In case anyone's curious here is my list of filesystems which I think should
have generic_file_checkpoint fops (31):
adfs
affs
befs
bfs
btrfs
cramfs
ecryptfs
efs
fat
freevxfs
hfs
hfsplus
hpfs
hppfs
isofs
jffs2
jfs
minix
ntfs
omfs
openpromfs
qnx4
ramfs
reiserfs
romfs
squashfs
sysv
ubifs
udf
ufs
xfs
I also added the checkpoint operation to generic_ro_fops since it's used
only in the set of filesystems listed above. For the curious:
befs
cramfs
efs
freevxfs
isofs
romfs
squashfs
I've got the patches split out per-filesystem even though they are
incredibly tiny. I'll keep rebasing them on the latest git trees from Dave's
kernel.org tree until the checkpoint fop set is ready to be sent to Oren.
The net result is I haven't added any checkpoint operations to filesystems
outside the lists above.
Open ramfs directories aren't checkpointable because, like many special
filesystems, the directories are kept in the dcache with
simple_dir_operations from libfs.c. Filesystems that use it include:
autofs
cifs
debugfs
devpts
fuse
hugetlbfs
ocfs2
ramfs
I think I could fix this with a private copy of simple_dir_operations but I
wasn't certain it would work or that it was the best way to handle it. So I've
postponed full ramfs checkpoint support. This means that ramfs files are always
checkpointable but the directories aren't.
A few "regular" filesystems have /proc or debugfs contents (many of them
using the seq_file API). These tend to contain information about the
filesystem or special control interfaces (btrfs). I'm not quite sure
what we'll want to do with these for now. I think eventually we'd add a
checkpoint operation to the seq_file API. My hunch is the majority
of seq_files won't be checkpointable. I also suspect that the
control files won't usually care what the file position is so we may be
able to add generic_file_checkpoint to those after a more careful review of
each one.
It may be easier to remember what's left "TODO" in fs/*:
9p
afs
autofs[4]
cifs
coda
configfs
debugfs
devpts
ext[234] (Dave's handling this)
(anything that uses dlm)
fuse
gfs2
hostfs
hugetlbfs
(anything that uses jbd[2])
ncpfs
nfs (I've got patches for NFS but I don't trust them yet and they lack
support for the seq_file interfaces in /proc)
ocfs2
proc (HUGE)
ramfs
smbfs (deprecated, so .. never?)
sysfs
bad_inode.c (unused outside bad_inode.c so low priority??)
binfmt_misc.c
block_dev.c
char_dev.c (def_chr_fops)
epoll (eventpoll.c)
eventfd.c
fifo.c
filesystems.c (/proc/filesystems)
no-block.c
notify/*
select.c
signalfd.c
locks.c
pipe.c
I haven't looked outside of fs/* for anything that uses struct file_operations
-- I'm assuming most of that is for "irregular" filesystems :).
Cheers,
-Matt
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