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Re: [Qemu-block] [PATCH 1/7] block: fix comment for bdrv_get_allocated_f
Re: [Qemu-block] [PATCH 1/7] block: fix comment for bdrv_get_allocated_file_size()
Thu, 25 May 2017 11:32:14 -0500
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On 05/25/2017 10:26 AM, Vladimir Sementsov-Ogievskiy wrote:
> Current comment is not clear enough: which sparseness is meant, coming
> from sparse image format or from sparse file system?
> For example, if we have qcow2 above raw file on non-sparse file system,
> this function will say nothing about unallocated (by qcow2 layer)
> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> block.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
> diff --git a/block.c b/block.c
> index 50ba264143..ba22fc0dfb 100644
> --- a/block.c
> +++ b/block.c
> @@ -3388,8 +3388,8 @@ int bdrv_truncate(BdrvChild *child, int64_t offset,
> Error **errp)
> - * Length of a allocated file in bytes. Sparse files are counted by actual
Yay for getting rid of bad grammar (s/a /an /)
> - * allocated space. Return < 0 if error or unknown.
> + * Size of allocated in underlying file system area. Sparseness is taken into
Doesn't read well. Maybe: s/Size of allocated/Allocation size/ ?
> + * account for sparse file systems. Return < 0 if error or unknown.
I still don't get what we are trying to present.
If we have the following 6 qcow2 file clusters backed by the underlying
lseek(SEEK_DATA/HOLE) file system contents:
Then is our answer the size of all qcow2 allocations regardless of
underlying status (4, due to clusters 3-6), or the size of only the
clusters that read from the backing file (2, due to clusters 5-6), or
the size of only the clusters that currently occupy space in the file
system (2, due to clusters 4 and 6), or the size of clusters that are
not provably read-as-zero (1, due to cluster 6)?
Does the answer change if you can have underlying holes happen at a
smaller granularity than clusters?
What happens for compressed clusters?
I think we still need to do a better job at writing a precise comment.
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
Description: OpenPGP digital signature
[Qemu-block] [PATCH 6/7] qemu-img check: add file-size, Vladimir Sementsov-Ogievskiy, 2017/05/25
[Qemu-block] [PATCH 1/7] block: fix comment for bdrv_get_allocated_file_size(), Vladimir Sementsov-Ogievskiy, 2017/05/25
- Re: [Qemu-block] [PATCH 4/7] common: make get_human_readable_size public, (continued)
- Re: [Qemu-block] [PATCH 1/7] block: fix comment for bdrv_get_allocated_file_size(),
Eric Blake <=