| Message ID | 20220315161959.19453-4-lhenriques@suse.de |
|---|---|
| State | Superseded |
| Headers | show |
| Series | ceph: add support for snapshot names encryption | expand |
On 3/16/22 12:19 AM, Luís Henriques wrote: > Signed-off-by: Luís Henriques <lhenriques@suse.de> > --- > Documentation/filesystems/ceph.rst | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/Documentation/filesystems/ceph.rst b/Documentation/filesystems/ceph.rst > index 4942e018db85..d487cabe792d 100644 > --- a/Documentation/filesystems/ceph.rst > +++ b/Documentation/filesystems/ceph.rst > @@ -57,6 +57,16 @@ a snapshot on any subdirectory (and its nested contents) in the > system. Snapshot creation and deletion are as simple as 'mkdir > .snap/foo' and 'rmdir .snap/foo'. > > +Snapshot names have two limitations: > + > +* They can not start with an underscore ('_'), as these names are reserved > + for internal usage by the MDS. > +* They can not exceed 240 characters in size. This is because the MDS makes > + use of long snapshot names internally, which follow the format: > + `_<SNAPSHOT-NAME>_<INODE-NUMBER>`. Since filenames in general can't have > + more than 255 characters, and `<node-id>` takes 13 characters, the long > + snapshot names can take as much as 255 - 1 - 1 - 13 = 240. > + > Ceph also provides some recursive accounting on directories for nested > files and bytes. That is, a 'getfattr -d foo' on any directory in the > system will reveal the total number of nested regular files and > LGTM. Reviewed-by: Xiubo Li <xiubli@redhat.com>
diff --git a/Documentation/filesystems/ceph.rst b/Documentation/filesystems/ceph.rst index 4942e018db85..d487cabe792d 100644 --- a/Documentation/filesystems/ceph.rst +++ b/Documentation/filesystems/ceph.rst @@ -57,6 +57,16 @@ a snapshot on any subdirectory (and its nested contents) in the system. Snapshot creation and deletion are as simple as 'mkdir .snap/foo' and 'rmdir .snap/foo'. +Snapshot names have two limitations: + +* They can not start with an underscore ('_'), as these names are reserved + for internal usage by the MDS. +* They can not exceed 240 characters in size. This is because the MDS makes + use of long snapshot names internally, which follow the format: + `_<SNAPSHOT-NAME>_<INODE-NUMBER>`. Since filenames in general can't have + more than 255 characters, and `<node-id>` takes 13 characters, the long + snapshot names can take as much as 255 - 1 - 1 - 13 = 240. + Ceph also provides some recursive accounting on directories for nested files and bytes. That is, a 'getfattr -d foo' on any directory in the system will reveal the total number of nested regular files and
Signed-off-by: Luís Henriques <lhenriques@suse.de> --- Documentation/filesystems/ceph.rst | 10 ++++++++++ 1 file changed, 10 insertions(+)