mm: properly reflect task dirty limits in dirty_exceeded logic

We set bdi->dirty_exceeded (and thus ratelimiting code starts to
call balance_dirty_pages() every 8 pages) when a per-bdi limit is
exceeded or global limit is exceeded. But per-bdi limit also depends
on the task. Thus different tasks reach the limit on that bdi at
different levels of dirty pages. The result is that with current code
bdi->dirty_exceeded ping-ponged between 1 and 0 depending on which task
just got into balance_dirty_pages().

We fix the issue by clearing bdi->dirty_exceeded only when per-bdi amount
of dirty pages drops below the threshold (7/8 * bdi_dirty_limit) where task
limits already do not have any influence.

Impact:  The end result is, the dirty pages are kept more tightly under
control, with the average number slightly lowered than before.  This
reduces the risk to throttle light dirtiers and hence more responsive.
However it may add overheads by enforcing balance_dirty_pages() calls
on every 8 pages when there are 2+ heavy dirtiers.

CC: Andrew Morton <akpm@linux-foundation.org>
CC: Christoph Hellwig <hch@infradead.org>
CC: Dave Chinner <david@fromorbit.com>
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
(cherry picked from commit bcff25fc8aa47a13faff8b4b992589813f7b450a)
ext4: remove messy logic from ext4_ext_rm_leaf

- Both callers(truncate and punch_hole) already aligned left end point
  so we no longer need split logic here.
- Remove dead duplicated code.
- Call ext4_ext_dirty only after we have updated eh_entries, otherwise
  we'll loose entries update. Regression caused by d583fb87a3ff0
  266'th testcase in xfstests (http://patchwork.ozlabs.org/patch/120872)

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
(cherry picked from commit 750c9c47a5f9daa88333ac435a1afe4d4b428230)
ext4: update EOFBLOCKS flag on fallocate properly

EOFBLOCK_FL should be updated if called w/o FALLOCATE_FL_KEEP_SIZE
Currently it happens only if new extent was allocated.

TESTCASE:
fallocate test_file -n -l4096
fallocate test_file -l4096
Last fallocate cmd has updated size, but keept EOFBLOCK_FL set. And
fsck will complain about that.

Also remove ping pong in ext4_fallocate() in case of new extents,
where ext4_ext_map_blocks() clear EOFBLOCKS bit, and later
ext4_falloc_update_inode() restore it again.

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
(cherry picked from commit a4e5d88b1b24827f4f6a3cba43228936a67d81ba)
ext4: avoid setting directory i_nlink to zero

If a directory with more than EXT4_LINK_MAX subdirectories, the nlink
count is set to 1.  Subsequently, if any subdirectories are deleted,
ext4_dec_count() decrements the i_nlink count, which may go to 0
temporarily before being incremented back to 1.

While this is done under i_mutex, which prevents races for directory
and inode operations that check i_nlink, the temporary i_nlink == 0
case is exposed to userspace via stat() and similar calls that do not
hold i_mutex.

Instead, change the code to not decrement i_nlink count for any
directories that do not already have i_nlink larger than 2.

Reported-by: Cliff White <cliffw@whamcloud.com>
Reviewed-by: Johann Lombardi <johann@whamcloud.com>
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
(cherry picked from commit 909a4cf1ffe4b875c87abf38239a9bfd25167e0c)
ext4: use ext4_reserve_inode_write in ext4_xattr_set_handle

ext4_mark_iloc_dirty() says:

 * The caller must have previously called ext4_reserve_inode_write().
 * Give this, we know that the caller already has write access to iloc->bh.

ext4_xattr_set_handle, however, just open-codes it.  May as well use
the helper function for consistency.

No bug here, just tidiness.

(Note: on cleanup path, ext4_reserve_inode_write sets
the bh to NULL if it returns an error, and brelse() of
a null bh is handled gracefully).

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
(cherry picked from commit 665436175c3ca9d35f135e1ba6bdd63745cff08a)
ext4: error handling fix in ext4_ext_convert_to_initialized()

When allocated is unsigned it breaks the error handling at the end
of the function when we call:
	allocated = ext4_split_extent(...);
	if (allocated < 0)
		err = allocated;

I've made it a signed int instead of unsigned.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
(cherry picked from commit f85b287a01237857a50c93868231f7e831581a27)
ext4: handle NULL p_ext in ext4_ext_next_allocated_block()

In ext4_ext_next_allocated_block(), the path[depth] might
have a p_ext that is NULL -- see ext4_ext_binsearch().  In
such a case, dereferencing it will crash the machine.

This patch checks for p_ext == NULL in
ext4_ext_next_allocated_block() before dereferencinging it.

Tested using a hand-crafted an inode with eh_entries == 0 in
an extent block, verified that running FIEMAP on it crashes
without this patch, works fine with it.

Signed-off-by: Curt Wohlgemuth <curtw@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
(cherry picked from commit 6f8ff537266ee5396c920fb0c842a21df3055ff3)
ext4: let ext4_page_mkwrite stop started handle in failure

The started journal handle should be stopped in failure case.

Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Acked-by: Jan Kara <jack@suse.cz>
Cc: stable@kernel.org
(cherry picked from commit fcbb5515825f1bb20b7a6f75ec48bee61416f879)
ext4: use stream-alloc when mb_group_prealloc set to zero

The kernel will crash on

ext4_mb_mark_diskspace_used:
	BUG_ON(ac->ac_b_ex.fe_len <= 0);

after we set /sys/fs/ext4/sda/mb_group_prealloc to zero and create new files in an ext4 filesystem.

The reason is: ac_b_ex.fe_len also set to zero(mb_group_prealloc) in ext4_mb_normalize_group_request
because the ac_flags contains EXT4_MB_HINT_GROUP_ALLOC.

I think when someone set mb_group_prealloc to zero, it means DO NOT USE GROUP PREALLOCATION,
so we should set alloc-strategy to STREAM in this case.

Signed-off-by: Robin Dong <sanbai@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
(cherry picked from commit ebbe027797f67d34708ccfabdb129886d549f9ce)
ext4: remove unused variable in ext4_mb_generate_from_pa()

The variable 'count' in function ext4_mb_generate_from_pa() looks
useless, so remove it.

Signed-off-by: Robin Dong <sanbai@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
(cherry picked from commit 66a83cde47deb4e8874539326e12e88ed82158d3)
ext4: remove unused variable in mb_find_extent()

The variable 'ord' in function mb_find_extent() is redundant, so
remove it.

Signed-off-by: Robin Dong <sanbai@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
(cherry picked from commit b051d8dc4e1f011e1b0543a875f5861be5d90222)
ext4: fix a wrong comment in __mb_check_buddy()

The comment says the bit should be 0, but the after code assert the
bit to be 1.  This makes people confused, so fix it.

Signed-off-by: Robin Dong <sanbai@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
(cherry picked from commit 0a10da73e1fa6fb9b45f1166011ff3b04c27c010)
ext4: don't check io->flag when setting EXT4_STATE_DIO_UNWRITTEN inode state

When we want to convert the unitialized extent in direct write, we can
either do it in ext4_end_io_nolock(AIO case) or in
ext4_ext_direct_IO(non AIO case) and EXT4_I(inode)->cur_aio_dio is a
guard for ext4_ext_map_blocks to find the right case.  In e9e3bcecf,
we mistakenly change it by:

-			if (io)
+			if (io && !(io->flag & EXT4_IO_END_UNWRITTEN)) {
 				io->flag = EXT4_IO_END_UNWRITTEN;
-			else
+				atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten);
+			} else
 				ext4_set_inode_state(inode,
 						     EXT4_STATE_DIO_UNWRITTEN);

So now if we map 2 blocks, and the first one set the
EXT_IO_END_UNWRITTEN, the 2nd mapping will set inode state because of
the check for the flag. This is wrong.

Cc: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
(cherry picked from commit b3ff05690845911cc40387176f0bc5a7af9ef3ff)
ext4: optimize ext4_ext_convert_to_initialized()

This patch introduces a fast path in ext4_ext_convert_to_initialized()
for the case when the conversion can be performed by transferring
the newly initialized blocks from the uninitialized extent into
an adjacent initialized extent. Doing so removes the expensive
invocations of memmove() which occur during extent insertion and
the subsequent merge.

In practice this should be the common case for clients performing
append writes into files pre-allocated via
fallocate(FALLOC_FL_KEEP_SIZE). In such a workload performed via
direct IO and when using a suboptimal implementation of memmove()
(x86_64 prior to the 2.6.39 rewrite), this patch reduces kernel CPU
consumption by 32%.

Two new trace points are added to ext4_ext_convert_to_initialized()
to offer visibility into its operations. No exit trace point has
been added due to the multiplicity of return points. This can be
revisited once the upstream cleanup is backported.

Signed-off-by: Eric Gouriou <egouriou@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
(cherry picked from commit 6f91bc5fda82d2c49b4f7fb29424cf6a3c7574bc)
ext4: optimize memmmove lengths in extent/index insertions

ext4_ext_insert_extent() (respectively ext4_ext_insert_index())
was using EXT_MAX_EXTENT() (resp. EXT_MAX_INDEX()) to determine
how many entries needed to be moved beyond the insertion point.
In practice this means that (320 - I) * 24 bytes were memmove()'d
when I is the insertion point, rather than (#entries - I) * 24 bytes.

This patch uses EXT_LAST_EXTENT() (resp. EXT_LAST_INDEX()) instead
to only move existing entries. The code flow is also simplified
slightly to highlight similarities and reduce code duplication in
the insertion logic.

This patch reduces system CPU consumption by over 25% on a 4kB
synchronous append DIO write workload when used with the
pre-2.6.39 x86_64 memmove() implementation. With the much faster
2.6.39 memmove() implementation we still see a decrease in
system CPU usage between 2% and 7%.

Note that the ext_debug() output changes with this patch, splitting
some log information between entries. Users of the ext_debug() output
should note that the "move %d" units changed from reporting the number
of bytes moved to reporting the number of entries moved.

Signed-off-by: Eric Gouriou <egouriou@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
(cherry picked from commit 80e675f906db54eb1ce3a9555cee5f45b5b72ab2)

Conflicts:

	fs/ext4/extents.c