[PATCH 08/14] fs: iomap based fiemap implementation

[Andreas Grünbacher]

Christoph,

2016-06-01 16:44 GMT+02:00 Christoph Hellwig <hch at lst.de>:
> Add a simple fiemap implementation based on iomap_ops, partially based
> on a previous implementation from Bob Peterson <rpeterso at redhat.com>.
>
> Signed-off-by: Christoph Hellwig <hch at lst.de>
> ---
>  fs/iomap.c            | 90 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/iomap.h |  3 ++
>  2 files changed, 93 insertions(+)
>
> diff --git a/fs/iomap.c b/fs/iomap.c
> index e51adb6..e874c78 100644
> --- a/fs/iomap.c
> +++ b/fs/iomap.c
> @@ -405,3 +405,93 @@ out_unlock:
>         return ret;
>  }
>  EXPORT_SYMBOL_GPL(iomap_page_mkwrite);
> +
> +struct fiemap_ctx {
> +       struct fiemap_extent_info *fi;
> +       struct iomap prev;
> +};
> +
> +static int iomap_to_fiemap(struct fiemap_extent_info *fi,
> +               struct iomap *iomap, u32 flags)
> +{
> +       switch (iomap->type) {
> +       case IOMAP_HOLE:
> +               /* skip holes */
> +               return 0;
> +       case IOMAP_DELALLOC:
> +               flags |= FIEMAP_EXTENT_DELALLOC | FIEMAP_EXTENT_UNKNOWN;
> +               break;
> +       case IOMAP_UNWRITTEN:
> +               flags |= FIEMAP_EXTENT_UNWRITTEN;
> +               break;
> +       case IOMAP_MAPPED:
> +               break;
> +       }
> +
> +       return fiemap_fill_next_extent(fi, iomap->offset,
> +                       iomap->blkno != IOMAP_NULL_BLOCK ? iomap->blkno << 9: 0,
> +                       iomap->length, flags | FIEMAP_EXTENT_MERGED);

According to Documentation/filesystems/fiemap.txt, it seems that
FIEMAP_EXTENT_MERGED flag should only be set by filesystems with
block-based rather than extent-based allocation. Am I overlooking
something?

> +
> +}
> +
> +static loff_t
> +iomap_fiemap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> +               struct iomap *iomap)
> +{
> +       struct fiemap_ctx *ctx = data;
> +       loff_t ret = length;
> +
> +       if (iomap->type == IOMAP_HOLE)
> +               return length;
> +
> +       ret = iomap_to_fiemap(ctx->fi, &ctx->prev, 0);
> +       ctx->prev = *iomap;
> +       switch (ret) {
> +       case 0:         /* success */
> +               return length;
> +       case 1:         /* extent array full */
> +               return 0;
> +       default:
> +               return ret;
> +       }
> +}
> +
> +int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fi,
> +               loff_t start, loff_t len, struct iomap_ops *ops)
> +{
> +       struct fiemap_ctx ctx;
> +       loff_t ret;
> +
> +       memset(&ctx, 0, sizeof(ctx));
> +       ctx.fi = fi;
> +       ctx.prev.type = IOMAP_HOLE;
> +
> +       ret = fiemap_check_flags(fi, FIEMAP_FLAG_SYNC);
> +       if (ret)
> +               return ret;
> +
> +       ret = filemap_write_and_wait(inode->i_mapping);
> +       if (ret)
> +               return ret;
> +
> +       while (len > 0) {
> +               ret = iomap_apply(inode, start, len, 0, ops, &ctx,
> +                               iomap_fiemap_actor);
> +               if (ret < 0)
> +                       return ret;
> +               if (ret == 0)
> +                       break;
> +
> +               start += ret;
> +               len -= ret;
> +       }
> +
> +       if (ctx.prev.type != IOMAP_HOLE) {
> +               ret = iomap_to_fiemap(fi, &ctx.prev, FIEMAP_EXTENT_LAST);
> +               if (ret < 0)
> +                       return ret;
> +       }
> +
> +       return 0;
> +}
> +EXPORT_SYMBOL_GPL(iomap_fiemap);
> diff --git a/include/linux/iomap.h b/include/linux/iomap.h
> index 854766f..b3deee1 100644
> --- a/include/linux/iomap.h
> +++ b/include/linux/iomap.h
> @@ -3,6 +3,7 @@
>
>  #include <linux/types.h>
>
> +struct fiemap_extent_info;
>  struct inode;
>  struct iov_iter;
>  struct kiocb;
> @@ -63,5 +64,7 @@ int iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
>                 struct iomap_ops *ops);
>  int iomap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
>                 struct iomap_ops *ops);
> +int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
> +               loff_t start, loff_t len, struct iomap_ops *ops);
>
>  #endif /* LINUX_IOMAP_H */
> --
> 2.1.4
>
> --
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Thanks,
Andreas