On Apr 17, 2018, at 1:19 PM, Darrick J. Wong <darrick.wong@xxxxxxxxxx> wrote:
>
> From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
> Now that block devices support PUNCH_HOLE via fallocate, refactor the
> unix_discard code into a helper that will always try to use it. For
> block devices we can fall back to BLKDISCARD, but we prefer to use
> fallocate because it will always invalidate the page cache of the zeroed
> region.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Reviewed-by: Andreas Dilger <adilger@xxxxxxxxx>
> ---
> lib/ext2fs/unix_io.c | 61 ++++++++++++++++++++++++++++++--------------------
> 1 file changed, 36 insertions(+), 25 deletions(-)
>
>
> diff --git a/lib/ext2fs/unix_io.c b/lib/ext2fs/unix_io.c
> index 1fb6279..0cf8ca2 100644
> --- a/lib/ext2fs/unix_io.c
> +++ b/lib/ext2fs/unix_io.c
> @@ -1073,6 +1073,38 @@ static errcode_t unix_set_option(io_channel channel, const char *option,
> #define BLKDISCARD _IO(0x12,119)
> #endif
>
> +/*
> + * Try a PUNCH_HOLE to unmap blocks, then BLKDISCARD if that doesn't work.
> + * We prefer PUNCH_HOLE because it invalidates the page cache, even on block
> + * devices.
> + */
> +static int __unix_discard(int fd, int is_bdev, off_t offset, off_t len)
> +{
> +#ifdef BLKDISCARD
> + __u64 range[2];
> +#endif
> + int ret = -1;
> +
> +#if defined(HAVE_FALLOCATE) && defined(FALLOC_FL_PUNCH_HOLE) && defined(FALLOC_FL_KEEP_SIZE)
> + ret = fallocate(fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
> + offset, len);
> + if (ret == 0)
> + return 0;
> +#endif
> +#ifdef BLKDISCARD
> + if (is_bdev) {
> + range[0] = (__u64)offset;
> + range[1] = (__u64)len;
> +
> + ret = ioctl(fd, BLKDISCARD, &range);
> + if (ret == 0)
> + return 0;
> + }
> +#endif
> + errno = EOPNOTSUPP;
> + return ret;
> +}
> +
> static errcode_t unix_discard(io_channel channel, unsigned long long block,
> unsigned long long count)
> {
> @@ -1083,31 +1115,10 @@ static errcode_t unix_discard(io_channel channel, unsigned long long block,
> data = (struct unix_private_data *) channel->private_data;
> EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);
>
> - if (channel->flags & CHANNEL_FLAGS_BLOCK_DEVICE) {
> -#ifdef BLKDISCARD
> - __u64 range[2];
> -
> - range[0] = (__u64)(block) * channel->block_size + data->offset;
> - range[1] = (__u64)(count) * channel->block_size;
> -
> - ret = ioctl(data->dev, BLKDISCARD, &range);
> -#else
> - goto unimplemented;
> -#endif
> - } else {
> -#if defined(HAVE_FALLOCATE) && defined(FALLOC_FL_PUNCH_HOLE)
> - /*
> - * If we are not on block device, try to use punch hole
> - * to reclaim free space.
> - */
> - ret = fallocate(data->dev,
> - FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
> - (off_t)(block) * channel->block_size + data->offset,
> - (off_t)(count) * channel->block_size);
> -#else
> - goto unimplemented;
> -#endif
> - }
> + ret = __unix_discard(data->dev,
> + (channel->flags & CHANNEL_FLAGS_BLOCK_DEVICE),
> + (off_t)(block) * channel->block_size + data->offset,
> + (off_t)(count) * channel->block_size);
> if (ret < 0) {
> if (errno == EOPNOTSUPP)
> goto unimplemented;
>
Cheers, Andreas
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