btrfs: fix panic caused by direct IO

btrfs paniced when we write >64KB data by direct IO at one time.

Reproduce steps:
 # mkfs.btrfs /dev/sda5 /dev/sda6
 # mount /dev/sda5 /mnt
 # dd if=/dev/zero of=/mnt/tmpfile bs=100K count=1 oflag=direct

Then btrfs paniced:
mapping failed logical 1103155200 bio len 69632 len 12288
------------[ cut here ]------------
kernel BUG at fs/btrfs/volumes.c:3010!
[SNIP]
Pid: 1992, comm: btrfs-worker-0 Not tainted 2.6.37-rc1 #1 D2399/PRIMERGY
RIP: 0010:[<ffffffffa03d1462>]  [<ffffffffa03d1462>] btrfs_map_bio+0x202/0x210 [btrfs]
[SNIP]
Call Trace:
 [<ffffffffa03ab3eb>] __btrfs_submit_bio_done+0x1b/0x20 [btrfs]
 [<ffffffffa03a35ff>] run_one_async_done+0x9f/0xb0 [btrfs]
 [<ffffffffa03d3d20>] run_ordered_completions+0x80/0xc0 [btrfs]
 [<ffffffffa03d45a4>] worker_loop+0x154/0x5f0 [btrfs]
 [<ffffffffa03d4450>] ? worker_loop+0x0/0x5f0 [btrfs]
 [<ffffffffa03d4450>] ? worker_loop+0x0/0x5f0 [btrfs]
 [<ffffffff81083216>] kthread+0x96/0xa0
 [<ffffffff8100cec4>] kernel_thread_helper+0x4/0x10
 [<ffffffff81083180>] ? kthread+0x0/0xa0
 [<ffffffff8100cec0>] ? kernel_thread_helper+0x0/0x10

We fix this problem by splitting bios when we submit bios.

Reported-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Tested-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 184 insertions, 21 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 8c027aa0020a..a47e4faa8c46 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -5535,13 +5535,21 @@ struct btrfs_dio_private {
         u64 bytes;
         u32 *csums;
         void *private;
+
+        /* number of bios pending for this dio */
+        atomic_t pending_bios;
+
+        /* IO errors */
+        int errors;
+
+        struct bio *orig_bio;
 };
 
 static void btrfs_endio_direct_read(struct bio *bio, int err)
 {
+        struct btrfs_dio_private *dip = bio->bi_private;
         struct bio_vec *bvec_end = bio->bi_io_vec + bio->bi_vcnt - 1;
         struct bio_vec *bvec = bio->bi_io_vec;
-        struct btrfs_dio_private *dip = bio->bi_private;
         struct inode *inode = dip->inode;
         struct btrfs_root *root = BTRFS_I(inode)->root;
         u64 start;
@@ -5684,6 +5692,176 @@ static int __btrfs_submit_bio_start_direct_io(struct inode *inode, int rw,
         return 0;
 }
 
+static void btrfs_end_dio_bio(struct bio *bio, int err)
+{
+        struct btrfs_dio_private *dip = bio->bi_private;
+
+        if (err) {
+                printk(KERN_ERR "btrfs direct IO failed ino %lu rw %lu "
+                      "disk_bytenr %lu len %u err no %d\n",
+                      dip->inode->i_ino, bio->bi_rw, bio->bi_sector,
+                      bio->bi_size, err);
+                dip->errors = 1;
+
+                /*
+                 * before atomic variable goto zero, we must make sure
+                 * dip->errors is perceived to be set.
+                 */
+                smp_mb__before_atomic_dec();
+        }
+
+        /* if there are more bios still pending for this dio, just exit */
+        if (!atomic_dec_and_test(&dip->pending_bios))
+                goto out;
+
+        if (dip->errors)
+                bio_io_error(dip->orig_bio);
+        else {
+                set_bit(BIO_UPTODATE, &dip->orig_bio->bi_flags);
+                bio_endio(dip->orig_bio, 0);
+        }
+out:
+        bio_put(bio);
+}
+
+static struct bio *btrfs_dio_bio_alloc(struct block_device *bdev,
+                                       u64 first_sector, gfp_t gfp_flags)
+{
+        int nr_vecs = bio_get_nr_vecs(bdev);
+        return btrfs_bio_alloc(bdev, first_sector, nr_vecs, gfp_flags);
+}
+
+static inline int __btrfs_submit_dio_bio(struct bio *bio, struct inode *inode,
+                                         int rw, u64 file_offset, int skip_sum,
+                                         u32 *csums)
+{
+        int write = rw & REQ_WRITE;
+        struct btrfs_root *root = BTRFS_I(inode)->root;
+        int ret;
+
+        bio_get(bio);
+        ret = btrfs_bio_wq_end_io(root->fs_info, bio, 0);
+        if (ret)
+                goto err;
+
+        if (write && !skip_sum) {
+                ret = btrfs_wq_submit_bio(root->fs_info,
+                                   inode, rw, bio, 0, 0,
+                                   file_offset,
+                                   __btrfs_submit_bio_start_direct_io,
+                                   __btrfs_submit_bio_done);
+                goto err;
+        } else if (!skip_sum)
+                btrfs_lookup_bio_sums_dio(root, inode, bio,
+                                          file_offset, csums);
+
+        ret = btrfs_map_bio(root, rw, bio, 0, 1);
+err:
+        bio_put(bio);
+        return ret;
+}
+
+static int btrfs_submit_direct_hook(int rw, struct btrfs_dio_private *dip,
+                                    int skip_sum)
+{
+        struct inode *inode = dip->inode;
+        struct btrfs_root *root = BTRFS_I(inode)->root;
+        struct btrfs_mapping_tree *map_tree = &root->fs_info->mapping_tree;
+        struct bio *bio;
+        struct bio *orig_bio = dip->orig_bio;
+        struct bio_vec *bvec = orig_bio->bi_io_vec;
+        u64 start_sector = orig_bio->bi_sector;
+        u64 file_offset = dip->logical_offset;
+        u64 submit_len = 0;
+        u64 map_length;
+        int nr_pages = 0;
+        u32 *csums = dip->csums;
+        int ret = 0;
+
+        bio = btrfs_dio_bio_alloc(orig_bio->bi_bdev, start_sector, GFP_NOFS);
+        if (!bio)
+                return -ENOMEM;
+        bio->bi_private = dip;
+        bio->bi_end_io = btrfs_end_dio_bio;
+        atomic_inc(&dip->pending_bios);
+
+        map_length = orig_bio->bi_size;
+        ret = btrfs_map_block(map_tree, READ, start_sector << 9,
+                              &map_length, NULL, 0);
+        if (ret) {
+                bio_put(bio);
+                return -EIO;
+        }
+
+        while (bvec <= (orig_bio->bi_io_vec + orig_bio->bi_vcnt - 1)) {
+                if (unlikely(map_length < submit_len + bvec->bv_len ||
+                    bio_add_page(bio, bvec->bv_page, bvec->bv_len,
+                                 bvec->bv_offset) < bvec->bv_len)) {
+                        /*
+                         * 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 dip might get freed
+                         * before we're done setting it up
+                         */
+                        atomic_inc(&dip->pending_bios);
+                        ret = __btrfs_submit_dio_bio(bio, inode, rw,
+                                                     file_offset, skip_sum,
+                                                     csums);
+                        if (ret) {
+                                bio_put(bio);
+                                atomic_dec(&dip->pending_bios);
+                                goto out_err;
+                        }
+
+                        if (!skip_sum)
+                                csums = csums + nr_pages;
+                        start_sector += submit_len >> 9;
+                        file_offset += submit_len;
+
+                        submit_len = 0;
+                        nr_pages = 0;
+
+                        bio = btrfs_dio_bio_alloc(orig_bio->bi_bdev,
+                                                  start_sector, GFP_NOFS);
+                        if (!bio)
+                                goto out_err;
+                        bio->bi_private = dip;
+                        bio->bi_end_io = btrfs_end_dio_bio;
+
+                        map_length = orig_bio->bi_size;
+                        ret = btrfs_map_block(map_tree, READ, start_sector << 9,
+                                              &map_length, NULL, 0);
+                        if (ret) {
+                                bio_put(bio);
+                                goto out_err;
+                        }
+                } else {
+                        submit_len += bvec->bv_len;
+                        nr_pages ++;
+                        bvec++;
+                }
+        }
+
+        ret = __btrfs_submit_dio_bio(bio, inode, rw, file_offset, skip_sum,
+                                     csums);
+        if (!ret)
+                return 0;
+
+        bio_put(bio);
+out_err:
+        dip->errors = 1;
+        /*
+         * before atomic variable goto zero, we must
+         * make sure dip->errors is perceived to be set.
+         */
+        smp_mb__before_atomic_dec();
+        if (atomic_dec_and_test(&dip->pending_bios))
+                bio_io_error(dip->orig_bio);
+
+        /* bio_end_io() will handle error, so we needn't return it */
+        return 0;
+}
+
 static void btrfs_submit_direct(int rw, struct bio *bio, struct inode *inode,
                                 loff_t file_offset)
 {
@@ -5723,33 +5901,18 @@ static void btrfs_submit_direct(int rw, struct bio *bio, struct inode *inode,
 
         dip->disk_bytenr = (u64)bio->bi_sector << 9;
         bio->bi_private = dip;
+        dip->errors = 0;
+        dip->orig_bio = bio;
+        atomic_set(&dip->pending_bios, 0);
 
         if (write)
                 bio->bi_end_io = btrfs_endio_direct_write;
         else
                 bio->bi_end_io = btrfs_endio_direct_read;
 
-        ret = btrfs_bio_wq_end_io(root->fs_info, bio, 0);
-        if (ret)
-                goto free_ordered;
-
-        if (write && !skip_sum) {
-                ret = btrfs_wq_submit_bio(BTRFS_I(inode)->root->fs_info,
-                                   inode, rw, bio, 0, 0,
-                                   dip->logical_offset,
-                                   __btrfs_submit_bio_start_direct_io,
-                                   __btrfs_submit_bio_done);
-                if (ret)
-                        goto free_ordered;
+        ret = btrfs_submit_direct_hook(rw, dip, skip_sum);
+        if (!ret)
                 return;
-        } else if (!skip_sum)
-                btrfs_lookup_bio_sums_dio(root, inode, bio,
-                                          dip->logical_offset, dip->csums);
-
-        ret = btrfs_map_bio(root, rw, bio, 0, 1);
-        if (ret)
-                goto free_ordered;
-        return;
 free_ordered:
         /*
          * If this is a write, we need to clean up the reserved space and kill