On Thu, Feb 22, 2018 at 06:12:13PM +0200, Nikolay Borisov wrote:
> Currently this function handles both the READ and WRITE dio cases. This
> is facilitated by a bunch of 'if' statements, a goto short-circuit
> statement and a very perverse aliasing of "!created"(READ) case
> by setting lockstart = lockend and checking for lockstart < lockend for
> detecting the write. Let's simplify this mess by extracting the
> READ-only code into a separate __btrfs_get_block_direct_read function.
> This is only the first step, the next one will be to factor out the
> write side as well. The end goal will be to have the common locking/
> unlocking code in btrfs_get_blocks_direct and then it will call either
> the read|write subvariants. No functional changes.
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
uh what a convoluted code to untangle. A few style notes below.
>
> Signed-off-by: Nikolay Borisov <nborisov@xxxxxxxx>
> ---
> fs/btrfs/inode.c | 49 ++++++++++++++++++++++++++++++++++++-------------
> 1 file changed, 36 insertions(+), 13 deletions(-)
>
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 491a7397f6fa..fd99347d0c91 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -7677,6 +7677,27 @@ static struct extent_map *create_io_em(struct inode *inode, u64 start, u64 len,
> return em;
> }
>
> +
> +static int __btrfs_get_blocks_direct_read(struct extent_map *em,
Please drop the "__" the function is static and there's no
underscore-less version.
> + 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(struct inode *inode, sector_t iblock,
> struct buffer_head *bh_result, int create)
> {
> @@ -7745,11 +7766,22 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
> goto unlock_err;
> }
>
> - /* Just a good old fashioned hole, return */
> - if (!create && (em->block_start == EXTENT_MAP_HOLE ||
> - test_bit(EXTENT_FLAG_PREALLOC, &em->flags))) {
> + if (!create) {
> + 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;
> + }
> + /*
> + * We need to unlock only the end area that we aren't using
> + * if there is any leftover space
> + */
> + free_extent_state(cached_state);
> free_extent_map(em);
> - goto unlock_err;
> + return 0;
Please add a separate label for that, the funcion uses the single exit
block style (labels and one-or-two returns).
> }
>
> /*
> @@ -7761,12 +7793,6 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
> * just use the extent.
> *
> */
> - if (!create) {
> - len = min(len, em->len - (start - em->start));
> - lockstart = start + len;
> - goto unlock;
> - }
> -
> if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags) ||
> ((BTRFS_I(inode)->flags & BTRFS_INODE_NODATACOW) &&
> em->block_start != EXTENT_MAP_HOLE)) {
> @@ -7853,10 +7879,7 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
> clear_extent_bit(&BTRFS_I(inode)->io_tree, lockstart,
> lockend, unlock_bits, 1, 0,
> &cached_state);
> - } else {
> - free_extent_state(cached_state);
> }
> -
> free_extent_map(em);
>
> return 0;
--
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