On 9/5/18 8:57 AM, Carlos Maiolino wrote:
> This patch modifies ioctl_fibmap to use FIEMAP interface internally. The
> FIBMAP API is not changed, but now ->bmap can go.
Not really, because you still call it if ->fiemap isn't there ;)
>
> Signed-off-by: Carlos Maiolino <cmaiolino@xxxxxxxxxx>
> ---
> fs/inode.c | 38 +++++++++++++++++++++++++++++++++++++-
> fs/ioctl.c | 11 +++++++++--
> include/uapi/linux/fiemap.h | 1 +
> 3 files changed, 47 insertions(+), 3 deletions(-)
>
> diff --git a/fs/inode.c b/fs/inode.c
> index 41812a3e829e..07befc5f253b 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -1588,9 +1588,45 @@ EXPORT_SYMBOL(iput);
> */
> sector_t bmap(struct inode *inode, sector_t block)
> {
> +
> + struct fiemap_extent_info fieinfo = { 0, };
> + struct fiemap_extent fextent;
> + u64 start = block << inode->i_blkbits;
> + int error;
> sector_t res = 0;
> - if (inode->i_mapping->a_ops->bmap)
> +
> + if (inode->i_op->fiemap) {
> + fextent.fe_logical = 0;
> + fextent.fe_physical = 0;
> + fieinfo.fi_flags = FIEMAP_KERNEL_FIBMAP;
| FIEMAP_FLAG_SYNC?
> + fieinfo.fi_extents_max = 1;
> + fieinfo.fi_extents_start = (__force struct fiemap_extent __user *) &fextent;
> +
> + error = inode->i_op->fiemap(inode, &fieinfo, start, 1);
> +
> + /* FIBMAP expect a zero return for error */
> + if (error)
> + goto out;
do you need to test fieinfo.fi_extents_mapped > 0? I don't know if it's
possible to return error == 0 && fi_extents_mapped == 0, TBH.
> +
> + /*
> + * Fiemap implementation of some filesystems will return the
> + * extent map beginning at the requested offset
> + * (fextent.fi_logical == start), while other FSes will return
> + * the beginning of the extent at fextent.fe_logical, even if
> + * the requested offset is somehwere in the middle of the
> + * extent. We must be sure to return the correct block block
> + * here in both cases.
> + */
> + if (fextent.fe_logical != start)
> + res = (fextent.fe_physical + start) >> inode->i_blkbits;
I don't think this is correct, is it? You can't add the entire requested
logical file offset (start) to the resulting physical extent start (fe_physical).
You'd need to add the delta, (start - fextent.fe_logical) to the physical extent
start to get the offset into the mapping, right?
res = (fextent.fe_physical +
(start - fextent.fe_logical)) >> inode->i_blkbits;
You'll also need to test the resulting fm_flags to be sure that
this is something that's valid to return via FIBMAP.
For example, you might get a shared block, which we have recently learned
Must Not Be Provided Under Any Circumstances to userspace via FIBMAP.
(I'm still thinking about how this change is structured in general, but I think
the above are a few logical issues w/ the code.)
-Eric
> + else
> + res = fextent.fe_physical >> inode->i_blkbits;
> +
> + } else if (inode->i_mapping->a_ops->bmap) {
> res = inode->i_mapping->a_ops->bmap(inode->i_mapping, block);
> + }
> +
> +out:
> return res;
> }
> EXPORT_SYMBOL(bmap);
> diff --git a/fs/ioctl.c b/fs/ioctl.c
> index 413585d58415..58de1dd507b1 100644
> --- a/fs/ioctl.c
> +++ b/fs/ioctl.c
> @@ -117,8 +117,14 @@ int fiemap_fill_next_extent(struct fiemap_extent_info *fieinfo, u64 logical,
> extent.fe_flags = flags;
>
> dest += fieinfo->fi_extents_mapped;
> - if (copy_to_user(dest, &extent, sizeof(extent)))
> - return -EFAULT;
> +
> + if (fieinfo->fi_flags & FIEMAP_KERNEL_FIBMAP) {
> + memcpy((__force struct fiemap_extent *)dest, &extent,
> + sizeof(extent));
> + } else {
> + if (copy_to_user(dest, &extent, sizeof(extent)))
> + return -EFAULT;
> + }
>
> fieinfo->fi_extents_mapped++;
> if (fieinfo->fi_extents_mapped == fieinfo->fi_extents_max)
> @@ -146,6 +152,7 @@ int fiemap_check_flags(struct fiemap_extent_info *fieinfo, u32 fs_flags)
> u32 incompat_flags;
>
> incompat_flags = fieinfo->fi_flags & ~(FIEMAP_FLAGS_COMPAT & fs_flags);
> + incompat_flags &= ~(FIEMAP_KERNEL_FIBMAP);
> if (incompat_flags) {
> fieinfo->fi_flags = incompat_flags;
> return -EBADR;
> diff --git a/include/uapi/linux/fiemap.h b/include/uapi/linux/fiemap.h
> index 8c0bc24d5d95..7064a3fa5421 100644
> --- a/include/uapi/linux/fiemap.h
> +++ b/include/uapi/linux/fiemap.h
> @@ -42,6 +42,7 @@ struct fiemap {
> #define FIEMAP_FLAG_SYNC 0x00000001 /* sync file data before map */
> #define FIEMAP_FLAG_XATTR 0x00000002 /* map extended attribute tree */
> #define FIEMAP_FLAG_CACHE 0x00000004 /* request caching of the extents */
> +#define FIEMAP_KERNEL_FIBMAP 0x00000008 /* Use FIEMAP for FIBMAP */
>
> #define FIEMAP_FLAGS_COMPAT (FIEMAP_FLAG_SYNC | FIEMAP_FLAG_XATTR)
>
>
