The previous export operations cannot handle multiple versions of
a filesystem if they belong to the same sb instance.

This adds a new type of file handle and extends export operations so
that they can get the inode specified by a checkpoint number as well
as an inode number and a generation number.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This puts a pointer to nilfs_root object in the private part of
on-memory inode, and makes nilfs_iget function pick up the inode with
the same root object.

Non-root inodes inherit its nilfs_root object from parent inode.  That
of the root inode is allocated through nilfs_attach_checkpoint()
function.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This uses inode hash function that vfs provides instead of the own
hash table for caching gc inodes.  This finally removes the own inode
hash from nilfs.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

[folded build fix from sfr]
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

This forces nilfs to check compatibility of feature flags so as to
reject a filesystem with unknown features when it mounts or remounts
the filesystem.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This removes nilfs_bmap_union and finally unifies three structures and
the union in bmap/btree code into one.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This will sync super blocks in turns instead of syncing duplicate
super blocks at the time.  This will help searching valid super root
when super block is written into disk before log is written, which is
happen when barrier-less block devices are unmounted uncleanly.  In
the situation, old super block likely points to valid log.

This patch introduces ns_sbwcount member to the nilfs object and adds
nilfs_sb_will_flip() function; ns_sbwcount counts how many times super
blocks write back to the disk.  And, nilfs_sb_will_flip() decides
whether flipping required or not based on the count of ns_sbwcount to
sync super blocks asymmetrically.

The following functions are also changed:

 - nilfs_prepare_super(): flips super blocks according to the
   argument.  The argument is calculated by nilfs_sb_will_flip()
   function.

 - nilfs_cleanup_super(): sets "clean" flag to both super blocks if
   they point to the same checkpoint.

To update both of super block information, caller of
nilfs_commit_super must set the information on both super blocks.
Signed-off-by: NJiro SEKIBA <jir@unicus.jp>
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This function checks validity of super block pointers.
If first super block is invalid, it will swap the super blocks.
The function should be called before any super block information updates.
Caller must obtain nilfs->ns_sem.
Signed-off-by: NJiro SEKIBA <jir@unicus.jp>
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This moves out section that updates information of the recent log
position stored in super blocks from nilfs_commit_super to a new
routine named nilfs_set_log_cursor.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This function write out filesystem state to super blocks in order to
share the same cleanup work.  This is a preparation for making super
block writeback alternately.

Cc: Jiro SEKIBA <jir@unicus.jp>
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

... especially when it only needs (and initializes) .d_name of it
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

[akpm@linux-foundation.org: fix KVM]
Signed-off-by: NAlexey Dobriyan <adobriyan@gmail.com>
Acked-by: NMike Frysinger <vapier@gentoo.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NAlexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NAlexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Actually, get rid of private analog, since nothing in there is
using ACLs at all so far.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Previously, default_backing_dev_info was used for the mapping of btree
node caches.  This uses device dependent backing_dev_info to allow
detailed control of the device for the btree node pages.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This is a companion patch to ("nilfs2: fix possible circular locking
for get information ioctls").

This corrects lock order reversal between mm->mmap_sem and
nilfs->ns_segctor_sem in nilfs_clean_segments() which was detected by
lockdep check:

 =======================================================
 [ INFO: possible circular locking dependency detected ]
 2.6.30-rc3-nilfs-00003-g360bdc1 #7
 -------------------------------------------------------
 mmap/5294 is trying to acquire lock:
  (&nilfs->ns_segctor_sem){++++.+}, at: [<d0d0e846>] nilfs_transaction_begin+0xb6/0x10c [nilfs2]

 but task is already holding lock:
  (&mm->mmap_sem){++++++}, at: [<c043700a>] do_page_fault+0x1d8/0x30a

 which lock already depends on the new lock.

 the existing dependency chain (in reverse order) is:

 -> #1 (&mm->mmap_sem){++++++}:
        [<c01470a5>] __lock_acquire+0x1066/0x13b0
        [<c01474a9>] lock_acquire+0xba/0xdd
        [<c01836bc>] might_fault+0x68/0x88
        [<c023c61d>] copy_from_user+0x2a/0x111
        [<d0d120d0>] nilfs_ioctl_prepare_clean_segments+0x1d/0xf1 [nilfs2]
        [<d0d0e2aa>] nilfs_clean_segments+0x6d/0x1b9 [nilfs2]
        [<d0d11f68>] nilfs_ioctl+0x2ad/0x318 [nilfs2]
        [<c01a3be7>] vfs_ioctl+0x22/0x69
        [<c01a408e>] do_vfs_ioctl+0x460/0x499
        [<c01a4107>] sys_ioctl+0x40/0x5a
        [<c01031a4>] sysenter_do_call+0x12/0x38
        [<ffffffff>] 0xffffffff

 -> #0 (&nilfs->ns_segctor_sem){++++.+}:
        [<c0146e0b>] __lock_acquire+0xdcc/0x13b0
        [<c01474a9>] lock_acquire+0xba/0xdd
        [<c0433f1d>] down_read+0x2a/0x3e
        [<d0d0e846>] nilfs_transaction_begin+0xb6/0x10c [nilfs2]
        [<d0cfe0e5>] nilfs_page_mkwrite+0xe7/0x154 [nilfs2]
        [<c0183b0b>] __do_fault+0x165/0x376
        [<c01855cd>] handle_mm_fault+0x287/0x5d1
        [<c043712d>] do_page_fault+0x2fb/0x30a
        [<c0435462>] error_code+0x72/0x78
        [<ffffffff>] 0xffffffff

where nilfs_clean_segments() holds:

  nilfs->ns_segctor_sem -> copy_from_user()
                             --> page fault -> mm->mmap_sem

And, page fault path may hold:

  page fault -> mm->mmap_sem
         --> nilfs_page_mkwrite() -> nilfs->ns_segctor_sem

Even though nilfs_clean_segments() does not perform write access on
given user pages, it may cause deadlock because nilfs->ns_segctor_sem
is shared per device and mm->mmap_sem can be shared with other tasks.

To avoid this problem, this patch moves all calls of copy_from_user()
outside the nilfs->ns_segctor_sem lock in the ioctl.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

A MODULE_VERSION() macro has been used in out-of-tree nilfs modules,
but it's needless and not updated in tree.  So, this removes it along
with the version declaration.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

After a review of user's feedback for finding out other compatibility
issues, I found nilfs improperly initializes timestamps in inode;
CURRENT_TIME was used there instead of CURRENT_TIME_SEC even though nilfs
didn't have nanosecond timestamps on disk.  A few users gave us the report
that the tar program sometimes failed to expand symbolic links on nilfs,
and it turned out to be the cause.

Instead of applying the above displacement, I've decided to support
nanosecond timestamps on this occation.  Fortunetaly, a needless 64-bit
field was in the nilfs_inode struct, and I found it's available for this
purpose without impact for the users.

So, this will do the enhancement and resolve the tar problem.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The former versions didn't have extra super blocks.  This improves the
weak point by introducing another super block at unused region in tail of
the partition.

This doesn't break disk format compatibility; older versions just ingore
the secondary super block, and new versions just recover it if it doesn't
exist.  The partition created by an old mkfs may not have unused region,
but in that case, the secondary super block will not be added.

This doesn't make more redundant copies of the super block; it is a future
work.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Pekka Enberg advised me:
> It would be nice if BUG(), BUG_ON(), and panic() calls would be
> converted to proper error handling using WARN_ON() calls. The BUG()
> call in nilfs_cpfile_delete_checkpoints(), for example, looks to be
> triggerable from user-space via the ioctl() system call.

This will follow the comment and keep them to a minimum.
Acked-by: NPekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Pekka Enberg suggested converting ->ioctl operations to use
->unlocked_ioctl to avoid BKL.

The conversion was verified to be safe, so I will take it on this
occasion.

Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This removes compat code from the nilfs ioctls and applies the same
function for both .ioctl and .compat_ioctl file operations.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Pekka Enberg pointed out that double error handlings found after
nilfs_transaction_end() can be avoided by separating abort operation:

 OK, I don't understand this. The only way nilfs_transaction_end() can
 fail is if we have NILFS_TI_SYNC set and we fail to construct the
 segment. But why do we want to construct a segment if we don't commit?

 I guess what I'm asking is why don't we have a separate
 nilfs_transaction_abort() function that can't fail for the erroneous
 case to avoid this double error value tracking thing?

This does the separation and renames nilfs_transaction_end() to
nilfs_transaction_commit() for clarification.

Since, some calls of these functions were used just for exclusion control
against the segment constructor, they are replaced with semaphore
operations.
Acked-by: NPekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This adds the following common structures of the NILFS2 file system.

* nilfs_inode_info structure:
  gives on-memory inode.

* nilfs_sb_info structure:
  keeps per-mount state and a special inode for the ifile.
  This structure is attached to the super_block structure.

* the_nilfs structure:
  keeps shared state and locks among a read/write mount and snapshot
  mounts.  This keeps special inodes for the sufile, cpfile, dat, and
  another dat inode used during GC (gcdat).  This also has a hash table
  of dummy inodes to cache disk blocks during GC (gcinodes).

* nilfs_transaction_info structure:
  keeps per task state while nilfs is writing logs or doing indivisible
  inode or namespace operations.  This structure is used to identify
  context during log making and store nest level of the lock which
  ensures atomicity of file system operations.
Signed-off-by: NKoji Sato <sato.koji@lab.ntt.co.jp>
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>