devpts: remove graffiti

[linux-2.6/mini2440.git] / fs / btrfs / compression.c

/*
 * Copyright (C) 2008 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/kernel.h>
#include <linux/bio.h>
#include <linux/buffer_head.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/time.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/smp_lock.h>
#include <linux/backing-dev.h>
#include <linux/mpage.h>
#include <linux/swap.h>
#include <linux/writeback.h>
#include <linux/bit_spinlock.h>
#include <linux/pagevec.h>
#include "compat.h"
#include "ctree.h"
#include "disk-io.h"
#include "transaction.h"
#include "btrfs_inode.h"
#include "volumes.h"
#include "ordered-data.h"
#include "compression.h"
#include "extent_io.h"
#include "extent_map.h"

struct compressed_bio {
        /* number of bios pending for this compressed extent */
        atomic_t pending_bios;

        /* the pages with the compressed data on them */
        struct page **compressed_pages;

        /* inode that owns this data */
        struct inode *inode;

        /* starting offset in the inode for our pages */
        u64 start;

        /* number of bytes in the inode we're working on */
        unsigned long len;

        /* number of bytes on disk */
        unsigned long compressed_len;

        /* number of compressed pages in the array */
        unsigned long nr_pages;

        /* IO errors */
        int errors;
        int mirror_num;

        /* for reads, this is the bio we are copying the data into */
        struct bio *orig_bio;

        /*
         * the start of a variable length array of checksums only
         * used by reads
         */
        u32 sums;
};

static inline int compressed_bio_size(struct btrfs_root *root,
                                      unsigned long disk_size)
{
        u16 csum_size = btrfs_super_csum_size(&root->fs_info->super_copy);
        return sizeof(struct compressed_bio) +
                ((disk_size + root->sectorsize - 1) / root->sectorsize) *
                csum_size;
}

static struct bio *compressed_bio_alloc(struct block_device *bdev,
                                        u64 first_byte, gfp_t gfp_flags)
{
        struct bio *bio;
        int nr_vecs;

        nr_vecs = bio_get_nr_vecs(bdev);
        bio = bio_alloc(gfp_flags, nr_vecs);

        if (bio == NULL && (current->flags & PF_MEMALLOC)) {
                while (!bio && (nr_vecs /= 2))
                        bio = bio_alloc(gfp_flags, nr_vecs);
        }

        if (bio) {
                bio->bi_size = 0;
                bio->bi_bdev = bdev;
                bio->bi_sector = first_byte >> 9;
        }
        return bio;
}

static int check_compressed_csum(struct inode *inode,
                                 struct compressed_bio *cb,
                                 u64 disk_start)
{
        int ret;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct page *page;
        unsigned long i;
        char *kaddr;
        u32 csum;
        u32 *cb_sum = &cb->sums;

        if (btrfs_test_flag(inode, NODATASUM))
                return 0;

        for (i = 0; i < cb->nr_pages; i++) {
                page = cb->compressed_pages[i];
                csum = ~(u32)0;

                kaddr = kmap_atomic(page, KM_USER0);
                csum = btrfs_csum_data(root, kaddr, csum, PAGE_CACHE_SIZE);
                btrfs_csum_final(csum, (char *)&csum);
                kunmap_atomic(kaddr, KM_USER0);

                if (csum != *cb_sum) {
                        printk(KERN_INFO "btrfs csum failed ino %lu "
                               "extent %llu csum %u "
                               "wanted %u mirror %d\n", inode->i_ino,
                               (unsigned long long)disk_start,
                               csum, *cb_sum, cb->mirror_num);
                        ret = -EIO;
                        goto fail;
                }
                cb_sum++;

        }
        ret = 0;
fail:
        return ret;
}

/* when we finish reading compressed pages from the disk, we
 * decompress them and then run the bio end_io routines on the
 * decompressed pages (in the inode address space).
 *
 * This allows the checksumming and other IO error handling routines
 * to work normally
 *
 * The compressed pages are freed here, and it must be run
 * in process context
 */
static void end_compressed_bio_read(struct bio *bio, int err)
{
        struct extent_io_tree *tree;
        struct compressed_bio *cb = bio->bi_private;
        struct inode *inode;
        struct page *page;
        unsigned long index;
        int ret;

        if (err)
                cb->errors = 1;

        /* if there are more bios still pending for this compressed
         * extent, just exit
         */
        if (!atomic_dec_and_test(&cb->pending_bios))
                goto out;

        inode = cb->inode;
        ret = check_compressed_csum(inode, cb, (u64)bio->bi_sector << 9);
        if (ret)
                goto csum_failed;

        /* ok, we're the last bio for this extent, lets start
         * the decompression.
         */
        tree = &BTRFS_I(inode)->io_tree;
        ret = btrfs_zlib_decompress_biovec(cb->compressed_pages,
                                        cb->start,
                                        cb->orig_bio->bi_io_vec,
                                        cb->orig_bio->bi_vcnt,
                                        cb->compressed_len);
csum_failed:
        if (ret)
                cb->errors = 1;

        /* release the compressed pages */
        index = 0;
        for (index = 0; index < cb->nr_pages; index++) {
                page = cb->compressed_pages[index];
                page->mapping = NULL;
                page_cache_release(page);
        }

        /* do io completion on the original bio */
        if (cb->errors) {
                bio_io_error(cb->orig_bio);
        } else {
                int bio_index = 0;
                struct bio_vec *bvec = cb->orig_bio->bi_io_vec;

                /*
                 * we have verified the checksum already, set page
                 * checked so the end_io handlers know about it
                 */
                while (bio_index < cb->orig_bio->bi_vcnt) {
                        SetPageChecked(bvec->bv_page);
                        bvec++;
                        bio_index++;
                }
                bio_endio(cb->orig_bio, 0);
        }

        /* finally free the cb struct */
        kfree(cb->compressed_pages);
        kfree(cb);
out:
        bio_put(bio);
}

/*
 * Clear the writeback bits on all of the file
 * pages for a compressed write
 */
static noinline int end_compressed_writeback(struct inode *inode, u64 start,
                                             unsigned long ram_size)
{
        unsigned long index = start >> PAGE_CACHE_SHIFT;
        unsigned long end_index = (start + ram_size - 1) >> PAGE_CACHE_SHIFT;
        struct page *pages[16];
        unsigned long nr_pages = end_index - index + 1;
        int i;
        int ret;

        while (nr_pages > 0) {
                ret = find_get_pages_contig(inode->i_mapping, index,
                                     min_t(unsigned long,
                                     nr_pages, ARRAY_SIZE(pages)), pages);
                if (ret == 0) {
                        nr_pages -= 1;
                        index += 1;
                        continue;
                }
                for (i = 0; i < ret; i++) {
                        end_page_writeback(pages[i]);
                        page_cache_release(pages[i]);
                }
                nr_pages -= ret;
                index += ret;
        }
        /* the inode may be gone now */
        return 0;
}

/*
 * do the cleanup once all the compressed pages hit the disk.
 * This will clear writeback on the file pages and free the compressed
 * pages.
 *
 * This also calls the writeback end hooks for the file pages so that
 * metadata and checksums can be updated in the file.
 */
static void end_compressed_bio_write(struct bio *bio, int err)
{
        struct extent_io_tree *tree;
        struct compressed_bio *cb = bio->bi_private;
        struct inode *inode;
        struct page *page;
        unsigned long index;

        if (err)
                cb->errors = 1;

        /* if there are more bios still pending for this compressed
         * extent, just exit
         */
        if (!atomic_dec_and_test(&cb->pending_bios))
                goto out;

        /* ok, we're the last bio for this extent, step one is to
         * call back into the FS and do all the end_io operations
         */
        inode = cb->inode;
        tree = &BTRFS_I(inode)->io_tree;
        cb->compressed_pages[0]->mapping = cb->inode->i_mapping;
        tree->ops->writepage_end_io_hook(cb->compressed_pages[0],
                                         cb->start,
                                         cb->start + cb->len - 1,
                                         NULL, 1);
        cb->compressed_pages[0]->mapping = NULL;

        end_compressed_writeback(inode, cb->start, cb->len);
        /* note, our inode could be gone now */

        /*
         * release the compressed pages, these came from alloc_page and
         * are not attached to the inode at all
         */
        index = 0;
        for (index = 0; index < cb->nr_pages; index++) {
                page = cb->compressed_pages[index];
                page->mapping = NULL;
                page_cache_release(page);
        }

        /* finally free the cb struct */
        kfree(cb->compressed_pages);
        kfree(cb);
out:
        bio_put(bio);
}

/*
 * worker function to build and submit bios for previously compressed pages.
 * The corresponding pages in the inode should be marked for writeback
 * and the compressed pages should have a reference on them for dropping
 * when the IO is complete.
 *
 * This also checksums the file bytes and gets things ready for
 * the end io hooks.
 */
int btrfs_submit_compressed_write(struct inode *inode, u64 start,
                                 unsigned long len, u64 disk_start,
                                 unsigned long compressed_len,
                                 struct page **compressed_pages,
                                 unsigned long nr_pages)
{
        struct bio *bio = NULL;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct compressed_bio *cb;
        unsigned long bytes_left;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        int page_index = 0;
        struct page *page;
        u64 first_byte = disk_start;
        struct block_device *bdev;
        int ret;

        WARN_ON(start & ((u64)PAGE_CACHE_SIZE - 1));
        cb = kmalloc(compressed_bio_size(root, compressed_len), GFP_NOFS);
        atomic_set(&cb->pending_bios, 0);
        cb->errors = 0;
        cb->inode = inode;
        cb->start = start;
        cb->len = len;
        cb->mirror_num = 0;
        cb->compressed_pages = compressed_pages;
        cb->compressed_len = compressed_len;
        cb->orig_bio = NULL;
        cb->nr_pages = nr_pages;

        bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;

        bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
        bio->bi_private = cb;
        bio->bi_end_io = end_compressed_bio_write;
        atomic_inc(&cb->pending_bios);

        /* create and submit bios for the compressed pages */
        bytes_left = compressed_len;
        for (page_index = 0; page_index < cb->nr_pages; page_index++) {
                page = compressed_pages[page_index];
                page->mapping = inode->i_mapping;
                if (bio->bi_size)
                        ret = io_tree->ops->merge_bio_hook(page, 0,
                                                           PAGE_CACHE_SIZE,
                                                           bio, 0);
                else
                        ret = 0;

                page->mapping = NULL;
                if (ret || bio_add_page(bio, page, PAGE_CACHE_SIZE, 0) <
                    PAGE_CACHE_SIZE) {
                        bio_get(bio);

                        /*
                         * inc the count before we submit the bio so
                         * we know the end IO handler won't happen before
                         * we inc the count.  Otherwise, the cb might get
                         * freed before we're done setting it up
                         */
                        atomic_inc(&cb->pending_bios);
                        ret = btrfs_bio_wq_end_io(root->fs_info, bio, 0);
                        BUG_ON(ret);

                        ret = btrfs_csum_one_bio(root, inode, bio, start, 1);
                        BUG_ON(ret);

                        ret = btrfs_map_bio(root, WRITE, bio, 0, 1);
                        BUG_ON(ret);

                        bio_put(bio);

                        bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
                        bio->bi_private = cb;
                        bio->bi_end_io = end_compressed_bio_write;
                        bio_add_page(bio, page, PAGE_CACHE_SIZE, 0);
                }
                if (bytes_left < PAGE_CACHE_SIZE) {
                        printk("bytes left %lu compress len %lu nr %lu\n",
                               bytes_left, cb->compressed_len, cb->nr_pages);
                }
                bytes_left -= PAGE_CACHE_SIZE;
                first_byte += PAGE_CACHE_SIZE;
                cond_resched();
        }
        bio_get(bio);

        ret = btrfs_bio_wq_end_io(root->fs_info, bio, 0);
        BUG_ON(ret);

        ret = btrfs_csum_one_bio(root, inode, bio, start, 1);
        BUG_ON(ret);

        ret = btrfs_map_bio(root, WRITE, bio, 0, 1);
        BUG_ON(ret);

        bio_put(bio);
        return 0;
}

static noinline int add_ra_bio_pages(struct inode *inode,
                                     u64 compressed_end,
                                     struct compressed_bio *cb)
{
        unsigned long end_index;
        unsigned long page_index;
        u64 last_offset;
        u64 isize = i_size_read(inode);
        int ret;
        struct page *page;
        unsigned long nr_pages = 0;
        struct extent_map *em;
        struct address_space *mapping = inode->i_mapping;
        struct pagevec pvec;
        struct extent_map_tree *em_tree;
        struct extent_io_tree *tree;
        u64 end;
        int misses = 0;

        page = cb->orig_bio->bi_io_vec[cb->orig_bio->bi_vcnt - 1].bv_page;
        last_offset = (page_offset(page) + PAGE_CACHE_SIZE);
        em_tree = &BTRFS_I(inode)->extent_tree;
        tree = &BTRFS_I(inode)->io_tree;

        if (isize == 0)
                return 0;

        end_index = (i_size_read(inode) - 1) >> PAGE_CACHE_SHIFT;

        pagevec_init(&pvec, 0);
        while (last_offset < compressed_end) {
                page_index = last_offset >> PAGE_CACHE_SHIFT;

                if (page_index > end_index)
                        break;

                rcu_read_lock();
                page = radix_tree_lookup(&mapping->page_tree, page_index);
                rcu_read_unlock();
                if (page) {
                        misses++;
                        if (misses > 4)
                                break;
                        goto next;
                }

                page = alloc_page(mapping_gfp_mask(mapping) | GFP_NOFS);
                if (!page)
                        break;

                page->index = page_index;
                /*
                 * what we want to do here is call add_to_page_cache_lru,
                 * but that isn't exported, so we reproduce it here
                 */
                if (add_to_page_cache(page, mapping,
                                      page->index, GFP_NOFS)) {
                        page_cache_release(page);
                        goto next;
                }

                /* open coding of lru_cache_add, also not exported */
                page_cache_get(page);
                if (!pagevec_add(&pvec, page))
                        __pagevec_lru_add_file(&pvec);

                end = last_offset + PAGE_CACHE_SIZE - 1;
                /*
                 * at this point, we have a locked page in the page cache
                 * for these bytes in the file.  But, we have to make
                 * sure they map to this compressed extent on disk.
                 */
                set_page_extent_mapped(page);
                lock_extent(tree, last_offset, end, GFP_NOFS);
                spin_lock(&em_tree->lock);
                em = lookup_extent_mapping(em_tree, last_offset,
                                           PAGE_CACHE_SIZE);
                spin_unlock(&em_tree->lock);

                if (!em || last_offset < em->start ||
                    (last_offset + PAGE_CACHE_SIZE > extent_map_end(em)) ||
                    (em->block_start >> 9) != cb->orig_bio->bi_sector) {
                        free_extent_map(em);
                        unlock_extent(tree, last_offset, end, GFP_NOFS);
                        unlock_page(page);
                        page_cache_release(page);
                        break;
                }
                free_extent_map(em);

                if (page->index == end_index) {
                        char *userpage;
                        size_t zero_offset = isize & (PAGE_CACHE_SIZE - 1);

                        if (zero_offset) {
                                int zeros;
                                zeros = PAGE_CACHE_SIZE - zero_offset;
                                userpage = kmap_atomic(page, KM_USER0);
                                memset(userpage + zero_offset, 0, zeros);
                                flush_dcache_page(page);
                                kunmap_atomic(userpage, KM_USER0);
                        }
                }

                ret = bio_add_page(cb->orig_bio, page,
                                   PAGE_CACHE_SIZE, 0);

                if (ret == PAGE_CACHE_SIZE) {
                        nr_pages++;
                        page_cache_release(page);
                } else {
                        unlock_extent(tree, last_offset, end, GFP_NOFS);
                        unlock_page(page);
                        page_cache_release(page);
                        break;
                }
next:
                last_offset += PAGE_CACHE_SIZE;
        }
        if (pagevec_count(&pvec))
                __pagevec_lru_add_file(&pvec);
        return 0;
}

/*
 * for a compressed read, the bio we get passed has all the inode pages
 * in it.  We don't actually do IO on those pages but allocate new ones
 * to hold the compressed pages on disk.
 *
 * bio->bi_sector points to the compressed extent on disk
 * bio->bi_io_vec points to all of the inode pages
 * bio->bi_vcnt is a count of pages
 *
 * After the compressed pages are read, we copy the bytes into the
 * bio we were passed and then call the bio end_io calls
 */
int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
                                 int mirror_num, unsigned long bio_flags)
{
        struct extent_io_tree *tree;
        struct extent_map_tree *em_tree;
        struct compressed_bio *cb;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        unsigned long uncompressed_len = bio->bi_vcnt * PAGE_CACHE_SIZE;
        unsigned long compressed_len;
        unsigned long nr_pages;
        unsigned long page_index;
        struct page *page;
        struct block_device *bdev;
        struct bio *comp_bio;
        u64 cur_disk_byte = (u64)bio->bi_sector << 9;
        u64 em_len;
        u64 em_start;
        struct extent_map *em;
        int ret;
        u32 *sums;

        tree = &BTRFS_I(inode)->io_tree;
        em_tree = &BTRFS_I(inode)->extent_tree;

        /* we need the actual starting offset of this extent in the file */
        spin_lock(&em_tree->lock);
        em = lookup_extent_mapping(em_tree,
                                   page_offset(bio->bi_io_vec->bv_page),
                                   PAGE_CACHE_SIZE);
        spin_unlock(&em_tree->lock);

        compressed_len = em->block_len;
        cb = kmalloc(compressed_bio_size(root, compressed_len), GFP_NOFS);
        atomic_set(&cb->pending_bios, 0);
        cb->errors = 0;
        cb->inode = inode;
        cb->mirror_num = mirror_num;
        sums = &cb->sums;

        cb->start = em->orig_start;
        em_len = em->len;
        em_start = em->start;

        free_extent_map(em);
        em = NULL;

        cb->len = uncompressed_len;
        cb->compressed_len = compressed_len;
        cb->orig_bio = bio;

        nr_pages = (compressed_len + PAGE_CACHE_SIZE - 1) /
                                 PAGE_CACHE_SIZE;
        cb->compressed_pages = kmalloc(sizeof(struct page *) * nr_pages,
                                       GFP_NOFS);
        bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;

        for (page_index = 0; page_index < nr_pages; page_index++) {
                cb->compressed_pages[page_index] = alloc_page(GFP_NOFS |
                                                              __GFP_HIGHMEM);
        }
        cb->nr_pages = nr_pages;

        add_ra_bio_pages(inode, em_start + em_len, cb);

        /* include any pages we added in add_ra-bio_pages */
        uncompressed_len = bio->bi_vcnt * PAGE_CACHE_SIZE;
        cb->len = uncompressed_len;

        comp_bio = compressed_bio_alloc(bdev, cur_disk_byte, GFP_NOFS);
        comp_bio->bi_private = cb;
        comp_bio->bi_end_io = end_compressed_bio_read;
        atomic_inc(&cb->pending_bios);

        for (page_index = 0; page_index < nr_pages; page_index++) {
                page = cb->compressed_pages[page_index];
                page->mapping = inode->i_mapping;
                page->index = em_start >> PAGE_CACHE_SHIFT;

                if (comp_bio->bi_size)
                        ret = tree->ops->merge_bio_hook(page, 0,
                                                        PAGE_CACHE_SIZE,
                                                        comp_bio, 0);
                else
                        ret = 0;

                page->mapping = NULL;
                if (ret || bio_add_page(comp_bio, page, PAGE_CACHE_SIZE, 0) <
                    PAGE_CACHE_SIZE) {
                        bio_get(comp_bio);

                        ret = btrfs_bio_wq_end_io(root->fs_info, comp_bio, 0);
                        BUG_ON(ret);

                        /*
                         * inc the count before we submit the bio so
                         * we know the end IO handler won't happen before
                         * we inc the count.  Otherwise, the cb might get
                         * freed before we're done setting it up
                         */
                        atomic_inc(&cb->pending_bios);

                        if (!btrfs_test_flag(inode, NODATASUM)) {
                                btrfs_lookup_bio_sums(root, inode, comp_bio,
                                                      sums);
                        }
                        sums += (comp_bio->bi_size + root->sectorsize - 1) /
                                root->sectorsize;

                        ret = btrfs_map_bio(root, READ, comp_bio,
                                            mirror_num, 0);
                        BUG_ON(ret);

                        bio_put(comp_bio);

                        comp_bio = compressed_bio_alloc(bdev, cur_disk_byte,
                                                        GFP_NOFS);
                        comp_bio->bi_private = cb;
                        comp_bio->bi_end_io = end_compressed_bio_read;

                        bio_add_page(comp_bio, page, PAGE_CACHE_SIZE, 0);
                }
                cur_disk_byte += PAGE_CACHE_SIZE;
        }
        bio_get(comp_bio);

        ret = btrfs_bio_wq_end_io(root->fs_info, comp_bio, 0);
        BUG_ON(ret);

        if (!btrfs_test_flag(inode, NODATASUM))
                btrfs_lookup_bio_sums(root, inode, comp_bio, sums);

        ret = btrfs_map_bio(root, READ, comp_bio, mirror_num, 0);
        BUG_ON(ret);

        bio_put(comp_bio);
        return 0;
}