So depending on the file sizes and with strict allocate enabled in
smb.conf it does shrink the file (I will also experiment with e.g.
allocation roundup size)
What I was trying to do was extend allocation for a 4MB file to 5.4MB,
shrink it to 10K (which ended up shrinking it to 1MB for the Samba
case).
[sfrench@localhost cifs-2.6]$ stat /mnt/test/4M ; fallocate -n -l
5400000 /mnt/test/4M ; sleep 3 ; stat /mnt/test/4M ; fallocate -n -l
10000 /mnt/test/4M ; sleep 2; stat /mnt/test/4M
File: ‘/mnt/test/4M’
Size: 4194304 Blocks: 8192 IO Block: 16384 regular file
Device: 26h/38d Inode: 393820 Links: 1
Access: (0755/-rwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root)
Context: system_u:object_r:cifs_t:s0
Access: 2014-07-21 14:19:30.596249500 -0500
Modify: 2014-07-21 14:19:30.731591000 -0500
Change: 2014-07-21 14:19:30.731591000 -0500
Birth: -
File: ‘/mnt/test/4M’ (after fallocate 5400000)
Size: 4194304 Blocks: 8192 IO Block: 16384 regular file
Device: 26h/38d Inode: 393820 Links: 1
Access: (0755/-rwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root)
Context: system_u:object_r:cifs_t:s0
Access: 2014-07-21 14:19:30.596249500 -0500
Modify: 2014-07-21 14:20:17.141270500 -0500
Change: 2014-07-21 14:20:17.141270500 -0500
Birth: -
File: ‘/mnt/test/4M’ (after fallocate 10000)
Size: 1048576 Blocks: 2048 IO Block: 16384 regular file
Device: 26h/38d Inode: 393820 Links: 1
Access: (0755/-rwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root)
Context: system_u:object_r:cifs_t:s0
Access: 2014-07-21 14:19:30.596249500 -0500
Modify: 2014-07-21 14:20:20.157755800 -0500
Change: 2014-07-21 14:20:20.157755800 -0500
Birth: -
(I will send jra the wireshark trace).
On Mon, Jul 21, 2014 at 1:55 PM, Jeremy Allison <jra@xxxxxxxxx> wrote:
> On Mon, Jul 21, 2014 at 01:43:12PM -0500, Steve French wrote:
>> What about shrinking the file to the wrong size?
>
> In the set allocation path info it's going through:
>
> if (allocation_size) {
> allocation_size = smb_roundup(conn, allocation_size);
> }
>
> which by default uses 1MB allocation roundup values.
>
> If you need to set the file length, set the file length :-).
>
> It's arguable if the server can mess with allocation
> requests on file shrink, but this hasn't caused a
> problem in the SMB1/Windows SMB2 code paths so far,
> so I'm guessing it might be allowable....
>
> More research needed !
--
Thanks,
Steve
--
To unsubscribe from this list: send the line "unsubscribe linux-cifs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
