Nilfs object holds a back pointer to a writable super block instance
in nilfs->ns_writer, and this became eliminable since sb is now made
per device and all inodes have a valid pointer to it.

This deletes the ns_writer pointer and a reader/writer semaphore
protecting it.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

After applied the patch that unified sb instances, root dentry of
snapshots can be left in dcache even after their trees are unmounted.

The orphan root dentry/inode keeps a root object, and this causes
false positive of nilfs_checkpoint_is_mounted function.

This resolves the issue by having nilfs_checkpoint_is_mounted test
whether the root dentry is busy or not.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This makes use of iget5_locked to allocate or get inode for metadata
files to stop using own inode allocator.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This applies prepared rollback function and redirect function of
metadata file to DAT file, and eliminates GCDAT inode.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This stops pre-allocating nilfs object in nilfs_get_sb routine, and
stops managing its life cycle by reference counting.

nilfs_find_or_create_nilfs() function, nilfs->ns_mount_mutex,
nilfs_objects list, and the reference counter will be removed through
the simplification.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This stops allocating multiple super block instances for a device.

All snapshots and a current mode mount (i.e. latest tree) will be
controlled with nilfs_root objects that are kept within an sb
instance.

nilfs_get_sb() is rewritten so that it always has a root object for
the latest tree and snapshots make additional root objects.

The root dentry of the latest tree is binded to sb->s_root even if it
isn't attached on a directory.  Root dentries of snapshots or the
latest tree are binded to mnt->mnt_root on which they are mounted.

With this patch, nilfs_find_sbinfo() function, nilfs->ns_supers list,
and nilfs->ns_current back pointer, are deleted.  In addition,
init_nilfs() and load_nilfs() are simplified since they will be called
once for a device, not repeatedly called for mount points.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This rewrites nilfs_checkpoint_is_mounted() function so that it
decides whether a checkpoint is mounted by whether the corresponding
root object is found in checkpoint tree.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

To hold multiple versions of a filesystem in one sb instance, a new
on-memory structure is necessary to handle one or more checkpoints.

This adds a red-black tree of checkpoints to nilfs object, and adds
lookup and create functions for them.

Each checkpoint is represented by "nilfs_root" structure, and this
structure has rb_node to configure the rb-tree.

The nilfs_root object is identified with a checkpoint number.  For
each snapshot, a nilfs_root object is allocated and the checkpoint
number of snapshot is assigned to it.  For a regular mount
(i.e. current mode mount), NILFS_CPTREE_CURRENT_CNO constant is
assigned to the corresponding nilfs_root object.

Each nilfs_root object has an ifile inode and some counters.  These
items will displace those of nilfs_sb_info structure in successive
patches.
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>

Compatibility of nilfs partitions is now managed with three feature
sets.  This changes old compatibility check with revision number so
that it can accept future revisions.

Note that we can stop support of experimental versions of nilfs that
doesn't know the feature sets by incrementing NILFS_CURRENT_REV.  We
don't have to do it soon, but it would be a possible option whenever
the need arises.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

If load_nilfs() gets an error while doing recovery, it will fail to
free the shadow inode of dat (nilfs->ns_gc_dat).

This fixes the leak issue.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

nilfs_discard_segment() doesn't wait for completion of discard
requests.  This specifies BLKDEV_IFL_WAIT flag when calling
blkdev_issue_discard() in order to fix the sync failure.
Reported-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Cc: Christoph Hellwig <hch@lst.de>

After applying commit b2ac86e1, the following message got appeared
after unclean shutdown:

> NILFS warning: broken superblock. using spare superblock.

This turns out to be a false message due to the change which updates
two super blocks alternately.  The secondary super block now can be
selected if it's newer than the primary one.

This kills the false warning by suppressing it if another super block
is not actually broken.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This inserts sanity check that refuses to mount a filesystem with
unsupported block size.

Previously, kernel code of nilfs was looking only limitation of
devices though mkfs.nilfs2 limits the range of block sizes; there was
no check that prevents rec_len overflow with larger block sizes.

With this change, block sizes larger than 64KB or smaller than 1KB
will get rejected explicitly by kernel.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

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>

Super blocks of nilfs are periodically overwritten in order to record
the recent log position.  This shortens recovery time after unclean
unmount, but the current implementation performs the update even for a
few blocks of change.  If the filesystem gets small changes slowly and
continually, super blocks may be updated excessively.

This moderates the issue by skipping update of log cursor if it does
not cross a segment boundary.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

Although nilfs redundantly uses two super blocks and each may point to
different position on log, the current version of nilfs does not try
fallback to the spare super block when it doesn't find any valid log
at the position that the primary super block points to.

This has been a cause of mount failures due to write order reversals
on barrier less block devices.

This inserts fallback code in error path of nilfs_search_super_root
routine to resolve the mount failure problem.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This separates a setup routine of log cursor from init_nilfs().  The
routine, nilfs_store_log_cursor, reads the last position of the log
containing a super root, and initializes relevant state on the nilfs
object.
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 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>

This counter is unused.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

The function name of nilfs_recover_logical_segments makes no sense.
This changes the name into nilfs_salvage_orphan_logs to clarify the
role of the function.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

Most functions in recovery code take an argument of a super block
instance or a nilfs_sb_info struct for convenience sake.

This replaces them aggressively with a nilfs object by applying
__bread and __breadahead against routines using sb_bread and
sb_breadahead.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This stores blocksize in nilfs objects for the successive refactoring
of recovery logic.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

Nilfs maintains two super blocks, and selects the new one on mount
time if they both have valid checksums and their timestamps differ.

However, this has potential for mis-selection since the system clock
may be rewinded and the resolution of the timestamps is not high.

Usually this doesn't become an issue because both super blocks are
updated at the same time when the file system is unmounted.  Even if
the file system wasn't unmounted cleanly, the roll-forward recovery
will find the proper log which stores the latest super root.  Thus,
the issue can appear only if update of one super block fails and the
clock happens to be rewinded.

This fixes the issue by using checkpoint numbers instead of timestamps
to pick the super block storing the location of the latest log.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

After merging the block tree, today's linux-next build (powerpc ppc64_defconfig)
failed like this:

fs/nilfs2/the_nilfs.c: In function 'nilfs_discard_segments':
fs/nilfs2/the_nilfs.c:673: error: 'DISCARD_FL_BARRIER' undeclared (first use in this function)

Caused by commit fbd9b09a ("blkdev:
generalize flags for blkdev_issue_fn functions") interacting with commit
e902ec99 ("nilfs2: issue discard request
after cleaning segments") (which netered Linus' tree on about March 4 -
before v2.6.34-rc1).
Signed-off-by: NStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

This kills the following checkpatch warnings:

 WARNING: unnecessary whitespace before a quoted newline
 #869: FILE: super.c:869:
 +     	           "remount to a different snapshot. \n",

 WARNING: unnecessary whitespace before a quoted newline
 #389: FILE: the_nilfs.c:389:
 +     	    printk(KERN_ERR "NILFS: too short segment. \n");
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This adds a function to send discard requests for given array of
segment numbers, and calls the function when garbage collection
succeeded.
Signed-off-by: NJiro SEKIBA <jir@unicus.jp>
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This adds "norecovery" mount option which disables temporal write
access to read-only mounts or snapshots during mount/recovery.
Without this option, write access will be even performed for those
types of mounts; the temporal write access is needed to mount root
file system read-only after an unclean shutdown.

This option will be helpful when user wants to prevent any write
access to the device.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Cc: Eric Sandeen <sandeen@redhat.com>

This adds a helper function, nilfs_valid_fs() which returns if nilfs
is in a valid state or not.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

Although mount recovery of nilfs is integrated in load_nilfs()
procedure, the completion of recovery was isolated from the procedure
and performed at the end of the fill_super routine.

This was somewhat confusing since the recovery is needed for the nilfs
object, not for a super block instance.

To resolve the inconsistency, this will integrate the recovery
completion into load_nilfs().
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

Previously, this function took an status code to return possible error
codes.  The ("nilfs2: add local variable to cache the number of clean
segments") patch removed the possibility to return errors.

So, this simplifies the function definition to make it directly return
the number of clean segments.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This will hide a function call of nilfs_mdt_clear() in
nilfs_mdt_destroy().

This ensures nilfs_mdt_destroy() to do cleanup jobs included in
nilfs_mdt_clear().
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

Will displace nilfs_mdt_read_inode_direct function with an individual
read method: nilfs_dat_read, nilfs_sufile_read, nilfs_cpfile_read.

This provides the opportunity to initialize local variables of each
metadata file after reading the inode.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This will displace nilfs_mdt_new() constructor with individual
metadata file constructors like nilfs_dat_new(), new_sufile_new(),
nilfs_cpfile_new(), and nilfs_ifile_new().

This makes it possible for each metadata file to have own
intialization code.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This adds an optional "object size" argument to nilfs_mdt_new_common()
function; the argument specifies the size of private object attached
to a newly allocated metadata file inode.

This will afford space to keep local variables for meta data files.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

It has been unused since it was introduced in:

commit 520808bf20e90fdbdb320264ba7dd5cf9d47dcac
Author: Andrew Morton <akpm@osdl.org>
Date:   Fri May 21 00:46:17 2004 -0700

    [PATCH] block device layer: separate backing_dev_info infrastructure

So lets just kill it.
Acked-by: NJan Kara <jack@suse.cz>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

This gets rid of NILFS_CPFILE_GFP, NILFS_SUFILE_GFP, NILFS_DAT_GFP,
and NILFS_IFILE_GFP.  All of these constants refer to NILFS_MDT_GFP,
and can be removed.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

will get rid of nilfs_get_writer() and nilfs_put_writer() pair used to
retain a writable FS-instance for a period.

The pair functions were making up some kind of recursive lock with a
mutex, but they became overkill since the commit
201913ed.  Furthermore, they caused
the following lockdep warning because the mutex can be released by a
task which didn't lock it:

 =====================================
 [ BUG: bad unlock balance detected! ]
 -------------------------------------
 kswapd0/422 is trying to release lock (&nilfs->ns_writer_mutex) at:
 [<c1359ff5>] mutex_unlock+0x8/0xa
 but there are no more locks to release!

 other info that might help us debug this:
 no locks held by kswapd0/422.

 stack backtrace:
 Pid: 422, comm: kswapd0 Not tainted 2.6.31-rc4-nilfs #51
 Call Trace:
  [<c1358f97>] ? printk+0xf/0x18
  [<c104fea7>] print_unlock_inbalance_bug+0xcc/0xd7
  [<c11578de>] ? prop_put_global+0x3/0x35
  [<c1050195>] lock_release+0xed/0x1dc
  [<c1359ff5>] ? mutex_unlock+0x8/0xa
  [<c1359f83>] __mutex_unlock_slowpath+0xaf/0x119
  [<c1359ff5>] mutex_unlock+0x8/0xa
  [<d1284add>] nilfs_mdt_write_page+0xd8/0xe1 [nilfs2]
  [<c1092653>] shrink_page_list+0x379/0x68d
  [<c109171b>] ? isolate_pages_global+0xb4/0x18c
  [<c1092bd2>] shrink_list+0x26b/0x54b
  [<c10930be>] shrink_zone+0x20c/0x2a2
  [<c10936b7>] kswapd+0x407/0x591
  [<c1091667>] ? isolate_pages_global+0x0/0x18c
  [<c1040603>] ? autoremove_wake_function+0x0/0x33
  [<c10932b0>] ? kswapd+0x0/0x591
  [<c104033b>] kthread+0x69/0x6e
  [<c10402d2>] ? kthread+0x0/0x6e
  [<c1003e33>] kernel_thread_helper+0x7/0x1a

This patch uses a reader/writer semaphore instead of the own lock and
kills this warning.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This will remove every bd_mount_sem use in nilfs.

The intended exclusion control was replaced by the previous patch
("nilfs2: correct exclusion control in nilfs_remount function") for
nilfs_remount(), and this patch will replace remains with a new mutex
that this inserts in nilfs object.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>