On 26.11.19 г. 5:14 ч., Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
>
> Switch from __blockdev_direct_IO() to iomap_dio_rw().
> Rename btrfs_get_blocks_direct() to btrfs_dio_iomap_begin() and use it
> as iomap_begin() for iomap direct I/O functions. This function
> allocates and locks all the blocks required for the I/O.
> btrfs_submit_direct() is used as the submit_io() hook for direct I/O
> ops.
>
> Since we need direct I/O reads to go through iomap_dio_rw(), we change
> file_operations.read_iter() to a btrfs_file_read_iter() which calls
> btrfs_direct_IO() for direct reads and falls back to
> generic_file_buffered_read() for incomplete reads and buffered reads.
>
> We don't need address_space.direct_IO() anymore so set it to noop.
> Similarly, we don't need flags used in __blockdev_direct_IO(). iomap is
> capable of direct I/O reads from a hole, so we don't need to return
> -ENOENT.
>
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
> ---
> fs/btrfs/ctree.h | 2 +
> fs/btrfs/file.c | 15 ++++-
> fs/btrfs/inode.c | 171 ++++++++++++++++++++++++++-----------------------------
> 3 files changed, 97 insertions(+), 91 deletions(-)
>
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index fe2b8765d9e6..6f038ba34512 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -2903,6 +2903,8 @@ int btrfs_writepage_cow_fixup(struct page *page, u64 start, u64 end);
> void btrfs_writepage_endio_finish_ordered(struct page *page, u64 start,
> u64 end, int uptodate);
> extern const struct dentry_operations btrfs_dentry_operations;
> +ssize_t btrfs_dio_read(struct kiocb *iocb, struct iov_iter *iter);
> +ssize_t btrfs_dio_write(struct kiocb *iocb, struct iov_iter *iter);
>
> /* ioctl.c */
> long btrfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
> index 435a502a3226..960a0767f532 100644
> --- a/fs/btrfs/file.c
> +++ b/fs/btrfs/file.c
> @@ -1834,7 +1834,7 @@ static ssize_t __btrfs_direct_write(struct kiocb *iocb, struct iov_iter *from)
> loff_t endbyte;
> int err;
>
> - written = generic_file_direct_write(iocb, from);
> + written = btrfs_dio_write(iocb, from);
>
> if (written < 0 || !iov_iter_count(from))
> return written;
> @@ -3452,9 +3452,20 @@ static int btrfs_file_open(struct inode *inode, struct file *filp)
> return generic_file_open(inode, filp);
> }
>
> +static ssize_t btrfs_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
> +{
> + ssize_t ret = 0;
> + if (iocb->ki_flags & IOCB_DIRECT)
> + ret = btrfs_dio_read(iocb, to);
> + if (ret < 0)
> + return ret;
> +
> + return generic_file_buffered_read(iocb, to, ret);
> +}
> +
> const struct file_operations btrfs_file_operations = {
> .llseek = btrfs_file_llseek,
> - .read_iter = generic_file_read_iter,
> + .read_iter = btrfs_file_read_iter,
> .splice_read = generic_file_splice_read,
> .write_iter = btrfs_file_write_iter,
> .mmap = btrfs_file_mmap,
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 015910079e73..9a39a53b9068 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -29,6 +29,7 @@
> #include <linux/iversion.h>
> #include <linux/swap.h>
> #include <linux/sched/mm.h>
> +#include <linux/iomap.h>
> #include <asm/unaligned.h>
> #include "misc.h"
> #include "ctree.h"
> @@ -7619,28 +7620,7 @@ static struct extent_map *create_io_em(struct inode *inode, u64 start, u64 len,
> }
>
>
> -static int btrfs_get_blocks_direct_read(struct extent_map *em,
> - struct buffer_head *bh_result,
> - struct inode *inode,
> - u64 start, u64 len)
> -{
> - if (em->block_start == EXTENT_MAP_HOLE ||
> - test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
> - return -ENOENT;
> -
> - len = min(len, em->len - (start - em->start));
> -
> - bh_result->b_blocknr = (em->block_start + (start - em->start)) >>
> - inode->i_blkbits;
> - bh_result->b_size = len;
> - bh_result->b_bdev = em->bdev;
> - set_buffer_mapped(bh_result);
> -
> - return 0;
> -}
> -
> static int btrfs_get_blocks_direct_write(struct extent_map **map,
> - struct buffer_head *bh_result,
> struct inode *inode,
> struct btrfs_dio_data *dio_data,
> u64 start, u64 len)
> @@ -7702,7 +7682,6 @@ static int btrfs_get_blocks_direct_write(struct extent_map **map,
> }
>
> /* this will cow the extent */
> - len = bh_result->b_size;
> free_extent_map(em);
> *map = em = btrfs_new_extent_direct(inode, start, len);
> if (IS_ERR(em)) {
> @@ -7713,15 +7692,6 @@ static int btrfs_get_blocks_direct_write(struct extent_map **map,
> len = min(len, em->len - (start - em->start));
>
> skip_cow:
> - bh_result->b_blocknr = (em->block_start + (start - em->start)) >>
> - inode->i_blkbits;
> - bh_result->b_size = len;
> - bh_result->b_bdev = em->bdev;
> - set_buffer_mapped(bh_result);
> -
> - if (!test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
> - set_buffer_new(bh_result);
> -
> /*
> * Need to update the i_size under the extent lock so buffered
> * readers will get the updated i_size when we unlock.
> @@ -7737,17 +7707,19 @@ static int btrfs_get_blocks_direct_write(struct extent_map **map,
> return ret;
> }
>
> -static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
> - struct buffer_head *bh_result, int create)
> +static int btrfs_dio_iomap_begin(struct inode *inode, loff_t start,
> + loff_t length, unsigned flags, struct iomap *iomap,
> + struct iomap *srcmap)
> {
> struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
> struct extent_map *em;
> struct extent_state *cached_state = NULL;
> struct btrfs_dio_data *dio_data = NULL;
> - u64 start = iblock << inode->i_blkbits;
> u64 lockstart, lockend;
> - u64 len = bh_result->b_size;
> + int create = flags & IOMAP_WRITE;
> int ret = 0;
> + u64 len = length;
> + bool unlock_extents = false;
>
> if (!create)
> len = min_t(u64, len, fs_info->sectorsize);
> @@ -7755,6 +7727,17 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
> lockstart = start;
> lockend = start + len - 1;
>
> + /*
> + * The generic stuff only does filemap_write_and_wait_range, which
> + * isn't enough if we've written compressed pages to this area, so
> + * we need to flush the dirty pages again to make absolutely sure
> + * that any outstanding dirty pages are on disk.
> + */
> + if (test_bit(BTRFS_INODE_HAS_ASYNC_EXTENT,
> + &BTRFS_I(inode)->runtime_flags))
> + ret = filemap_fdatawrite_range(inode->i_mapping, start,
> + start + length - 1);
> +
> if (current->journal_info) {
> /*
> * Need to pull our outstanding extents and set journal_info to NULL so
> @@ -7803,35 +7786,45 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
> }
>
> if (create) {
> - ret = btrfs_get_blocks_direct_write(&em, bh_result, inode,
> + ret = btrfs_get_blocks_direct_write(&em, inode,
> dio_data, start, len);
> if (ret < 0)
> goto unlock_err;
> -
> - unlock_extent_cached(&BTRFS_I(inode)->io_tree, lockstart,
> - lockend, &cached_state);
> + unlock_extents = true;
> + } else if (em->block_start == EXTENT_MAP_HOLE ||
> + test_bit(EXTENT_FLAG_PREALLOC, &em->flags)) {
> + /* Unlock in case of direct reading from a hole */
> + unlock_extents = true;
> } else {
> - ret = btrfs_get_blocks_direct_read(em, bh_result, inode,
> - start, len);
> - /* Can be negative only if we read from a hole */
> - if (ret < 0) {
> - ret = 0;
> - free_extent_map(em);
> - goto unlock_err;
> - }
> +
> + len = min(len, em->len - (start - em->start));
> /*
> * We need to unlock only the end area that we aren't using.
> * The rest is going to be unlocked by the endio routine.
> */
> - lockstart = start + bh_result->b_size;
> - if (lockstart < lockend) {
> - unlock_extent_cached(&BTRFS_I(inode)->io_tree,
> - lockstart, lockend, &cached_state);
> - } else {
> + lockstart = start + len;
> + if (lockstart < lockend)
> + unlock_extents = true;
> + else
> free_extent_state(cached_state);
> - }
> }
>
> + if (unlock_extents)
> + unlock_extent_cached(&BTRFS_I(inode)->io_tree,
> + lockstart, lockend, &cached_state);
> +
> + if ((em->block_start == EXTENT_MAP_HOLE) ||
> + (test_bit(EXTENT_FLAG_PREALLOC, &em->flags) && !create)) {
> + iomap->addr = IOMAP_NULL_ADDR;
> + iomap->type = IOMAP_HOLE;
> + } else {
> + iomap->addr = em->block_start;
> + iomap->type = IOMAP_MAPPED;
> + }
> + iomap->offset = em->start;
> + iomap->bdev = em->bdev;
> + iomap->length = em->len;
> +
So here you always return a full extent worth of data, why not trimming
it to the requested range? I think this is still correct because the
generic iomap infrastructure will only process the requested range, at
least as far as iomap->length is concerned. But I'm not so sure about
iomap->offset though.
