On Tue, Jul 29, 2014 at 10:24 AM, Miao Xie <miaox@xxxxxxxxxxxxxx> wrote:
> The current code would load checksum data for several times when we split
> a whole direct read io because of the limit of the raid stripe, it would
> make us search the csum tree for several times. In fact, it just wasted time,
> and made the contention of the csum tree root be more serious. This patch
> improves this problem by loading the data at once.
>
> Signed-off-by: Miao Xie <miaox@xxxxxxxxxxxxxx>
> ---
> Changelog v1 -> v2:
> - Remove the __GFP_ZERO flag in btrfs_submit_direct because it would trigger
> a WARNing. It is reported by Filipe David Manana, Thanks.
Hi Miao,
Without this flag (to zero the struct), I get a general protection fault at:
(gdb) list *(btrfs_endio_direct_read+0xb8)
0x38378 is in btrfs_endio_direct_read (fs/btrfs/inode.c:7242).
7237 if (err)
7238 clear_bit(BIO_UPTODATE, &dio_bio->bi_flags);
7239 dio_end_io(dio_bio, err);
7240
7241 if (io_bio->end_io)
7242 io_bio->end_io(io_bio, err);
7243 bio_put(bio);
7244 }
Happens when running xfstests/generic/091
> ---
> fs/btrfs/btrfs_inode.h | 1 -
> fs/btrfs/ctree.h | 3 +--
> fs/btrfs/extent_io.c | 13 +++++++++++--
> fs/btrfs/file-item.c | 14 ++------------
> fs/btrfs/inode.c | 38 +++++++++++++++++++++-----------------
> 5 files changed, 35 insertions(+), 34 deletions(-)
>
> diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
> index a0cf3e5..b69bf7e 100644
> --- a/fs/btrfs/btrfs_inode.h
> +++ b/fs/btrfs/btrfs_inode.h
> @@ -263,7 +263,6 @@ struct btrfs_dio_private {
>
> /* dio_bio came from fs/direct-io.c */
> struct bio *dio_bio;
> - u8 csum[0];
> };
>
> /*
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index be91397..40e9938 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -3739,8 +3739,7 @@ int btrfs_del_csums(struct btrfs_trans_handle *trans,
> int btrfs_lookup_bio_sums(struct btrfs_root *root, struct inode *inode,
> struct bio *bio, u32 *dst);
> int btrfs_lookup_bio_sums_dio(struct btrfs_root *root, struct inode *inode,
> - struct btrfs_dio_private *dip, struct bio *bio,
> - u64 logical_offset);
> + struct bio *bio, u64 logical_offset);
> int btrfs_insert_file_extent(struct btrfs_trans_handle *trans,
> struct btrfs_root *root,
> u64 objectid, u64 pos,
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index 23398ad..0fb63c4 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -2617,9 +2617,18 @@ btrfs_bio_alloc(struct block_device *bdev, u64 first_sector, int nr_vecs,
>
> struct bio *btrfs_bio_clone(struct bio *bio, gfp_t gfp_mask)
> {
> - return bio_clone_bioset(bio, gfp_mask, btrfs_bioset);
> -}
> + struct btrfs_io_bio *btrfs_bio;
> + struct bio *new;
>
> + new = bio_clone_bioset(bio, gfp_mask, btrfs_bioset);
> + if (new) {
> + btrfs_bio = btrfs_io_bio(new);
> + btrfs_bio->csum = NULL;
> + btrfs_bio->csum_allocated = NULL;
> + btrfs_bio->end_io = NULL;
> + }
> + return bio;
> +}
>
> /* this also allocates from the btrfs_bioset */
> struct bio *btrfs_io_bio_alloc(gfp_t gfp_mask, unsigned int nr_iovecs)
> diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
> index f46cfe4..cf1b94f 100644
> --- a/fs/btrfs/file-item.c
> +++ b/fs/btrfs/file-item.c
> @@ -299,19 +299,9 @@ int btrfs_lookup_bio_sums(struct btrfs_root *root, struct inode *inode,
> }
>
> int btrfs_lookup_bio_sums_dio(struct btrfs_root *root, struct inode *inode,
> - struct btrfs_dio_private *dip, struct bio *bio,
> - u64 offset)
> + struct bio *bio, u64 offset)
> {
> - int len = (bio->bi_iter.bi_sector << 9) - dip->disk_bytenr;
> - u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
> - int ret;
> -
> - len >>= inode->i_sb->s_blocksize_bits;
> - len *= csum_size;
> -
> - ret = __btrfs_lookup_bio_sums(root, inode, bio, offset,
> - (u32 *)(dip->csum + len), 1);
> - return ret;
> + return __btrfs_lookup_bio_sums(root, inode, bio, offset, NULL, 1);
> }
>
> int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 548489e..fd88126 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -7081,7 +7081,8 @@ static void btrfs_endio_direct_read(struct bio *bio, int err)
> struct inode *inode = dip->inode;
> struct btrfs_root *root = BTRFS_I(inode)->root;
> struct bio *dio_bio;
> - u32 *csums = (u32 *)dip->csum;
> + struct btrfs_io_bio *io_bio = btrfs_io_bio(bio);
> + u32 *csums = (u32 *)io_bio->csum;
> u64 start;
> int i;
>
> @@ -7123,6 +7124,9 @@ static void btrfs_endio_direct_read(struct bio *bio, int err)
> if (err)
> clear_bit(BIO_UPTODATE, &dio_bio->bi_flags);
> dio_end_io(dio_bio, err);
> +
> + if (io_bio->end_io)
> + io_bio->end_io(io_bio, err);
> bio_put(bio);
> }
>
> @@ -7261,13 +7265,20 @@ static inline int __btrfs_submit_dio_bio(struct bio *bio, struct inode *inode,
> ret = btrfs_csum_one_bio(root, inode, bio, file_offset, 1);
> if (ret)
> goto err;
> - } else if (!skip_sum) {
> - ret = btrfs_lookup_bio_sums_dio(root, inode, dip, bio,
> + } else {
> + /*
> + * We have loaded all the csum data we need when we submit
> + * the first bio, so skip it.
> + */
> + if (dip->logical_offset != file_offset)
> + goto map;
> +
> + /* Load all csum data at once. */
> + ret = btrfs_lookup_bio_sums_dio(root, inode, dip->orig_bio,
> file_offset);
> if (ret)
> goto err;
> }
> -
> map:
> ret = btrfs_map_bio(root, rw, bio, 0, async_submit);
> err:
> @@ -7288,7 +7299,7 @@ static int btrfs_submit_direct_hook(int rw, struct btrfs_dio_private *dip,
> u64 submit_len = 0;
> u64 map_length;
> int nr_pages = 0;
> - int ret = 0;
> + int ret;
> int async_submit = 0;
>
> map_length = orig_bio->bi_iter.bi_size;
> @@ -7392,11 +7403,10 @@ static void btrfs_submit_direct(int rw, struct bio *dio_bio,
> struct btrfs_root *root = BTRFS_I(inode)->root;
> struct btrfs_dio_private *dip;
> struct bio *io_bio;
> + struct btrfs_io_bio *btrfs_bio;
> int skip_sum;
> - int sum_len;
> int write = rw & REQ_WRITE;
> int ret = 0;
> - u16 csum_size;
>
> skip_sum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM;
>
> @@ -7406,16 +7416,7 @@ static void btrfs_submit_direct(int rw, struct bio *dio_bio,
> goto free_ordered;
> }
>
> - if (!skip_sum && !write) {
> - csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
> - sum_len = dio_bio->bi_iter.bi_size >>
> - inode->i_sb->s_blocksize_bits;
> - sum_len *= csum_size;
> - } else {
> - sum_len = 0;
> - }
> -
> - dip = kmalloc(sizeof(*dip) + sum_len, GFP_NOFS);
> + dip = kmalloc(sizeof(*dip), GFP_NOFS);
> if (!dip) {
> ret = -ENOMEM;
> goto free_io_bio;
> @@ -7441,6 +7442,9 @@ static void btrfs_submit_direct(int rw, struct bio *dio_bio,
> if (!ret)
> return;
>
> + btrfs_bio = btrfs_io_bio(io_bio);
> + if (btrfs_bio->end_io)
> + btrfs_bio->end_io(btrfs_bio, ret);
> free_io_bio:
> bio_put(io_bio);
>
> --
> 1.9.3
>
> --
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--
Filipe David Manana,
"Reasonable men adapt themselves to the world.
Unreasonable men adapt the world to themselves.
That's why all progress depends on unreasonable men."
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