Re: CephFS "move" operation

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Mhhhm... that's funny, I checked an mv with an strace now. I get:
---------------------------------------------------------------------------------
access("/cephfs/some_folder/file", W_OK) = 0
rename("foo", "/cephfs/some_folder/file") = -1 EXDEV (Invalid cross-device link)
unlink("/cephfs/some_folder/file") = 0
lgetxattr("foo", "security.selinux", "system_u:object_r:fusefs_t:s0", 255) = 30
---------------------------------------------------------------------------------
But I can assure it's only a single filesystem, and a single ceph-fuse client running. 

Same happens when using absolute paths. 

Cheers,
	Oliver

Am 25.05.2018 um 15:06 schrieb Ric Wheeler:
> We should look at what mv uses to see if it thinks the directories are on different file systems.
> 
> If the fstat or whatever it looks at is confused, that might explain it.
> 
> Ric
> 
> 
> On Fri, May 25, 2018, 9:04 AM Oliver Freyermuth <freyermuth@xxxxxxxxxxxxxxxxxx <mailto:freyermuth@xxxxxxxxxxxxxxxxxx>> wrote:
> 
>     Am 25.05.2018 um 14:57 schrieb Ric Wheeler:
>     > Is this move between directories on the same file system?
> 
>     It is, we only have a single CephFS in use. There's also only a single ceph-fuse client running.
> 
>     What's different, though, are different ACLs set for source and target directory, and owner / group,
>     but I hope that should not matter.
> 
>     All the best,
>     Oliver
> 
>     > Rename as a system call only works within a file system.
>     >
>     > The user space mv command becomes a copy when not the same file system. 
>     >
>     > Regards,
>     >
>     > Ric
>     >
>     >
>     > On Fri, May 25, 2018, 8:51 AM John Spray <jspray@xxxxxxxxxx <mailto:jspray@xxxxxxxxxx> <mailto:jspray@xxxxxxxxxx <mailto:jspray@xxxxxxxxxx>>> wrote:
>     >
>     >     On Fri, May 25, 2018 at 1:10 PM, Oliver Freyermuth
>     >     <freyermuth@xxxxxxxxxxxxxxxxxx <mailto:freyermuth@xxxxxxxxxxxxxxxxxx> <mailto:freyermuth@xxxxxxxxxxxxxxxxxx <mailto:freyermuth@xxxxxxxxxxxxxxxxxx>>> wrote:
>     >     > Dear Cephalopodians,
>     >     >
>     >     > I was wondering why a simple "mv" is taking extraordinarily long on CephFS and must note that,
>     >     > at least with the fuse-client (12.2.5) and when moving a file from one directory to another,
>     >     > the file appears to be copied first (byte by byte, traffic going through the client?) before the initial file is deleted.
>     >     >
>     >     > Is this true, or am I missing something?
>     >
>     >     A mv should not involve copying a file through the client -- it's
>     >     implemented in the MDS as a rename from one location to another.
>     >     What's the observation that's making it seem like the data is going
>     >     through the client?
>     >
>     >     John
>     >
>     >     >
>     >     > For large files, this might be rather time consuming,
>     >     > and we should certainly advise all our users to not move files around needlessly if this is the case.
>     >     >
>     >     > Cheers,
>     >     >         Oliver
>     >     >
>     >     >
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