Btrfs: Do metadata checksums for reads via a workqueue
Before, metadata checksumming was done by the callers of read_tree_block,
which would set EXTENT_CSUM bits in the extent tree to show that a given
range of pages was already checksummed and didn't need to be verified
again.
But, those bits could go away via try_to_releasepage, and the end
result was bogus checksum failures on pages that never left the cache.
The new code validates checksums when the page is read. It is a little
tricky because metadata blocks can span pages and a single read may
end up going via multiple bios.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index e444b99..8210920 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -24,6 +24,7 @@
#include <linux/radix-tree.h>
#include <linux/writeback.h>
#include <linux/buffer_head.h> // for block_sync_page
+#include <linux/workqueue.h>
#include "ctree.h"
#include "disk-io.h"
#include "transaction.h"
@@ -45,6 +46,16 @@
#endif
static struct extent_io_ops btree_extent_io_ops;
+static struct workqueue_struct *end_io_workqueue;
+
+struct end_io_wq {
+ struct bio *bio;
+ bio_end_io_t *end_io;
+ void *private;
+ struct btrfs_fs_info *info;
+ int error;
+ struct list_head list;
+};
struct extent_map *btree_get_extent(struct inode *inode, struct page *page,
size_t page_offset, u64 start, u64 len,
@@ -219,11 +230,108 @@
return 0;
}
+int btree_readpage_end_io_hook(struct page *page, u64 start, u64 end,
+ struct extent_state *state)
+{
+ struct extent_io_tree *tree;
+ u64 found_start;
+ int found_level;
+ unsigned long len;
+ struct extent_buffer *eb;
+ struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;
+ int ret;
+
+ tree = &BTRFS_I(page->mapping->host)->io_tree;
+ if (page->private == EXTENT_PAGE_PRIVATE)
+ goto out;
+ if (!page->private)
+ goto out;
+ len = page->private >> 2;
+ if (len == 0) {
+ WARN_ON(1);
+ }
+ eb = alloc_extent_buffer(tree, start, len, page, GFP_NOFS);
+ read_extent_buffer_pages(tree, eb, start + PAGE_CACHE_SIZE, 1,
+ btree_get_extent);
+ btrfs_clear_buffer_defrag(eb);
+ found_start = btrfs_header_bytenr(eb);
+ if (found_start != start) {
+ printk("warning: eb start incorrect %Lu buffer %Lu len %lu\n",
+ start, found_start, len);
+ WARN_ON(1);
+ goto err;
+ }
+ if (eb->first_page != page) {
+ printk("bad first page %lu %lu\n", eb->first_page->index,
+ page->index);
+ WARN_ON(1);
+ goto err;
+ }
+ found_level = btrfs_header_level(eb);
+
+ ret = csum_tree_block(root, eb, 1);
+
+ end = min_t(u64, eb->len, PAGE_CACHE_SIZE);
+ end = eb->start + end - 1;
+ release_extent_buffer_tail_pages(eb);
+err:
+ free_extent_buffer(eb);
+out:
+ return 0;
+}
+
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,23)
+static void end_workqueue_bio(struct bio *bio, int err)
+#else
+static int end_workqueue_bio(struct bio *bio,
+ unsigned int bytes_done, int err)
+#endif
+{
+ struct end_io_wq *end_io_wq = bio->bi_private;
+ struct btrfs_fs_info *fs_info;
+ unsigned long flags;
+
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,23)
+ if (bio->bi_size)
+ return 1;
+#endif
+
+ fs_info = end_io_wq->info;
+ spin_lock_irqsave(&fs_info->end_io_work_lock, flags);
+ end_io_wq->error = err;
+ list_add_tail(&end_io_wq->list, &fs_info->end_io_work_list);
+ spin_unlock_irqrestore(&fs_info->end_io_work_lock, flags);
+ queue_work(end_io_workqueue, &fs_info->end_io_work);
+
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,23)
+ return 0;
+#endif
+}
+
static int btree_submit_bio_hook(struct inode *inode, int rw, struct bio *bio)
{
struct btrfs_root *root = BTRFS_I(inode)->root;
+ struct end_io_wq *end_io_wq;
u64 offset;
offset = bio->bi_sector << 9;
+
+ if (rw & (1 << BIO_RW)) {
+ return btrfs_map_bio(BTRFS_I(inode)->root, rw, bio);
+ }
+
+ end_io_wq = kmalloc(sizeof(*end_io_wq), GFP_NOFS);
+ if (!end_io_wq)
+ return -ENOMEM;
+
+ end_io_wq->private = bio->bi_private;
+ end_io_wq->end_io = bio->bi_end_io;
+ end_io_wq->info = root->fs_info;
+ end_io_wq->error = 0;
+ end_io_wq->bio = bio;
+
+ bio->bi_private = end_io_wq;
+ bio->bi_end_io = end_workqueue_bio;
+
if (offset == BTRFS_SUPER_INFO_OFFSET) {
bio->bi_bdev = root->fs_info->sb->s_bdev;
submit_bio(rw, bio);
@@ -363,36 +471,7 @@
int btrfs_verify_block_csum(struct btrfs_root *root,
struct extent_buffer *buf)
{
- struct extent_io_tree *io_tree;
- u64 end;
- int ret;
-
- io_tree = &BTRFS_I(root->fs_info->btree_inode)->io_tree;
- if (buf->flags & EXTENT_CSUM)
- return 0;
-
- end = min_t(u64, buf->len, PAGE_CACHE_SIZE);
- end = buf->start + end - 1;
- if (test_range_bit(io_tree, buf->start, end, EXTENT_CSUM, 1)) {
- buf->flags |= EXTENT_CSUM;
- return 0;
- }
- lock_extent(io_tree, buf->start, end, GFP_NOFS);
-
- if (test_range_bit(io_tree, buf->start, end, EXTENT_CSUM, 1)) {
- buf->flags |= EXTENT_CSUM;
- ret = 0;
- goto out_unlock;
- }
-WARN_ON(buf->flags & EXTENT_CSUM);
-
- ret = csum_tree_block(root, buf, 1);
- set_extent_bits(io_tree, buf->start, end, EXTENT_CSUM, GFP_NOFS);
- buf->flags |= EXTENT_CSUM;
-
-out_unlock:
- unlock_extent(io_tree, buf->start, end, GFP_NOFS);
- return ret;
+ return btrfs_buffer_uptodate(buf);
}
struct extent_buffer *btrfs_find_tree_block(struct btrfs_root *root,
@@ -430,11 +509,15 @@
buf = btrfs_find_create_tree_block(root, bytenr, blocksize);
if (!buf)
return NULL;
- read_extent_buffer_pages(&BTRFS_I(btree_inode)->io_tree, buf, 0, 1,
- btree_get_extent);
- ret = btrfs_verify_block_csum(root, buf);
+ ret = read_extent_buffer_pages(&BTRFS_I(btree_inode)->io_tree, buf, 0,
+ 1, btree_get_extent);
+
+ if (ret == 0) {
+ buf->flags |= EXTENT_UPTODATE;
+ }
return buf;
+
}
int clean_tree_block(struct btrfs_trans_handle *trans, struct btrfs_root *root,
@@ -724,6 +807,99 @@
return 0;
}
+static int bio_ready_for_csum(struct bio *bio)
+{
+ u64 length = 0;
+ u64 buf_len = 0;
+ u64 start = 0;
+ struct page *page;
+ struct extent_io_tree *io_tree = NULL;
+ struct btrfs_fs_info *info = NULL;
+ struct bio_vec *bvec;
+ int i;
+ int ret;
+
+ bio_for_each_segment(bvec, bio, i) {
+ page = bvec->bv_page;
+ if (page->private == EXTENT_PAGE_PRIVATE) {
+ length += bvec->bv_len;
+ continue;
+ }
+ if (!page->private) {
+ length += bvec->bv_len;
+ continue;
+ }
+ length = bvec->bv_len;
+ buf_len = page->private >> 2;
+ start = page_offset(page) + bvec->bv_offset;
+ io_tree = &BTRFS_I(page->mapping->host)->io_tree;
+ info = BTRFS_I(page->mapping->host)->root->fs_info;
+ }
+ /* are we fully contained in this bio? */
+ if (buf_len <= length)
+ return 1;
+
+ ret = extent_range_uptodate(io_tree, start + length,
+ start + buf_len - 1);
+ if (ret == 1)
+ return ret;
+ return ret;
+}
+
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,18)
+void btrfs_end_io_csum(void *p)
+#else
+void btrfs_end_io_csum(struct work_struct *work)
+#endif
+{
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,18)
+ struct btrfs_fs_info *fs_info = p;
+#else
+ struct btrfs_fs_info *fs_info = container_of(work,
+ struct btrfs_fs_info,
+ end_io_work);
+#endif
+ unsigned long flags;
+ struct end_io_wq *end_io_wq;
+ struct bio *bio;
+ struct list_head *next;
+ int error;
+ int was_empty;
+
+ while(1) {
+ spin_lock_irqsave(&fs_info->end_io_work_lock, flags);
+ if (list_empty(&fs_info->end_io_work_list)) {
+ spin_unlock_irqrestore(&fs_info->end_io_work_lock,
+ flags);
+ return;
+ }
+ next = fs_info->end_io_work_list.next;
+ list_del(next);
+ spin_unlock_irqrestore(&fs_info->end_io_work_lock, flags);
+
+ end_io_wq = list_entry(next, struct end_io_wq, list);
+
+ bio = end_io_wq->bio;
+ if (!bio_ready_for_csum(bio)) {
+ spin_lock_irqsave(&fs_info->end_io_work_lock, flags);
+ was_empty = list_empty(&fs_info->end_io_work_list);
+ list_add_tail(&end_io_wq->list,
+ &fs_info->end_io_work_list);
+ spin_unlock_irqrestore(&fs_info->end_io_work_lock,
+ flags);
+ if (was_empty)
+ return;
+ continue;
+ }
+ error = end_io_wq->error;
+ bio->bi_private = end_io_wq->private;
+ bio->bi_end_io = end_io_wq->end_io;
+ kfree(end_io_wq);
+ bio_endio(bio, error);
+ }
+}
+
+
struct btrfs_root *open_ctree(struct super_block *sb,
struct btrfs_fs_devices *fs_devices)
{
@@ -750,11 +926,16 @@
err = -ENOMEM;
goto fail;
}
+ end_io_workqueue = create_workqueue("btrfs-end-io");
+ BUG_ON(!end_io_workqueue);
+
INIT_RADIX_TREE(&fs_info->fs_roots_radix, GFP_NOFS);
INIT_LIST_HEAD(&fs_info->trans_list);
INIT_LIST_HEAD(&fs_info->dead_roots);
INIT_LIST_HEAD(&fs_info->hashers);
+ INIT_LIST_HEAD(&fs_info->end_io_work_list);
spin_lock_init(&fs_info->hash_lock);
+ spin_lock_init(&fs_info->end_io_work_lock);
spin_lock_init(&fs_info->delalloc_lock);
spin_lock_init(&fs_info->new_trans_lock);
@@ -799,6 +980,7 @@
fs_info->btree_inode->i_mapping, GFP_NOFS);
fs_info->do_barriers = 1;
+ INIT_WORK(&fs_info->end_io_work, btrfs_end_io_csum);
#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,18)
INIT_WORK(&fs_info->trans_work, btrfs_transaction_cleaner, fs_info);
#else
@@ -1044,6 +1226,8 @@
extent_io_tree_empty_lru(&BTRFS_I(fs_info->btree_inode)->io_tree);
truncate_inode_pages(fs_info->btree_inode->i_mapping, 0);
+ flush_workqueue(end_io_workqueue);
+ destroy_workqueue(end_io_workqueue);
iput(fs_info->btree_inode);
#if 0
@@ -1171,12 +1355,18 @@
{
struct btrfs_root *root = BTRFS_I(buf->first_page->mapping->host)->root;
struct inode *btree_inode = root->fs_info->btree_inode;
- return read_extent_buffer_pages(&BTRFS_I(btree_inode)->io_tree,
+ int ret;
+ ret = read_extent_buffer_pages(&BTRFS_I(btree_inode)->io_tree,
buf, 0, 1, btree_get_extent);
+ if (ret == 0) {
+ buf->flags |= EXTENT_UPTODATE;
+ }
+ return ret;
}
static struct extent_io_ops btree_extent_io_ops = {
.writepage_io_hook = btree_writepage_io_hook,
+ .readpage_end_io_hook = btree_readpage_end_io_hook,
.submit_bio_hook = btree_submit_bio_hook,
/* note we're sharing with inode.c for the merge bio hook */
.merge_bio_hook = btrfs_merge_bio_hook,