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Changed tracing params bio_sects to a list
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With multipage bio, it keeps overflowing, which we catch and then error.
Now, we'll dynamically allocate bio_sector_maps and never overflow
(until we run out of memory).
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@dakotarwilliams @Conan-Kudo
dakotarwilliams authored and Conan-Kudo committed Sep 21, 2020
1 parent 1a5b812 commit 9a15da2
Showing 1 changed file with 52 additions and 26 deletions.
78 changes: 52 additions & 26 deletions src/dattobd.c
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Original file line number Diff line number Diff line change
Expand Up @@ -723,9 +723,6 @@ static inline void dattobd_bio_copy_dev(struct bio *dst, struct bio *src){
#define SECTOR_TO_BLOCK(sect) ((sect) / SECTORS_PER_BLOCK)
#define BLOCK_TO_SECTOR(block) ((block) * SECTORS_PER_BLOCK)

//maximum number of clones per traced bio
#define MAX_CLONES_PER_BIO 10

//macros for compilation
#define MAYBE_UNUSED(x) (void)(x)

Expand Down Expand Up @@ -808,13 +805,19 @@ struct bio_sector_map{
struct bio *bio;
sector_t sect;
unsigned int size;
struct bio_sector_map *next;
};

struct bsector_list {
struct bio_sector_map* head;
struct bio_sector_map* tail;
};

struct tracing_params{
struct bio *orig_bio;
struct snap_device *dev;
atomic_t refs;
struct bio_sector_map bio_sects[MAX_CLONES_PER_BIO];
struct bsector_list bio_sects;
};

struct cow_section{
Expand Down Expand Up @@ -2399,6 +2402,8 @@ static int tp_alloc(struct snap_device *dev, struct bio *bio, struct tracing_par

tp->dev = dev;
tp->orig_bio = bio;
tp->bio_sects.head = NULL;
tp->bio_sects.tail = NULL;
atomic_set(&tp->refs, 1);

*tp_out = tp;
Expand All @@ -2412,12 +2417,44 @@ static void tp_get(struct tracing_params *tp){
static void tp_put(struct tracing_params *tp){
//drop a reference to the tp
if(atomic_dec_and_test(&tp->refs)){
struct bio_sector_map *next, *curr = NULL;

//if there are no references left, its safe to release the orig_bio
bio_queue_add(&tp->dev->sd_orig_bios, tp->orig_bio);

// free nodes in the sector map list
for (curr = tp->bio_sects.head; curr != NULL; curr = next)
{
next = curr->next;
kfree(curr);
}
kfree(tp);
}
}

static int tp_add(struct tracing_params* tp, struct bio* bio) {
struct bio_sector_map* map;
map = kzalloc(1 * sizeof(struct bio_sector_map), GFP_NOIO);
if (!map) {
LOG_ERROR(-ENOMEM, "error allocating new bio_sector_map struct");
return -ENOMEM;
}

map->bio = bio;
map->sect = bio_sector(bio);
map->size = bio_size(bio);
map->next = NULL;
if (tp->bio_sects.head == NULL) {
tp->bio_sects.head = map;
tp->bio_sects.tail = map;
}
else {
tp->bio_sects.tail->next = map;
tp->bio_sects.tail = map;
}
return 0;
}

/****************************BIO HELPER FUNCTIONS*****************************/

static inline struct inode *page_get_inode(struct page *pg){
Expand Down Expand Up @@ -2866,9 +2903,12 @@ static int inc_sset_thread(void *data){

static void __on_bio_read_complete(struct bio *bio, int err){
int ret;
unsigned short i;
struct tracing_params *tp = bio->bi_private;
struct snap_device *dev = tp->dev;
struct bio_sector_map* map = NULL;
#ifndef HAVE_BVEC_ITER
unsigned short i = 0;
#endif

//check for read errors
if(err){
Expand All @@ -2881,21 +2921,15 @@ static void __on_bio_read_complete(struct bio *bio, int err){
dattobd_set_bio_ops(bio, REQ_OP_WRITE, 0);

//reset the bio iterator to its original state
for(i = 0; i < MAX_CLONES_PER_BIO && tp->bio_sects[i].bio != NULL; i++){
if(bio == tp->bio_sects[i].bio){
bio_sector(bio) = tp->bio_sects[i].sect - dev->sd_sect_off;
bio_size(bio) = tp->bio_sects[i].size;
for(map = tp->bio_sects.head; map != NULL && map->bio != NULL; map = map->next) {
if(bio == map->bio){
bio_sector(bio) = map->sect - dev->sd_sect_off;
bio_size(bio) = map->size;
bio_idx(bio) = 0;
break;
}
}

if(i == MAX_CLONES_PER_BIO){
ret = -EIO;
LOG_ERROR(ret, "clone not found in tp struct");
goto error;
}

/*
* Reset the position in each bvec. Unnecessary with bvec iterators. Will cause multipage bvec capable kernels to
* lock up.
Expand Down Expand Up @@ -2960,7 +2994,7 @@ 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, i = 0;
unsigned int bytes, pages;

//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);
Expand All @@ -2979,16 +3013,9 @@ static int snap_trace_bio(struct snap_device *dev, struct bio *bio){
ret = bio_make_read_clone(dev_bioset(dev), tp, bio, start_sect, pages, &new_bio, &bytes);
if(ret) goto error;

//make sure we don't excede the max number of bio clones that tp can hold
if(i >= MAX_CLONES_PER_BIO){
ret = -EFAULT;
goto error;
}

//set pointers for read clone
tp->bio_sects[i].bio = new_bio;
tp->bio_sects[i].sect = bio_sector(new_bio);
tp->bio_sects[i].size = bio_size(new_bio);
ret = tp_add(tp, bio);
if (ret) goto error;

atomic64_inc(&dev->sd_submitted_cnt);
smp_wmb();
Expand All @@ -3000,7 +3027,6 @@ static int snap_trace_bio(struct snap_device *dev, struct bio *bio){
if(bytes / PAGE_SIZE < pages){
start_sect += bytes / SECTOR_SIZE;
pages -= bytes / PAGE_SIZE;
i++;
goto retry;
}

Expand Down

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