Something Else
vfs: kill write_super and sync_supers

Finally we can kill the 'sync_supers' kernel thread along with the
'->write_super()' superblock operation because all the users are gone.
Now every file-system is supposed to self-manage own superblock and
its dirty state.

The nice thing about killing this thread is that it improves power management.
Indeed, 'sync_supers' is a source of monotonic system wake-ups - it woke up
every 5 seconds no matter what - even if there were no dirty superblocks and
even if there were no file-systems using this service (e.g., btrfs and
journalled ext4 do not need it). So it was wasting power most of the time. And
because the thread was in the core of the kernel, all systems had to have it.
So I am quite happy to make it go away.

Interestingly, this thread is a left-over from the pdflush kernel thread which
was a self-forking kernel thread responsible for all the write-back in old
Linux kernels. It was turned into per-block device BDI threads, and
'sync_supers' was a left-over. Thus, R.I.P, pdflush as well.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
ext4: remove useless marking of superblock dirty

Commit a0375156 properly notes that superblock doesn't need to be marked
as dirty when only number of free inodes / blocks / number of directories
changes since that is recomputed on each mount anyway. However that comment
leaves some unnecessary markings as dirty in place. Remove these.

Artem: tested using xfstests for both journalled and non-journalled ext4.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Tested-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
ext4: convert last user of ext4_mark_super_dirty() to ext4_handle_dirty_super()

The last user of ext4_mark_super_dirty() in ext4_file_open() is so
rare it can well be modifying the superblock properly by journalling
the change.  Change it and get rid of ext4_mark_super_dirty() as it's
not needed anymore.

Artem: small amendments.
Artem: tested using xfstests for both journalled and non-journalled ext4.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Tested-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
ext4: remove unnecessary superblock dirtying

This patch changes the 'ext4_handle_dirty_super()' function which
submits the superblock for I/O in the following cases:

1. When creating the first large file on a file system without
   EXT4_FEATURE_RO_COMPAT_LARGE_FILE feature.
2. When re-sizing the file-system.
3. When creating an xattr on a file-system without the
   EXT4_FEATURE_COMPAT_EXT_ATTR feature.

If the file-system has journal enabled, the superblock is written via
the journal. We do not modify this path.

If the file-system has no journal, this function, falls back to just
marking the superblock as dirty using the 's_dirt' superblock
flag. This means that it delays the actual superblock I/O submission
by 5 seconds (default setting).  Namely, the 'sync_supers()' kernel
thread will call 'ext4_write_super()' later and will actually submit
the superblock for I/O.

And this is the behavior this patch modifies: we stop using 's_dirt'
and just mark the superblock buffer as dirty right away. Indeed, all 3
cases above are extremely rare and it does not add any value to delay
the I/O submission for them.

Note: 'ext4_handle_dirty_super()' executes
'__ext4_handle_dirty_super()' with 'now = 0'. This patch basically
makes the 'now' argument unneeded and it will be deleted in one of the
next patches.

This patch also removes 's_dirt' condition on the unmount path because
we never set it anymore, so we should not test it.

Tested using xfstests for both journalled and non-journalled ext4.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
ext4: weed out ext4_write_super

We do not depend on VFS's '->write_super()' anymore and do not need
the 's_dirt' flag anymore, so weed out 'ext4_write_super()' and
's_dirt'.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
ext4: nuke write_super from comments

The '->write_super' superblock method is gone, and this patch removes all the
references to 'write_super' from ext3.

Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
fat: introduce mark_fsinfo_dirty helper

A preparation patch which introduces a 'mark_fsinfo_dirty()' helper
function which just sets the 's_dirt' flag to 1 so far.  I'll add more
code to this helper later, so I do not mark it as 'inline'.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fat: mark superblock as dirty less often

Preparation for further changes.  It touches few functions in fatent.c and
prevents them from marking the superblock as dirty unnecessarily often.
Namely, instead of marking it as dirty in the internal tight loops - do it
only once at the end of the functions.  And instead of marking it as dirty
while holding the FAT table lock, do it outside the lock.

The reason for this patch is that marking the superblock as dirty will
soon become a little bit heavier operation, so it is cleaner to do this
only when it is necessary.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fat: introduce special inode for managing the FSINFO block

This is patchset makes fatfs stop using the VFS '->write_super()' method
for writing out the FSINFO block.

The final goal is to get rid of the 'sync_supers()' kernel thread.  This
kernel thread wakes up every 5 seconds (by default) and calls
'->write_super()' for all mounted file-systems.  And the bad thing is that
this is done even if all the superblocks are clean.  Moreover, some
file-systems do not even need this end they do not register the
'->write_super()' method at all (e.g., btrfs).

So 'sync_supers()' most often just generates useless wake-ups and wastes
power.  I am trying to make all file-systems independent of
'->write_super()' and plan to remove 'sync_supers()' and '->write_super'
completely once there are no more users.

The '->write_supers()' method is mostly used by baroque file-systems like
hfs, udf, etc.  Modern file-systems like btrfs and xfs do not use it.
This justifies removing this stuff from VFS completely and make every FS
self-manage own superblock.

Tested with xfstests.

This patch:

Preparation for further changes.  It introduces a special inode
('fsinfo_inode') in FAT file-system which we'll later use for managing the
FSINFO block.  Note, this there is already one special inode ('fat_inode')
which is used for managing the FAT tables.

Introduce new 'MSDOS_FSINFO_INO' constant for this special inode.  It is
safe to do because FAT file-system does not store inode numbers on the
media but generates them run-time.

I've also cleaned up the comment to existing 'MSDOS_ROOT_INO' constant,
while on it.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fat: switch to fsinfo_inode

Currently FAT file-system maps the VFS "superblock" abstraction to the
FSINFO block.  The FSINFO block contains non-essential data about the
amount of free clusters and the next free cluster.  FAT file-system can
always find out this information by scanning the FAT table, but having it
in the FSINFO block may speed things up sometimes.  So FAT file-system
relies on the VFS superblock write-out services to make sure the FSINFO
block is written out to the media from time to time.

The whole "superblock write-out" VFS infrastructure is served by the
'sync_supers()' kernel thread, which wakes up every 5 (by default) seconds
and writes out all dirty superblock using the '->write_super()' call-back.
 But the problem with this thread is that it wastes power by waking up the
system every 5 seconds no matter what.  So we want to kill it completely
and thus, we need to make file-systems to stop using the '->write_super'
VFS service, and then remove it together with the kernel thread.

This patch switches the FAT FSINFO block management from
'->write_super()'/'->s_dirt' to 'fsinfo_inode'/'->write_inode'.  Now,
instead of setting the 's_dirt' flag, we just mark the special
'fsinfo_inode' inode as dirty and let VFS invoke the '->write_inode'
call-back when needed, where we write-out the FSINFO block.

This patch also makes sure we do not mark the 'fsinfo_inode' inode as
dirty if we are not FAT32 (FAT16 and FAT12 do not have the FSINFO block)
or if we are in R/O mode.

As a bonus, we can also remove the '->sync_fs()' and '->write_super()' FAT
call-back function because they become unneeded.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
tmpfs: enable NOSEC optimization

Let tmpfs into the NOSEC optimization (avoiding file_remove_suid()
overhead on most common writes): set MS_NOSEC on its superblocks.

Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
tmpfs: optimize clearing when writing

Nick proposed years ago that tmpfs should avoid clearing its pages where
write will overwrite them with new data, as ramfs has long done.  But I
messed it up and just got bad data.  Tried again recently, it works
fine.

Here's time output for writing 4GiB 16 times on this Core i5 laptop:

before: real	0m21.169s user	0m0.028s sys	0m21.057s
        real	0m21.382s user	0m0.016s sys	0m21.289s
        real	0m21.311s user	0m0.020s sys	0m21.217s

after:  real	0m18.273s user	0m0.032s sys	0m18.165s
        real	0m18.354s user	0m0.020s sys	0m18.265s
        real	0m18.440s user	0m0.032s sys	0m18.337s

ramfs:  real	0m16.860s user	0m0.028s sys	0m16.765s
        real	0m17.382s user	0m0.040s sys	0m17.273s
        real	0m17.133s user	0m0.044s sys	0m17.021s

Yes, I have done perf reports, but they need more explanation than they
deserve: in summary, clear_page vanishes, its cache loading shifts into
copy_user_generic_unrolled; shmem_getpage_gfp goes down, and
surprisingly mark_page_accessed goes way up - I think because they are
respectively where the cache gets to be reloaded after being purged by
clear or copy.

Suggested-by: Nick Piggin <npiggin@gmail.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
tmpfs: support fallocate FALLOC_FL_PUNCH_HOLE

tmpfs has supported hole-punching since 2.6.16, via
madvise(,,MADV_REMOVE).

But nowadays fallocate(,FALLOC_FL_PUNCH_HOLE|FALLOC_FL_KEEP_SIZE,,) is
the agreed way to punch holes.

So add shmem_fallocate() to support that, and tweak shmem_truncate_range()
to support partial pages at both the beginning and end of range (never
needed for madvise, which demands rounded addr and rounds up length).

Based-on-patch-by: Cong Wang <amwang@redhat.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Cong Wang <amwang@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/fs: route MADV_REMOVE to FALLOC_FL_PUNCH_HOLE

Now tmpfs supports hole-punching via fallocate(), switch madvise_remove()
to use do_fallocate() instead of vmtruncate_range(): which extends
madvise(,,MADV_REMOVE) support from tmpfs to ext4, ocfs2 and xfs.

There is one more user of vmtruncate_range() in our tree,
staging/android's ashmem_shrink(): convert it to use do_fallocate() too
(but if its unpinned areas are already unmapped - I don't know - then it
would do better to use shmem_truncate_range() directly).

Based-on-patch-by: Cong Wang <amwang@redhat.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Colin Cross <ccross@android.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Greg Kroah-Hartman <gregkh@linux-foundation.org>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andreas Dilger <adilger@dilger.ca>
Cc: Mark Fasheh <mfasheh@suse.de>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Ben Myers <bpm@sgi.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/fs: remove truncate_range

Remove vmtruncate_range(), and remove the truncate_range method from
struct inode_operations: only tmpfs ever supported it, and tmpfs has now
converted over to using the fallocate method of file_operations.

Update Documentation accordingly, adding (setlease and) fallocate lines.
And while we're in mm.h, remove duplicate declarations of shmem_lock() and
shmem_file_setup(): everyone is now using the ones in shmem_fs.h.

Based-on-patch-by: Cong Wang <amwang@redhat.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Cong Wang <amwang@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fs: Tweak mount options for all partitions

Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
fs: default to noatime/nodiratime
Update sdcardfs