This one needs restarts...
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

need list_for_each_entry_safe() here.  Original didn't even
have restart logics, so if you race with umount() it blew up.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

At the same time we can kill s_need_restart and local mutex in there.
__put_super() made public for a while; will be gone later.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

We used to remove from s_list and s_instances at the same
time.  So let's *not* do the former and skip superblocks
that have empty s_instances in the loops over s_list.

The next step, of course, will be to get rid of rescan logics
in those loops.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Make sure that s_umount is acquired *before* we drop the final
active reference; we still have the fast path (atomic_dec_unless)
and we have gotten rid of the window between the moment when
s_active hits zero and s_umount is acquired.  Which simplifies
the living hell out of grab_super() and inotify pin_to_kill()
stuff.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

use atomic_inc_not_zero(&sb->s_active) instead of playing games with
checking ->s_count > S_BIAS
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

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

When CONFIG_BLOCK is set, it ends up getting backing-dev.h included.
But for !CONFIG_BLOCK, it isn't so lucky. The proper thing to do is
include <linux/backing-dev.h> directly from the file it's used from,
so do that.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

noop_backing_dev_info is used only as a flag to mark filesystems that
don't have any backing store, like tmpfs, procfs, spufs, etc.
Signed-off-by: NJoern Engel <joern@logfs.org>

Changed the BUG_ON() to a WARN_ON(). Note that adding dirty inodes
to the noop_backing_dev_info is not legal and will not result in
them being flushed, but we already catch this condition in
__mark_inode_dirty() when checking for a registered bdi.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Invalidate sb->s_bdev on remount,ro.

Fixes a problem reported by Jorge Boncompte who is seeing corruption
trying to snapshot a minix filesystem image.  Some filesystems modify
their metadata via a path other than the bdev buffer cache (eg.  they may
use a private linear mapping for their metadata, or implement directories
in pagecache, etc).  Also, file data modifications usually go to the bdev
via their own mappings.

These updates are not coherent with buffercache IO (eg.  via /dev/bdev)
and never have been.  However there could be a reasonable expectation that
after a mount -oremount,ro operation then the buffercache should
subsequently be coherent with previous filesystem modifications.

So invalidate the bdev mappings on a remount,ro operation to provide a
coherency point.

The problem was exposed when we switched the old rd to brd because old rd
didn't really function like a normal block device and updates to rd via
mappings other than the buffercache would still end up going into its
buffercache.  But the same problem has always affected other "normal"
block devices, including loop.

[akpm@linux-foundation.org: repair comment layout]
Reported-by: N"Jorge Boncompte [DTI2]" <jorge@dti2.net>
Tested-by: N"Jorge Boncompte [DTI2]" <jorge@dti2.net>
Signed-off-by: NNick Piggin <npiggin@suse.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Filesystem code usually destroys the option buffer while
parsing it. This leads to errors when the same buffer is
passed twice. In case we fill a new superblock do not call
remount.

This is needed to quite a warning that the debugfs code
causes every boot.

Cc: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NKay Sievers <kay.sievers@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Currently we held s_umount while a filesystem is frozen, despite that we
might return to userspace and unlock it from a different process.  Instead
grab an active reference to keep the file system busy and add an explicit
check for frozen filesystems in remount and reject the remount instead
of blocking on s_umount.

Add a new get_active_super helper to super.c for use by freeze_bdev that
grabs an active reference to a superblock from a given block device.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Now that we have the freeze count there is not much reason for bd_mount_sem
anymore.  The actual freeze/thaw operations are serialized using the
bd_fsfreeze_mutex, and the only other place we take bd_mount_sem is
get_sb_bdev which tries to prevent mounting a filesystem while the block
device is frozen.  Instead of add a check for bd_fsfreeze_count and
return -EBUSY if a filesystem is frozen.  While that is a change in user
visible behaviour a failing mount is much better for this case rather
than having the mount process stuck uninterruptible for a long time.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

sb->s_maxbytes is supposed to indicate the maximum size of a file that can
exist on the filesystem.  It's declared as an unsigned long long.

Even if a filesystem has no inherent limit that prevents it from using
every bit in that unsigned long long, it's still problematic to set it to
anything larger than MAX_LFS_FILESIZE.  There are places in the kernel
that cast s_maxbytes to a signed value.  If it's set too large then this
cast makes it a negative number and generally breaks the comparison.

Change s_maxbytes to be loff_t instead.  That should help eliminate the
temptation to set it too large by making it a signed value.

Also, add a warning for couple of releases to help catch filesystems that
set s_maxbytes too large.  Eventually we can either convert this to a
BUG() or just remove it and in the hope that no one will get it wrong now
that it's a signed value.
Signed-off-by: NJeff Layton <jlayton@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Robert Love <rlove@google.com>
Cc: Mandeep Singh Baines <msb@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

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>

We do this automatically in get_sb_bdev() from the set_bdev_super()
callback. Filesystems that have their own private backing_dev_info
must assign that in ->fill_super().

Note that ->s_bdi assignment is required for proper writeback!
Acked-by: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

This gets rid of pdflush for bdi writeout and kupdated style cleaning.
pdflush writeout suffers from lack of locality and also requires more
threads to handle the same workload, since it has to work in a
non-blocking fashion against each queue. This also introduces lumpy
behaviour and potential request starvation, since pdflush can be starved
for queue access if others are accessing it. A sample ffsb workload that
does random writes to files is about 8% faster here on a simple SATA drive
during the benchmark phase. File layout also seems a LOT more smooth in
vmstat:

 r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy id wa
 0  1      0 608848   2652 375372    0    0     0 71024  604    24  1 10 48 42
 0  1      0 549644   2712 433736    0    0     0 60692  505    27  1  8 48 44
 1  0      0 476928   2784 505192    0    0     4 29540  553    24  0  9 53 37
 0  1      0 457972   2808 524008    0    0     0 54876  331    16  0  4 38 58
 0  1      0 366128   2928 614284    0    0     4 92168  710    58  0 13 53 34
 0  1      0 295092   3000 684140    0    0     0 62924  572    23  0  9 53 37
 0  1      0 236592   3064 741704    0    0     4 58256  523    17  0  8 48 44
 0  1      0 165608   3132 811464    0    0     0 57460  560    21  0  8 54 38
 0  1      0 102952   3200 873164    0    0     4 74748  540    29  1 10 48 41
 0  1      0  48604   3252 926472    0    0     0 53248  469    29  0  7 47 45

where vanilla tends to fluctuate a lot in the creation phase:

 r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy id wa
 1  1      0 678716   5792 303380    0    0     0 74064  565    50  1 11 52 36
 1  0      0 662488   5864 319396    0    0     4   352  302   329  0  2 47 51
 0  1      0 599312   5924 381468    0    0     0 78164  516    55  0  9 51 40
 0  1      0 519952   6008 459516    0    0     4 78156  622    56  1 11 52 37
 1  1      0 436640   6092 541632    0    0     0 82244  622    54  0 11 48 41
 0  1      0 436640   6092 541660    0    0     0     8  152    39  0  0 51 49
 0  1      0 332224   6200 644252    0    0     4 102800  728    46  1 13 49 36
 1  0      0 274492   6260 701056    0    0     4 12328  459    49  0  7 50 43
 0  1      0 211220   6324 763356    0    0     0 106940  515    37  1 10 51 39
 1  0      0 160412   6376 813468    0    0     0  8224  415    43  0  6 49 45
 1  1      0  85980   6452 886556    0    0     4 113516  575    39  1 11 54 34
 0  2      0  85968   6452 886620    0    0     0  1640  158   211  0  0 46 54

A 10 disk test with btrfs performs 26% faster with per-bdi flushing. A
SSD based writeback test on XFS performs over 20% better as well, with
the throughput being very stable around 1GB/sec, where pdflush only
manages 750MB/sec and fluctuates wildly while doing so. Random buffered
writes to many files behave a lot better as well, as does random mmap'ed
writes.

A separate thread is added to sync the super blocks. In the long term,
adding sync_supers_bdi() functionality could get rid of this thread again.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

This is a first step at introducing per-bdi flusher threads. We should
have no change in behaviour, although sb_has_dirty_inodes() is now
ridiculously expensive, as there's no easy way to answer that question.
Not a huge problem, since it'll be deleted in subsequent patches.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Standard trick - add a new variable (start) such that
for each n < start n is known to be busy.  Allocation can
skip checking everything in [0..start) and if it returns
n, we can set start to n + 1.  Freeing below start sets
start to what we'd just freed.

Of course, it still sucks if we do something like
	free 0
	allocate
	allocate
in a loop - still O(n^2) time.  However, on saner loads it
improves the things a lot and the entire thing is not worth
the trouble of switching to something with better worst-case
behaviour.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

commit 337eb00a
Push BKL down into ->remount_fs()
and
commit 4aa98cf7
Push BKL down into do_remount_sb()

were uncorrectly merged.
The former removes one pair of lock/unlock_kernel(), but the latter adds
several unlock_kernel(). Finally a few unlock_kernel() calls left.
Signed-off-by: NJ. R. Okajima <hooanon05@yahoo.co.jp>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

[xfs, btrfs, capifs, shmem don't need BKL, exempt]
Signed-off-by: NAlessio Igor Bogani <abogani@texware.it>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Push down lock_super into ->write_super instances and remove it from the
caller.

Following filesystem don't need ->s_lock in ->write_super and are skipped:

 * bfs, nilfs2 - no other uses of s_lock and have internal locks in
	->write_super
 * ext2 - uses BKL in ext2_write_super and has internal calls without s_lock
 * reiserfs - no other uses of s_lock as has reiserfs_write_lock (BKL) in
 	->write_super
 * xfs - no other uses of s_lock and uses internal lock (buffer lock on
	superblock buffer) to serialize ->write_super.  Also xfs_fs_write_super
	is superflous and will go away in the next merge window
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

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

Note that since we can't run into contention between remount_fs and write_super
(due to exclusion on s_umount), we have to care only about filesystems that
touch lock_super() on their own.  Out of those ext3, ext4, hpfs, sysv and ufs
do need it; fat doesn't since its ->remount_fs() only accesses assign-once
data (basically, it's "we have no atime on directories and only have atime on
files for vfat; force nodiratime and possibly noatime into *flags").

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

Move BKL into ->put_super from the only caller.  A couple of
filesystems had trivial enough ->put_super (only kfree and NULLing of
s_fs_info + stuff in there) to not get any locking: coda, cramfs, efs,
hugetlbfs, omfs, qnx4, shmem, all others got the full treatment.  Most
of them probably don't need it, but I'd rather sort that out individually.
Preferably after all the other BKL pushdowns in that area.

[AV: original used to move lock_super() down as well; these changes are
removed since we don't do lock_super() at all in generic_shutdown_super()
now]
[AV: fuse, btrfs and xfs are known to need no damn BKL, exempt]
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

We can't run into contention on it.  All other callers of lock_super()
either hold s_umount (and we have it exclusive) or hold an active
reference to superblock in question, which prevents the call of
generic_shutdown_super() while the reference is held.  So we can
replace lock_super(s) with get_fs_excl() in generic_shutdown_super()
(and corresponding change for unlock_super(), of course).

Since ext4 expects s_lock held for its put_super, take lock_super()
into it.  The rest of filesystems do not care at all.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Merge the write_super helper into sync_super and move the check for
->write_super earlier so that we can avoid grabbing a reference to
a superblock that doesn't have it.

While we're at it also add a little comment documenting sync_supers.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

We just did a full fs writeout using sync_filesystem before, and if
that's not enough for the filesystem it can perform it's own writeout
in ->put_super, which many filesystems already do.

Move a call to foofs_write_super into every foofs_put_super for now to
guarantee identical behaviour until it's cleaned up by the individual
filesystem maintainers.

Exceptions:

 - affs already has identical copy & pasted code at the beginning of
   affs_put_super so no need to do it twice.
 - xfs does the right thing without it and I have changes pending for
   the xfs tree touching this are so I don't really need conflicts
   here..
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Rename the function so that it better describe what it really does. Also
remove the unnecessary include of buffer_head.h.
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Move sync_filesystems(), __fsync_super(), fsync_super() from
super.c to sync.c where it fits better.

[build fixes folded]
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

It is unnecessarily fragile to have two places (fsync_super() and do_sync())
doing data integrity sync of the filesystem. Alter __fsync_super() to
accommodate needs of both callers and use it. So after this patch
__fsync_super() is the only place where we gather all the calls needed to
properly send all data on a filesystem to disk.

Nice bonus is that we get a complete livelock avoidance and write_supers()
is now only used for periodic writeback of superblocks.

sync_blockdevs() introduced a couple of patches ago is gone now.

[build fixes folded]
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

__fsync_super() does the same thing as fsync_super(). So change the only
caller to use fsync_super() and make __fsync_super() static. This removes
unnecessarily duplicated call to sync_blockdev() and prepares ground
for the changes to __fsync_super() in the following patches.
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

sync_filesystems() has a condition that if wait == 0 and s_dirt == 0, then
->sync_fs() isn't called. This does not really make much sence since s_dirt is
generally used by a filesystem to mean that ->write_super() needs to be called.
But ->sync_fs() does different things. I even suspect that some filesystems
(btrfs?) sets s_dirt just to fool this logic.
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

So far, do_sync() called:
  sync_inodes(0);
  sync_supers();
  sync_filesystems(0);
  sync_filesystems(1);
  sync_inodes(1);

This ordering makes it kind of hard for filesystems as sync_inodes(0) need not
submit all the IO (for example it skips inodes with I_SYNC set) so e.g. forcing
transaction to disk in ->sync_fs() is not really enough. Therefore sys_sync has
not been completely reliable on some filesystems (ext3, ext4, reiserfs, ocfs2
and others are hit by this) when racing e.g. with background writeback. A
similar problem hits also other filesystems (e.g. ext2) because of
write_supers() being called before the sync_inodes(1).

Change the ordering of calls in do_sync() - this requires a new function
sync_blockdevs() to preserve the property that block devices are always synced
after write_super() / sync_fs() call.

The same issue is fixed in __fsync_super() function used on umount /
remount read-only.

[AV: build fixes]
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Remove the unused s_async_list in the superblock, a leftover of the
broken async inode deletion code that leaked into mainline.  Having this
in the middle of the sync/unmount path is not helpful for the following
cleanups.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>