Hi Ted,
> commit aca92ff6f57c000d1b4523e383c8bd6b8269b8b1
> Author: Leonard Michlmayr<leonard.michlmayr@xxxxxxxxx>
> Date: Thu Mar 4 17:07:28 2010 -0500
>
> ext4: correctly calculate number of blocks for fiemap
>
> ext4_fiemap() rounds the length of the requested range down to
> blocksize, which is is not the true number of blocks that cover the
> requested region. This problem is especially impressive if the user
> requests only the first byte of a file: not a single extent will be
> reported.
>
> We fix this by calculating the last block of the region and then
> subtract to find the number of blocks in the extents.
>
> Signed-off-by: Leonard Michlmayr<leonard.michlmayr@xxxxxxxxx>
> Signed-off-by: "Theodore Ts'o"<tytso@xxxxxxx>
>
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index bd80891..7d54850 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -3768,7 +3768,6 @@ int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
> __u64 start, __u64 len)
> {
> ext4_lblk_t start_blk;
> - ext4_lblk_t len_blks;
> int error = 0;
>
> /* fallback to generic here if not in extents fmt */
> @@ -3782,8 +3781,14 @@ int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
> if (fieinfo->fi_flags& FIEMAP_FLAG_XATTR) {
> error = ext4_xattr_fiemap(inode, fieinfo);
> } else {
> + ext4_lblk_t len_blks;
> + __u64 last_blk;
> +
> start_blk = start>> inode->i_sb->s_blocksize_bits;
> - len_blks = len>> inode->i_sb->s_blocksize_bits;
> + last_blk = (start + len - 1)>> inode->i_sb->s_blocksize_bits;
> + if (last_blk>= EXT_MAX_BLOCK)
> + last_blk = EXT_MAX_BLOCK-1;
last_blk = EXT_MAX_BLOCK - 1;
You seem to have already pushed this patch to Linus, though.
There is a coding style thing.
Anyway, the patch works fine for me.
Thanks for your work. :-)
Tested-by: Akira Fujita <a-fujita@xxxxxxxxxxxxx>
Regards,
Akira Fujita
> + len_blks = ((ext4_lblk_t) last_blk) - start_blk + 1;
>
> /*
> * Walk the extent tree gathering extent information.
>
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