = sync_request(page, bdev, READ);
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if (err) {
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ClearPageUptodate(page);
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SetPageError(page);
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} else {
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SetPageUptodate(page);
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ClearPageError(page);
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}
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unlock_page(page);
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return err;
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}
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static DECLARE_WAIT_QUEUE_HEAD(wq);
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static void writeseg_end_io(struct bio *bio, int err)
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{
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const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
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struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
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struct super_block *sb = bio->bi_private;
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struct logfs_super *super = logfs_super(sb);
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struct page *page;
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BUG_ON(!uptodate); /* FIXME: Retry io or write elsewhere */
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BUG_ON(err);
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BUG_ON(bio->bi_vcnt == 0);
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do {
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page = bvec->bv_page;
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if (--bvec >= bio->bi_io_vec)
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prefetchw(&bvec->bv_page->flags);
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end_page_writeback(page);
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page_cache_release(page);
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} while (bvec >= bio->bi_io_vec);
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bio_put(bio);
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if (atomic_dec_and_test(&super->s_pending_writes))
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wake_up(&wq);
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}
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static int __bdev_writeseg(struct super_block *sb, u64 ofs, pgoff_t index,
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size_t nr_pages)
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{
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struct logfs_super *super = logfs_super(sb);
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struct address_space *mapping = super->s_mapping_inode->i_mapping;
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struct bio *bio;
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struct page *page;
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unsigned int max_pages;
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int i;
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max_pages = min(nr_pages, (size_t) bio_get_nr_vecs(super->s_bdev));
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bio = bio_alloc(GFP_NOFS, max_pages);
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BUG_ON(!bio);
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for (i = 0; i < nr_pages; i++) {
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if (i >= max_pages) {
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/* Block layer cannot split bios :( */
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bio->bi_vcnt = i;
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bio->bi_idx = 0;
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bio->bi_size = i * PAGE_SIZE;
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bio->bi_bdev = super->s_bdev;
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bio->bi_sector = ofs >> 9;
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bio->bi_private = sb;
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bio->bi_end_io = writeseg_end_io;
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atomic_inc(&super->s_pending_writes);
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submit_bio(WRITE, bio);
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ofs += i * PAGE_SIZE;
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index += i;
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nr_pages -= i;
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i = 0;
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bio = bio_alloc(GFP_NOFS, max_pages);
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BUG_ON(!bio);
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}
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page = find_lock_page(mapping, index + i);
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BUG_ON(!page);
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bio->bi_io_vec[i].bv_page = page;
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bio->bi_io_vec[i].bv_len = PAGE_SIZE;
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bio->bi_io_vec[i].bv_offset = 0;
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BUG_ON(PageWriteback(page));
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set_page_writeback(page);
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unlock_page(page);
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}
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bio->bi_vcnt = nr_pages;
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bio->bi_idx = 0;
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bio->bi_size = nr_pages * PAGE_SIZE;
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bio->bi_bdev = super->s_bdev;
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bio->bi_sector = ofs >> 9;
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bio->bi_private = sb;
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bio->bi_end_io = writeseg_end_io;
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atomic_inc(&super->s_pending_writes);
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submit_bio(WRITE, bio);
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return 0;
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}
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static void bdev_writeseg(struct super_block *sb, u64 ofs, size_t len)
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{
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struct logfs_super *super = logfs_super(sb);
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int head;
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BUG_ON(super->s_flags & LOGFS_SB_FLAG_RO);
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if (len == 0) {
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/* This can happen when the object fit perfectly into a
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* segment, the segment gets written per sync and subsequently
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* closed.
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*/
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return;
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}
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head = ofs & (PAGE_SIZE - 1);
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if (head) {
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ofs -= head;
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len += head;
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}
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len = PAGE_ALIGN(len);
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__bdev_writeseg(sb, ofs, ofs >> PAGE_SHIFT, len >> PAGE_SHIFT);
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}
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static void erase_end_io(struct bio *bio, int err)
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{
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const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
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struct super_block *sb = bio->bi_private;
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struct logfs_super *super = logfs_super(sb);
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BUG_ON(!uptodate); /* FIXME: Retry io or write elsewhere */
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BUG_ON(err);
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BUG_ON(bio->bi_vcnt == 0);
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bio_put(bio);
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if (atomic_dec_and_test(&super->s_pending_writes))
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wake_up(&wq);
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}
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static int do_erase(struct super_block *sb, u64 ofs, pgoff_t index,
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size_t nr_pages)
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{
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struct logfs_super *super = logfs_super(sb);
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struct bio *bio;
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unsigned int max_pages;
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int i;
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max_pages = min(nr_pages, (size_t) bio_get_nr_vecs(super->s_bdev));
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bio = bio_alloc(GFP_NOFS, max_pages);
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BUG_ON(!bio);
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for (i = 0; i < nr_pages; i++) {
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if (i >= max_pages) {
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/* Block layer cannot split bios :( */
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bio->bi_vcnt = i;
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bio->bi_idx = 0;
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bio->bi_size = i * PAGE_SIZE;
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bio->bi_bdev = super->s_bdev;
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bio->bi_sector = ofs >> 9;
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bio->bi_private = sb;
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bio->bi_end_io = erase_end_io;
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atomic_inc(&super->s_pending_writes);
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submit_bio(WRITE, bio);
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ofs += i * PAGE_SIZE;
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index += i;
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nr_pages -= i;
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i = 0;
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bio = bio_alloc(GFP_NOFS, max_pages);
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BUG_ON(!bio);
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}
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bio->bi_io_vec[i].bv_page = super->s_erase_page;
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bio->bi_io_vec[i].bv_len = PAGE_SIZE;
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bio->bi_io_vec[i].bv_offset = 0;
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}
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bio->bi_vcnt = nr_pages;
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bio->bi_idx = 0;
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bio->bi_size = nr_pages * PAGE_SIZE;
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bio->bi_bdev = super->s_bdev;
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bio->bi_sector = ofs >> 9;
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bio->bi_private = sb;
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bio->bi_end_io = erase_end_io;
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atomic_inc(&super->s_pending_writes);
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submit_bio(WRITE, bio);
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return 0;
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}
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static int bdev_erase(struct super_block *sb, loff_t to, size_t len,
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int ensure_write)
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{
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struct logfs_super *super = logfs_super(sb);
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BUG_ON(to & (PAGE_SIZE - 1));
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BUG_ON(len & (PAGE_SIZE - 1));
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if (super->s_flags & LOGFS_SB_FLAG_RO)
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return -EROFS;
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if (ensure_write) {
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/*
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* Object store doesn't care whether erases happen or not.
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* But for the journal they are required. Otherwise a scan
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* can find an old commit entry and assume it is the current
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* one, travelling back in time.
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*/
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do_erase(sb, to, to >> PAGE_SHIFT, len >> PAGE_SHIFT);
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}
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return 0;
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}
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static void bdev_sync(struct super_block *sb)
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{
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struct logfs_super *super = logfs_super(sb);
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wait_event(wq, atomic_read(&super->s_pending_writes) == 0);
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}
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static struct page *bdev_find_first_sb(struct super_block *sb, u64 *ofs)
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{
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struct logfs_super *super = logfs_super(sb);
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struct address_space *mapping = super->s_mapping_inode->i_mapping;
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filler_t *filler = bdev_readpage;
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*ofs = 0;
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return read_cache_page(mapping, 0, filler, sb);
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}
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static struct page *bdev_find_last_sb(struct super_block *sb, u64 *ofs)
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{
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struct logfs_super *super = logfs_super(sb);
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struct address_space *mapping = super->s_mapping_inode->i_mapping;
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filler_t *filler = bdev_readpage;
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u64 pos = (super->s_bdev->bd_inode->i_size & ~0xfffULL) - 0x1000;
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pgoff_t index = pos >> PAGE_SHIFT;
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*ofs = pos;
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return read_cache_page(mapping, index, filler, sb);
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}
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static int bdev_write_sb(struct super_block *sb, struct page *page)
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{
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struct block_device *bdev = logfs_super(sb)->s_bdev;
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/* Nothing special to do for block devices. */
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return sync_request(page, bdev, WRITE);
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}
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static void bdev_put_device(struct logfs_super *s)
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{
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blkdev_put(s->s_bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
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}
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static int bdev_can_write_buf(struct super_block *sb, u64 ofs)
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{
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return 0;
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}
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static const struct logfs_device_ops bd_devops = {
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.find_first_sb = bdev_find_first_sb,
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.find_last_sb = bdev_find_last_sb,
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.write_sb = bdev_write_sb,
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.readpage = bdev_readpage,
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.writeseg = bdev_writeseg,
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.erase = bdev_erase,
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.can_write_buf = bdev_can_write_buf,
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.sync = bdev_sync,
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.put_device = bdev_put_device,
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};
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int logfs_get_sb_bdev(struct logfs_super *p, struct file_system_type *type,
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const char *devname)
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{
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struct block_device *bdev;
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bdev = blkdev_get_by_path(devname, FMODE_READ|FMODE_WRITE|FMODE_EXCL,
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type);
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if (IS_ERR(bdev))
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return PTR_ERR(bdev);
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if (MAJOR(bdev->bd_dev) == MTD_BLOCK_MAJOR) {
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int mtdnr = MINOR(bdev->bd_dev);
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blkdev_put(bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
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return logfs_get_sb_mtd(p, mtdnr);
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}
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p->s_bdev = bdev;
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p->s_mtd = NULL;
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p->s_devops = &bd_devops;
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return 0;
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}
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