/*
* This is the worker routine which does all the work of mapping the disk
* blocks and constructs largest possible bios, submits them for IO if the
* blocks are not contiguous on the disk.
*
* We pass a buffer_head back and forth and use its buffer_mapped() flag to
* represent the validity of its disk mapping and to decide when to do the next
* get_block() call.
*/
static struct bio *
do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,
sector_t *last_block_in_bio, struct buffer_head *map_bh,
unsigned long *first_logical_block, get_block_t get_block)
{
struct inode *inode = page->mapping->host;
const unsigned blkbits = inode->i_blkbits;
const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits;
const unsigned blocksize = 1 << blkbits;
sector_t block_in_file;
sector_t last_block;
sector_t last_block_in_file;
sector_t blocks[MAX_BUF_PER_PAGE];
unsigned page_block;
unsigned first_hole = blocks_per_page;
struct block_device *bdev = NULL;
int length;
int fully_mapped = 1;
unsigned nblocks;
unsigned relative_block;
if (page_has_buffers(page))
goto confused;
block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
last_block = block_in_file + nr_pages * blocks_per_page;
last_block_in_file = (i_size_read(inode) + blocksize - 1) >> blkbits;
if (last_block > last_block_in_file)
last_block = last_block_in_file;
page_block = 0;
/*
* Map blocks using the result from the previous get_blocks call first.
*/
nblocks = map_bh->b_size >> blkbits;
if (buffer_mapped(map_bh) && block_in_file > *first_logical_block &&
block_in_file < (*first_logical_block + nblocks)) {
unsigned map_offset = block_in_file - *first_logical_block;
unsigned last = nblocks - map_offset;
for (relative_block = 0; ; relative_block++) {
if (relative_block == last) {
clear_buffer_mapped(map_bh);
break;
}
if (page_block == blocks_per_page)
break;
blocks[page_block] = map_bh->b_blocknr + map_offset +
relative_block;
page_block++;
block_in_file++;
}
bdev = map_bh->b_bdev;
}
/*
* Then do more get_blocks calls until we are done with this page.
*/
map_bh->b_page = page;
while (page_block < blocks_per_page) {
map_bh->b_state = 0;
map_bh->b_size = 0;
if (block_in_file < last_block) {
map_bh->b_size = (last_block-block_in_file) << blkbits;
if (get_block(inode, block_in_file, map_bh, 0))
goto confused;
*first_logical_block = block_in_file;
}
if (!buffer_mapped(map_bh)) {
fully_mapped = 0;
if (first_hole == blocks_per_page)
first_hole = page_block;
page_block++;
block_in_file++;
continue;
}
/* some filesystems will copy data into the page during
* the get_block call, in which case we don't want to
* read it again. map_buffer_to_page copies the data
* we just collected from get_block into the page's buffers
* so readpage doesn't have to repeat the get_block call
*/
if (buffer_uptodate(map_bh)) {
map_buffer_to_page(page, map_bh, page_block);
goto confused;
}
if (first_hole != blocks_per_page)
goto confused; /* hole -> non-hole */
/* Contiguous blocks? */
if (page_block && blocks[page_block-1] != map_bh->b_blocknr-1)
goto confused;
nblocks = map_bh->b_size >> blkbits;
for (relative_block = 0; ; relative_block++) {
if (relative_block == nblocks) {
clear_buffer_mapped(map_bh);
break;
} else if (page_block == blocks_per_page)
break;
blocks[page_block] = map_bh->b_blocknr+relative_block;
page_block++;
block_in_file++;
}
bdev = map_bh->b_bdev;
}
if (first_hole != blocks_per_page) {
zero_user_segment(page, first_hole << blkbits, PAGE_CACHE_SIZE);
if (first_hole == 0) {
SetPageUptodate(page);
unlock_page(page);
goto out;
}
} else if (fully_mapped) {
SetPageMappedToDisk(page);
}
if (fully_mapped && blocks_per_page == 1 && !PageUptodate(page) &&
cleancache_get_page(page) == 0) {
SetPageUptodate(page);
goto confused;
}
/*
* This page will go to BIO. Do we need to send this BIO off first?
*/
if (bio && (*last_block_in_bio != blocks[0] - 1))
bio = mpage_bio_submit(READ, bio);
alloc_new:
if (bio == NULL) {
bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
min_t(int, nr_pages, bio_get_nr_vecs(bdev)),
GFP_KERNEL);
if (bio == NULL)
goto confused;
}
/*
* This is the worker routine which does all the work of mapping the disk
* blocks and constructs largest possible bios, submits them for IO if the
* blocks are not contiguous on the disk.
*
* We pass a buffer_head back and forth and use its buffer_mapped() flag to
* represent the validity of its disk mapping and to decide when to do the next
* get_block() call.
*/
static struct bio *
do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,
sector_t *last_block_in_bio, struct buffer_head *map_bh,
unsigned long *first_logical_block, struct compressed_bio **cb, get_block_t get_block)
{
struct inode *inode = page->mapping->host;
const unsigned blkbits = inode->i_blkbits;
const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits; //SET TO 1
const unsigned blocksize = 1 << blkbits;
sector_t block_in_file;
sector_t last_block;
sector_t last_block_in_file;
sector_t blocks[MAX_BUF_PER_PAGE];
unsigned page_block; //Increments to 1
unsigned first_hole = blocks_per_page;
struct block_device *bdev = NULL;
int fully_mapped = 1;
unsigned nblocks;
unsigned relative_block;
int err;
/* blkbits = 12 | MAX_BUF_PER_PAGE = 8 */
if (page_has_buffers(page))
goto confused;
/* block_in_file : page->index
* last_block : last page->index of requested nr_pages
* last_block_in_file : always index of last_page_of_file
*/
block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
last_block = block_in_file + nr_pages * blocks_per_page;
last_block_in_file = (i_size_read(inode) + blocksize - 1) >> blkbits;
if (last_block > last_block_in_file)
last_block = last_block_in_file;
page_block = 0;
/*
* Map blocks using the result from the previous get_blocks call first.
*/
/* nblocks : Initially 0 | Later mapped to 1 extent so is mostly 16 */
nblocks = map_bh->b_size >> blkbits;
printk(KERN_INFO "\ncurrent_page : %Lu | nblocks_initial : %u", block_in_file, nblocks);
if (buffer_mapped(map_bh) && block_in_file > *first_logical_block &&
block_in_file < (*first_logical_block + nblocks)) {
unsigned map_offset = block_in_file - *first_logical_block;
unsigned last = nblocks - map_offset;
for (relative_block = 0; ; relative_block++) {
if (relative_block == last) {
clear_buffer_mapped(map_bh);
break;
}
if (page_block == blocks_per_page)
break;
blocks[page_block] = map_bh->b_blocknr + map_offset +
relative_block;
page_block++;
block_in_file++;
}
bdev = map_bh->b_bdev;
}
/*
* Then do more get_blocks calls until we are done with this page.
*/
map_bh->b_page = page;
while (page_block < blocks_per_page) {
map_bh->b_state = 0;
map_bh->b_size = 0;
if (block_in_file < last_block) {
map_bh->b_size = (last_block - block_in_file) << blkbits;
/* use of get_block => ***needs buffer_head map_bh
* bdev = map_bh->b_dev
* physical = map_bh->b_blocknr
* nblocks = map_bh->b_size (no of logical blocks in extent)
* compress_count = map_bh->b_private
* first_logical_block
*/
if (get_block(inode, block_in_file, map_bh, 0)) //BLOCK_MAPPER
goto confused;
*first_logical_block = block_in_file;
}
/* generally is mapped.. so FALSE */
if (!buffer_mapped(map_bh)) {
fully_mapped = 0;
if (first_hole == blocks_per_page)
first_hole = page_block;
page_block++;
block_in_file++;
continue;
}
/* some filesystems will copy data into the page during
* the get_block call, in which case we don't want to
* read it again. map_buffer_to_page copies the data
* we just collected from get_block into the page's buffers
* so readpage doesn't have to repeat the get_block call
*/
//NEXT 3 => FALSE
if (buffer_uptodate(map_bh)) {
printk("\nIn map_buffer_to_page()");
map_buffer_to_page(page, map_bh, page_block);
goto confused;
}
if (first_hole != blocks_per_page)
goto confused; /* hole -> non-hole */
/* Contiguous blocks? */
if (page_block && blocks[page_block-1] != map_bh->b_blocknr-1)
goto confused;
nblocks = map_bh->b_size >> blkbits;
printk(KERN_INFO "\nnblocks_mapped : %u", nblocks);
//MAIN PART
if (!*cb) {
*cb = kzalloc(sizeof(struct compressed_bio), GFP_NOFS);
if (!*cb) {
/* ERROR */
BUG_ON(1);
err = -ENOMEM;
}
err = compressed_bio_init(*cb, inode, *first_logical_block, *(unsigned *)map_bh->b_private,
nblocks << PAGE_CACHE_SHIFT, 0);//compressed_len = 0
if (err) {
/* ERROR = -ENOMEM */
err = -ENOMEM;
}
kfree((unsigned *)map_bh->b_private);
map_bh->b_private = NULL;
}
for (relative_block = 0; ; relative_block++) {
if (relative_block == nblocks) {
clear_buffer_mapped(map_bh);
break;
} else if (page_block == blocks_per_page)
break;
blocks[page_block] = map_bh->b_blocknr+relative_block;
page_block++;
block_in_file++;
}
bdev = map_bh->b_bdev;
}
if (first_hole != blocks_per_page) {
zero_user_segment(page, first_hole << blkbits, PAGE_CACHE_SIZE);
if (first_hole == 0) {
SetPageUptodate(page);
unlock_page(page);
goto out;
}
} else if (fully_mapped) {
//TRUE...REQ?
SetPageMappedToDisk(page);
}
if (fully_mapped && blocks_per_page == 1 && !PageUptodate(page) &&
cleancache_get_page(page) == 0) {
//FALSE
printk(KERN_INFO "\nSet_Page_Uptodate");
SetPageUptodate(page);
goto confused;
}
/*
* This page will go to BIO. Do we need to send this BIO off first?
*/
/* if (bio && (*last_block_in_bio != blocks[0] - 1)) */
/* bio = mpage_bio_submit(READ, bio); */
/* alloc_new: */
/* if (bio == NULL) { */
/* bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9), */
/* min_t(int, nr_pages, bio_get_nr_vecs(bdev)), */
/* GFP_KERNEL); */
/* if (bio == NULL) */
/* goto confused; */
/* } */
/* length = first_hole << blkbits; */
/* if (bio_add_page(bio, page, length, 0) < length) { */
/* bio = mpage_bio_submit(READ, bio); */
/* goto alloc_new; */
/* } */
/* relative_block = block_in_file - *first_logical_block; */
/* nblocks = map_bh->b_size >> blkbits; */
/* if ((buffer_boundary(map_bh) && relative_block == nblocks) || */
/* (first_hole != blocks_per_page)) */
/* bio = mpage_bio_submit(READ, bio); */
/* else */
/* *last_block_in_bio = blocks[blocks_per_page - 1]; */
out:
return bio;
confused:
printk(KERN_INFO "\nCONFUSED !");
if (bio)
bio = mpage_bio_submit(READ, bio);
if (!PageUptodate(page))
block_read_full_page(page, get_block);
else
unlock_page(page);
goto out;
}