On Thu, Apr 26, 2012 at 9:25 AM, David Howells <dhowells@xxxxxxxxxx> wrote: > Steve French <smfrench@xxxxxxxxx> wrote: > >> Would it be better to make the stable vs volatile inode number an attribute >> of the volume or something returned by the proposed xstat? > > I'm not sure what you mean by a stable vs a volatile inode number. Both NFS and CIFS (and SMB2) can return inode numbers or equivalent unique identifier, but in the case of CIFS some old servers don't support the calls which return inode numbers (or don't return them for all file system types, Windows FAT?) so in these cases cifs has to create inode numbers on the fly on the client. inode numbers created on the client are not "stable" they can change on unmount/remount (which can cause problems for backup applications). Similarly NFSv4 does not require that servers always return stable inode numbers (that will never change) and introduced a concept of "volatile file handle." We have run into this in two cases (there are probably more) - Specialized NFS servers for HPC which deal with lots of transient inodes, and second those for servers which base there inode number on path (Windows NFS?). See http://docs.oracle.com/cd/E19082-01/819-1634/rfsrefer-137/index.html or the NFSv4 RFC. Basically the question is whether it is worth reporting a flag on the call which returns the inode number to indicate that the inode number is "stable" (would not change on reboot or reconnection) or "volatile." Since the majority of NFS and SMB2 servers can return stable inode numbers, I don't feel strongly about the need for an indicator of "stable" vs. "volatile" but I mention it because backup and migration applications mention this (if inode numbers are volatile, they may have to check for hardlinks differently for example) >> > Should things like the Windows Archive, Hidden and System bits be handled >> > through IOC flags, perhaps expanded to 64-bits? >> >> Today I export these through an psuedo-xattr in cifs.ko, I am curious how >> NTFS and FAT export these on linux. > > NTFS: Not at all. > > FAT: The hidden bit causes the filename to get a dot prepended (and nothing > else is noted). > >> > Autofs, ntfs, btrfs, ... >> >> Given the overlap in optional attributes between the network >> protocol and local NTFS (and ReFS and to a lesser extent FAT) >> I would expect cifs.ko and the ntfs implementations >> info to map pretty closely. > > Yep. I wasn't going to do more filesystems till we'd finished arguing about > the basic arrangement of things in struct xstat. makes sense >> > Handle remote filesystems being offline and indicate this with >> > XSTAT_INFO_OFFLINE. >> >> You already have support for an indicator for offline files (HSM), > > HSM HSM is the more general case of two tiered data (disk vs. tape) en.wikipedia.org/wiki/Hierarchical_storage_management in the simplest case on "disk" (fast) vs. moved to tape (slow to retrieve) >> would XSTAT_INFO_OFFLINE be intended for the case >> where the network session to the server is disconnected >> (and in which you case the application does not want to reconnect)? > > Hmmm... Interesting question. Both NTFS and CIFS have an offline attribute > (which is where I originally got this from) - but should I have a separate > indicator to indicate the client can't access a server over a network > (ie. we've gone to disconnected operation on this file)? E.g. should there be > a XSTAT_INFO_DISCONNECTED too? my reaction is no, since it adds complexity. If you do a stat on a disconnected volume (where the network is temporarily down) reconnection will be attempted. If reconnection fails then the xstat will either fail or be retried forever depending on the value of "hard" vs. "soft" mount flag. -- Thanks, Steve -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
