Re: [libvirt] [PATCH 3/4] vol-info: Check for NFS FS type
On 08/08/2014 07:07 AM, Ján Tomko wrote:
On 08/05/2014 04:38 PM, John Ferlan wrote:
> https://bugzilla.redhat.com/show_bug.cgi?id=1077068
>
> Check for the NFS FS type being true for a "local" stat of the file
> to force usage of the 'st_size' value rather than calculating the size
> using the 'st_blocks' and 'st_blksize'. As described in the stat(2)
> man page:
>
> "Use of the st_blocks and st_blksize fields may be less portable."
>
> experimentation shows a 10M file could get the following output from stat:
>
> st_size=10485760 st_blocks=88 st_blksize=1048576
>
> resulting in a "44 KiB" value being displayed as the allocation value.
> While this value does match the "du -s" value of the same file, the
> "du -b" value shows the "st_size" field. Similarly a long listing
of the
> file shows the 10M size.
Capacity should be the apparent size (what du -b shows, or st_size), while
allocation should track the on-disk usage (du, st_blocks * 512).
It looks to me that the values are correct, it's just that posix_fallocate
does neither work nor fail on NFS.
Jan
Testing seems to indicate that posix_fallocate() either doesn't work as
expected on the target or using the target.path is incorrect...
Before posix_fallocate
stat st_blocks=0 st_blksize=1048576 st_size=10485760
lseek end=10485760
posix_fallocate of 10485760 bytes on /home/nfs_pool/target/test-vol1
After posix_fallocate
stat st_blocks=88 st_blksize=1048576 st_size=10485760
lseek end=10485760
Hmm... would going at the target be correct in this instance? Same test
but use the source path:
Before posix_fallocate
stat st_blocks=0 st_blksize=4096 st_size=10485760
lseek end=10485760
posix_fallocate of 10485760 bytes on /home/nfs_pool/nfs-export/test-vol1
After posix_fallocate
stat st_blocks=20480 st_blksize=4096 st_size=10485760
lseek end=10485760
...
hmm.... 20480 * 512 = 10485760
# df
...
localhost:/home/nfs_pool/nfs-export 140979200 35521536 98273280 27%
/home/nfs_pool/target
#
John