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64K PAGE_SIZE compatibility #255

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64K PAGE_SIZE compatibility #255

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31 changes: 21 additions & 10 deletions src/dattobd.c
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Original file line number Diff line number Diff line change
Expand Up @@ -718,7 +718,7 @@ static inline void dattobd_bio_copy_dev(struct bio *dst, struct bio *src){

//macros for defining sector and block sizes
#define SECTORS_PER_PAGE (PAGE_SIZE / SECTOR_SIZE)
#define COW_SECTION_SIZE 4096
#define COW_SECTION_SIZE PAGE_SIZE
#define SECTORS_PER_BLOCK (COW_BLOCK_SIZE / SECTOR_SIZE)
#define SECTOR_TO_BLOCK(sect) ((sect) / SECTORS_PER_BLOCK)
#define BLOCK_TO_SECTOR(block) ((block) * SECTORS_PER_BLOCK)
Expand Down Expand Up @@ -2508,11 +2508,11 @@ static void bio_free_clone(struct bio *bio){
bio_put(bio);
}

static int bio_make_read_clone(struct bio_set *bs, struct tracing_params *tp, struct bio *orig_bio, sector_t sect, unsigned int pages, struct bio **bio_out, unsigned int *bytes_added){
static int bio_make_read_clone(struct bio_set *bs, struct tracing_params *tp, struct bio *orig_bio, sector_t sect, unsigned int pages, unsigned int tail, struct bio **bio_out, unsigned int *bytes_added){
int ret;
struct bio *new_bio;
struct page *pg;
unsigned int i, bytes, total = 0, actual_pages = (pages > BIO_MAX_PAGES)? BIO_MAX_PAGES : pages;
unsigned int i, bytes, actual_size = PAGE_SIZE, total = 0, actual_pages = (pages > BIO_MAX_PAGES)? BIO_MAX_PAGES : pages;

//allocate bio clone
new_bio = bio_alloc_bioset(GFP_NOIO, actual_pages, bs);
Expand Down Expand Up @@ -2545,9 +2545,13 @@ static int bio_make_read_clone(struct bio_set *bs, struct tracing_params *tp, st
goto error;
}

//only need to read actual_size data in last page when bio is no page aligned
if (i == pages - 1 && tail != 0) {
actual_size = PAGE_SIZE - tail;
}
//add the page to the bio
bytes = bio_add_page(new_bio, pg, PAGE_SIZE, 0);
if(bytes != PAGE_SIZE){
bytes = bio_add_page(new_bio, pg, actual_size, 0);
if(bytes != actual_size){
__free_page(pg);
break;
}
Expand Down Expand Up @@ -2937,7 +2941,12 @@ static void __on_bio_read_complete(struct bio *bio, int err){
#ifndef HAVE_BVEC_ITER
//#if LINUX_VERSION_CODE < KERNEL_VERSION(3,14,0)
for(i = 0; i < bio->bi_vcnt; i++){
bio->bi_io_vec[i].bv_len = PAGE_SIZE;
//last io_vec will less than a page when size is not page aligned, 64k pagesize e.g.
if ((i+1)*PAGE_SIZE > map->size) {
bio->bi_io_vec[i].bv_len = map->size - i * PAGE_SIZE;
} else {
bio->bi_io_vec[i].bv_len = PAGE_SIZE;
}
bio->bi_io_vec[i].bv_offset = 0;
}
#endif
Expand Down Expand Up @@ -2994,23 +3003,25 @@ static int snap_trace_bio(struct snap_device *dev, struct bio *bio){
struct bio *new_bio = NULL;
struct tracing_params *tp = NULL;
sector_t start_sect, end_sect;
unsigned int bytes, pages;
unsigned int bytes, pages, tail;

//if we don't need to cow this bio just call the real mrf normally
if(!bio_needs_cow(bio, dev->sd_cow_inode)) return dattobd_call_mrf(dev->sd_orig_mrf, dattobd_bio_get_queue(bio), bio);

//the cow manager works in 4096 byte blocks, so read clones must also be 4096 byte aligned
start_sect = ROUND_DOWN(bio_sector(bio) - dev->sd_sect_off, SECTORS_PER_BLOCK) + dev->sd_sect_off;
end_sect = ROUND_UP(bio_sector(bio) + (bio_size(bio) / SECTOR_SIZE) - dev->sd_sect_off, SECTORS_PER_BLOCK) + dev->sd_sect_off;
pages = (end_sect - start_sect) / SECTORS_PER_PAGE;
//end_sect - start_sect is not always page aligned, 64k pagesize e.g.
pages = ROUND_UP(end_sect - start_sect, SECTORS_PER_PAGE) / SECTORS_PER_PAGE;
tail = pages * PAGE_SIZE - (end_sect - start_sect) * SECTOR_SIZE;

//allocate tracing_params struct to hold all pointers we will need across contexts
ret = tp_alloc(dev, bio, &tp);
if(ret) goto error;

retry:
//allocate and populate read bio clone. This bio may not have all the pages we need due to queue restrictions
ret = bio_make_read_clone(dev_bioset(dev), tp, bio, start_sect, pages, &new_bio, &bytes);
ret = bio_make_read_clone(dev_bioset(dev), tp, bio, start_sect, pages, tail, &new_bio, &bytes);
if(ret) goto error;

//set pointers for read clone
Expand All @@ -3024,7 +3035,7 @@ static int snap_trace_bio(struct snap_device *dev, struct bio *bio){
dattobd_submit_bio(new_bio);

//if our bio didn't cover the entire clone we must keep creating bios until we have
if(bytes / PAGE_SIZE < pages){
if(bytes < (end_sect - start_sect) * SECTOR_SIZE){
start_sect += bytes / SECTOR_SIZE;
pages -= bytes / PAGE_SIZE;
goto retry;
Expand Down