Currently, there exists a race between delayed allocated writes and
the writeback when bigalloc feature is in use. The race was because we
wanted to determine what blocks in a cluster are under delayed
allocation and we were using buffer_delayed(bh) check for it. But, the
writeback codepath clears this bit without any synchronization which
resulted in a race and an ext4 warning similar to:

EXT4-fs (ram1): ext4_da_update_reserve_space: ino 13, used 1 with only 0
		reserved data blocks

The race existed in two places.
(1) between ext4_find_delalloc_range() and ext4_map_blocks() when called from
    writeback code path.
(2) between ext4_find_delalloc_range() and ext4_da_get_block_prep() (where
    buffer_delayed(bh) is set.

To fix (1), this patch introduces a new buffer_head state bit -
BH_Da_Mapped.  This bit is set under the protection of
EXT4_I(inode)->i_data_sem when we have actually mapped the delayed
allocated blocks during the writeout time. We can now reliably check
for this bit inside ext4_find_delalloc_range() to determine whether
the reservation for the blocks have already been claimed or not.

To fix (2), it was necessary to set buffer_delay(bh) under the
protection of i_data_sem.  So, I extracted the very beginning of
ext4_map_blocks into a new function - ext4_da_map_blocks() - and
performed the required setting of bh_delay bit and the quota
reservation under the protection of i_data_sem.  These two fixes makes
the checking of buffer_delay(bh) and buffer_da_mapped(bh) consistent,
thus removing the race.

Tested: I was able to reproduce the problem by running 'dd' and
'fsync' in parallel. Also, xfstests sometimes used to reproduce this
race. After the fix both my test and xfstests were successful and no
race (warning message) was observed.

Google-Bug-Id: 4997027
Signed-off-by: NAditya Kali <adityakali@google.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

This patch adds some tracepoints in ext4/extents.c and updates a tracepoint in
ext4/inode.c.

Tested: Built and ran the kernel and verified that these tracepoints work.
Also ran xfstests.
Signed-off-by: NAditya Kali <adityakali@google.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>
    

With bigalloc changes, the i_blocks value was not correctly set (it was still
set to number of blocks being used, but in case of bigalloc, we want i_blocks
to represent the number of clusters being used). Since the quota subsystem sets
the i_blocks value, this patch fixes the quota accounting and makes sure that
the i_blocks value is set correctly.
Signed-off-by: NAditya Kali <adityakali@google.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

When we are truncating (as opposed unlinking) a file, we need to worry
about partial truncates of a file, especially in the light of sparse
files.  The changes here make sure that arbitrary truncates of sparse
files works correctly.  Yeah, it's messy.

Note that these functions will need to be revisted when the punch
ioctl is integrated --- in fact this commit will probably have merge
conflicts with the punch changes which Allison Henders and the IBM LTC
have been working on.  I will need to fix this up when either patch
hits mainline.
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

If we need to allocate a new block in ext4_ext_map_blocks(), the
function needs to see if the cluster has already been allocated.
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

While running extended fsx tests to verify the first
two patches, a similar bug was also found in the
truncate operation.

This bug happens because the truncate routine only zeros
the unblock aligned portion of the last page.  This means
that the block aligned portions of the page appearing after
i_size are left unzeroed, and the buffer heads still mapped.

This bug is corrected by using ext4_discard_partial_page_buffers
in the truncate routine to zero the partial page and unmap
the buffer headers.
Signed-off-by: NAllison Henderson <achender@linux.vnet.ibm.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

Add debugging information in case jbd2_journal_dirty_metadata() is
called with a buffer_head which didn't have
jbd2_journal_get_write_access() called on it, or if the journal_head
has the wrong transaction in it.  In addition, return an error code.
This won't change anything for ocfs2, which will BUG_ON() the non-zero
exit code.

For ext4, the caller of this function is ext4_handle_dirty_metadata(),
and on seeing a non-zero return code, will call __ext4_journal_stop(),
which will print the function and line number of the (buggy) calling
function and abort the journal.  This will allow us to recover instead
of bug halting, which is better from a robustness and reliability
point of view.
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

This patch fixes a second punch hole bug found by xfstests 127.

This bug happens because punch hole needs to flush the pages
of the hole to avoid race conditions.  But if the end of the
hole is in the same page as i_size, the buffer heads beyond
i_size need to be unmapped and the page needs to be zeroed
after it is flushed.

To correct this, the new ext4_discard_partial_page_buffers
routine is used to zero and unmap the partial page
beyond i_size if the end of the hole appears in the same
page as i_size.

The code has also been optimized to set the end of the hole
to the page after i_size if the specified hole exceeds i_size,
and the code that flushes the pages has been simplified.
Signed-off-by: NAllison Henderson <achender@linux.vnet.ibm.com>

This patch addresses a bug found by xfstests 75, 112, 127
when blocksize = 1k

This bug happens because the punch hole code only zeros
out non block aligned regions of the page.  This means that if the
blocks are smaller than a page, then the block aligned regions of
the page inside the hole are left un-zeroed, and their buffer heads
are still mapped.  This bug is corrected by using
ext4_discard_partial_page_buffers to properly zero the partial page
at the head and tail of the hole, and unmap the corresponding buffer
heads

This patch also addresses a bug reported by Lukas while working on a
new patch to add discard support for loop devices using punch hole.
The bug happened because of the first and last block number
needed to be cast to a larger data type before calculating the
byte offset, but since now we only need the byte offsets of the
pages, we no longer even need to be calculating the byte offsets
of the blocks.  The code to do the block offset calculations is
removed in this patch.
Signed-off-by: NAllison Henderson <achender@linux.vnet.ibm.com>

The logical block number in map.l_blk is a __u32, and so before we
shift it left, by the block size, we neeed cast it to a 64-bit size.

Otherwise i_size can be corrupted on an ENOSPC.

# df -T /mnt/mp1
Filesystem    Type   1K-blocks      Used Available Use% Mounted on
/dev/sda6     ext4     9843276    153056   9190200   2% /mnt/mp1
# fallocate -o 0 -l 2199023251456 /mnt/mp1/testfile
fallocate: /mnt/mp1/testfile: fallocate failed: No space left on device
# stat /mnt/mp1/testfile
  File: `/mnt/mp1/testfile'
  Size: 4293656576	Blocks: 19380440   IO Block: 4096   regular file
Device: 806h/2054d	Inode: 12          Links: 1
Access: (0644/-rw-r--r--)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2011-07-25 13:01:31.414490496 +0900
Modify: 2011-07-25 13:01:31.414490496 +0900
Change: 2011-07-25 13:01:31.454490495 +0900
Signed-off-by: NUtako Kusaka <u-kusaka@wm.jp.nec.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>
--
 fs/ext4/extents.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

The old function ext4_ext_rm_idx is used only for truncate case
because it just remove last index in extent-index-block. When punching
hole, it usually needed to remove "middle" index, therefore we must
move indexes which after it forward.

(I create a file with 1 depth extent tree and punch hole in the middle
of it, the last index in index-block strangly gone, so I find out this
bug)
Signed-off-by: NRobin Dong <sanbai@taobao.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

The comment for ext4_ext_check_cache has a litte mistake.
Signed-off-by: NRobin Dong <sanbai@taobao.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

The debug message in ext4_ext_insert_extent before moving extent
is incorrect (the "from xx to xx").
Signed-off-by: NRobin Dong <sanbai@taobao.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

The argument "inode" in function ext4_ext_next_allocated_block looks useless,
so clean it.
Signed-off-by: NRobin Dong <sanbai@taobao.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

If eh_entries is equal to (or greater than) eh_max, the operation of
inserting new extent_idx will make number of entries overflow.
So check eh_entries before inserting the new extent_idx.

Although there is no bug case according the code (function
ext4_ext_insert_index is called by ext4_ext_split and ext4_ext_split
is called only if the index block has free space), the right logic
should be "lookup the capacity before insertion".
Signed-off-by: NRobin Dong <sanbai@taobao.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

This patch avoids an extraneous lookup of the extent cache
in ext4_ext_map_blocks() when the flag
EXT4_GET_BLOCKS_PUNCH_OUT_EXT is absent.

The existing logic was performing the lookup but not making
use of the result. The patch simply reverses the order of evaluation
in the condition.

Since ext4_ext_in_cache() does not initialize newex on misses, bypassing
its invocation does not introduce any new issue in this regard.
Signed-off-by: NRobin Dong <sanbai@taobao.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: NLukas Czerner <lczerner@redhat.com>
Reviewed-by: NEric Gouriou <egouriou@google.com>

This patch removes the extra parameter in ext4_ext_remove_space()
which is no longer needed.
Signed-off-by: NAllison Henderson <achender@linux.vnet.ibm.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

This patch optimizes the punch hole operation by skipping the
tree walking code that is used by truncate.  Since punch hole
is done through map blocks, the path to the extent is already
known in this function, so we do not need to look it up again.
Signed-off-by: NAllison Henderson <achender@linux.vnet.ibm.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

Optimize ext4_ext_insert_extent() by avoiding
ext4_ext_next_leaf_block() when the result is not used/needed.
Signed-off-by: NRobin Dong <sanbai@taobao.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

If eh->eh_entries is smaller than eh->eh_max, the routine will
go to the "repeat" and then go to "has_space" directlly ,
since argument "depth" and "eh" are not even changed.

Therefore, goto "has_space" directly and remove redundant "repeat" tag.
Signed-off-by: NRobin Dong <sanbai@taobao.com>

Upon corrupted inode or disk failures, we may fail after we already
allocate some blocks from the inode or take some blocks from the
inode's preallocation list, but before we successfully insert the
corresponding extent to the extent tree. In this case, we should free
any allocated blocks and discard the inode's preallocated blocks
because the entries in the inode's preallocation list may be in an
inconsistent state.
Signed-off-by: NJiaying Zhang <jiayingz@google.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org

The current implementation of ext4_free_blocks() always calls
dquot_free_block This looks quite sensible in the most cases: blocks
to be freed are associated with inode and were accounted in quota and
i_blocks some time ago.

However, there is a case when blocks to free were not accounted by the
time calling ext4_free_blocks() yet:

1. delalloc is on, write_begin pre-allocated some space in quota
2. write-back happens, ext4 allocates some blocks in ext4_ext_map_blocks()
3. then ext4_ext_map_blocks() gets an error (e.g.  ENOSPC) from
   ext4_ext_insert_extent() and calls ext4_free_blocks().

In this scenario, ext4_free_blocks() calls dquot_free_block() who, in
turn, decrements i_blocks for blocks which were not accounted yet (due
to delalloc) After clean umount, e2fsck reports something like:

> Inode 21, i_blocks is 5080, should be 5128.  Fix<y>?
because i_blocks was erroneously decremented as explained above.

The patch fixes the problem by passing the new flag
EXT4_FREE_BLOCKS_NO_QUOT_UPDATE to ext4_free_blocks(), to request
that the dquot_free_block() call be skipped.
Signed-off-by: NMaxim Patlasov <maxim.patlasov@gmail.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org

Unused variables was deleted.
Signed-off-by: NYongqiang Yang <xiaoqiangnk@gmail.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

I found that ext4_ext_find_goal() and ext4_find_near()
share the same code for returning a coloured start block
based on i_block_group.

We can refactor this into a common function so that they
don't diverge in the future.

Thanks to adilger for suggesting the new function name.
Signed-off-by: NEric Sandeen <sandeen@redhat.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

In function ext4_ext_insert_index when eh_entries of curp is
bigger than eh_max, error messages will be printed out, but the content
is about logical and ei_block, that's incorret.
Signed-off-by: NRobin Dong <sanbai@taobao.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

Currently we are not marking the extent as the last one
(FIEMAP_EXTENT_LAST) if there is a hole at the end of the file. This is
because we just do not check for it right now and continue searching for
next extent. But at the point we hit the hole at the end of the file, it
is too late.

This commit adds check for the allocated block in subsequent extent and
if there is no more extents (block = EXT_MAX_BLOCKS) just flag the
current one as the last one.

This behaviour has been spotted unintentionally by 252 xfstest, when the
test hangs out, because of wrong loop condition. However on other
filesystems (like xfs) it will exit anyway, because we notice the last
extent flag and exit.

With this patch xfstest 252 does not hang anymore, ext4 fiemap
implementation still reports bad extent type in some cases, however
this seems to be different issue.
Signed-off-by: NLukas Czerner <lczerner@redhat.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

Kazuya Mio reported that he was able to hit BUG_ON(next == lblock)
in ext4_ext_put_gap_in_cache() while creating a sparse file in extent
format and fill the tail of file up to its end. We will hit the BUG_ON
when we write the last block (2^32-1) into the sparse file.

The root cause of the problem lies in the fact that we specifically set
s_maxbytes so that block at s_maxbytes fit into on-disk extent format,
which is 32 bit long. However, we are not storing start and end block
number, but rather start block number and length in blocks. It means
that in order to cover extent from 0 to EXT_MAX_BLOCK we need
EXT_MAX_BLOCK+1 to fit into len (because we counting block 0 as well) -
and it does not.

The only way to fix it without changing the meaning of the struct
ext4_extent members is, as Kazuya Mio suggested, to lower s_maxbytes
by one fs block so we can cover the whole extent we can get by the
on-disk extent format.

Also in many places EXT_MAX_BLOCK is used as length instead of maximum
logical block number as the name suggests, it is all a bit messy. So
this commit renames it to EXT_MAX_BLOCKS and change its usage in some
places to actually be maximum number of blocks in the extent.

The bug which this commit fixes can be reproduced as follows:

 dd if=/dev/zero of=/mnt/mp1/file bs=<blocksize> count=1 seek=$((2**32-2))
 sync
 dd if=/dev/zero of=/mnt/mp1/file bs=<blocksize> count=1 seek=$((2**32-1))
Reported-by: NKazuya Mio <k-mio@sx.jp.nec.com>
Signed-off-by: NLukas Czerner <lczerner@redhat.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

Make ext4_ext_split() get extents to be moved by calculating in a statement
instead of counting in a loop.
Signed-off-by: NYongqiang Yang <xiaoqiangnk@gmail.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

Currently, an fallocate request of size slightly larger than a power of
2 is turned into two block requests, each a power of 2, with the extra
blocks pre-allocated for future use. When an application calls
fallocate, it already has an idea about how large the file may grow so
there is usually little benefit to reserve extra blocks on the
preallocation list. This reduces disk fragmentation.

Tested: fsstress. Also verified manually that fallocat'ed files are
contiguously laid out with this change (whereas without it they begin at
power-of-2 boundaries, leaving blocks in between). CPU usage of
fallocate is not appreciably higher.  In a tight fallocate loop, CPU
usage hovers between 5%-8% with this change, and 5%-7% without it.

Using a simulated file system aging program which the file system to
70%, the percentage of free extents larger than 8MB (as measured by
e2freefrag) increased from 38.8% without this change, to 69.4% with
this change.
Signed-off-by: NVivek Haldar <haldar@google.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

This patch adds new routines: "ext4_punch_hole" "ext4_ext_punch_hole"
and "ext4_ext_check_cache"

fallocate has been modified to call ext4_punch_hole when the punch hole
flag is passed.  At the moment, we only support punching holes in
extents, so this routine is pretty much a wrapper for the ext4_ext_punch_hole
routine.

The ext4_ext_punch_hole routine first completes all outstanding writes
with the associated pages, and then releases them.  The unblock
aligned data is zeroed, and all blocks in between are punched out.

The ext4_ext_check_cache routine is very similar to ext4_ext_in_cache
except it accepts a ext4_ext_cache parameter instead of a ext4_extent
parameter.  This routine is used by ext4_ext_punch_hole to check and
see if a block in a hole that has been cached.  The ext4_ext_cache
parameter is necessary because the members ext4_extent structure are
not large enough to hold a 32 bit value.  The existing
ext4_ext_in_cache routine has become a wrapper to this new function.

[ext4 punch hole patch series 5/5 v7] 
Signed-off-by: NAllison Henderson <achender@us.ibm.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: NMingming Cao <cmm@us.ibm.com>

This patch adds a new flag to ext4_map_blocks() that specifies the
given range of blocks should be punched out.  Extents are first
converted to uninitialized extents before they are punched
out. Because punching a hole may require that the extent be split, it
is possible that the splitting may need more blocks than are
available.  To deal with this, use of reserved blocks are enabled to
allow the split to proceed.

The routine then returns the number of blocks successfully
punched out.

[ext4 punch hole patch series 4/5 v7]
Signed-off-by: NAllison Henderson <achender@us.ibm.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: NMingming Cao <cmm@us.ibm.com>

This patch modifies the truncate routines to support hole punching
Below is a brief summary of the patches changes:

- Added end param to ext_ext4_rm_leaf
        This function has been modified to accept an end parameter
        which enables it to punch holes in leafs instead of just
        truncating them.

- Implemented the "remove head" case in the ext_remove_blocks routine
        This routine is used by ext_ext4_rm_leaf to remove the tail
        of an extent during a truncate.  The new ext_ext4_rm_leaf
        routine will now also use it to remove the head of an extent in the
        case that the hole covers a region of blocks at the beginning
        of an extent.

- Added "end" param to ext4_ext_remove_space routine
        This function has been modified to accept a stop parameter, which
        is passed through to ext4_ext_rm_leaf.

[ext4 punch hole patch series 3/5 v6] 
Signed-off-by: NAllison Henderson <achender@us.ibm.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

This patch adds an allocation request flag to the ext4_has_free_blocks
function which enables the use of reserved blocks.  This will allow a
punch hole to proceed even if the disk is full.  Punching a hole may
require additional blocks to first split the extents.

Because ext4_has_free_blocks is a low level function, the flag needs
to be passed down through several functions listed below:

ext4_ext_insert_extent
ext4_ext_create_new_leaf
ext4_ext_grow_indepth
ext4_ext_split
ext4_ext_new_meta_block
ext4_mb_new_blocks
ext4_claim_free_blocks
ext4_has_free_blocks

[ext4 punch hole patch series 1/5 v7]
Signed-off-by: NAllison Henderson <achender@us.ibm.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: NMingming Cao <cmm@us.ibm.com>

To get delayed-extent information, ext4_ext_fiemap_cb() looks up
pagecache, it thus collects information starting from a page's
head block.

If blocksize < pagesize, the beginning blocks of a page may lies
before the request range. So ext4_ext_fiemap_cb() should proceed
ignoring them, because they has been handled before. If no mapped
buffer in the range is found in the 1st page, we need to look up
the 2nd page, otherwise delayed-extents after a hole will be ignored.

Without this patch, xfstests 225 will hung on ext4 with 1K block.
Reported-by: NAmir Goldstein <amir73il@users.sourceforge.net>
Signed-off-by: NYongqiang Yang <xiaoqiangnk@gmail.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

ext4_ext_truncate() should not invoke up_write(&EXT4_I(inode)->i_data_sem)
when ext4_orphan_add() returns an error, as it hasn't performed a
down_write() yet. This trivial patch fixes this by moving the up_write()
invocation above the out_stop label.
Signed-off-by: NEric Gouriou <egouriou@google.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

The number of hits and misses for each filesystem is exposed in
/sys/fs/ext4/<dev>/extent_cache_{hits, misses}.

Tested: fsstress, manual checks.
Signed-off-by: NVivek Haldar <haldar@google.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

Signed-off-by: NYongqiang Yang <xiaoqiangnk@gmail.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: NMingming Cao <cmm@us.ibm.com>

This patch addresses bugs found while testing punch hole 
with the fsx test.  The patch corrects the number of blocks
that are zeroed out while splitting an extent, and also corrects
the return value to return the number of blocks split out, instead
of the number of blocks zeroed out.

This patch has been tested in addition to the following patches: 
[Ext4 punch hole v7]
[XFS Tests Punch Hole 1/1 v2] Add Punch Hole Testing to FSX

The test ran successfully for 24 hours.
Signed-off-by: NAllison Henderson <achender@us.ibm.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

Reimplement ext4_ext_convert_to_initialized() and
ext4_split_unwritten_extents() using ext4_split_extent()
Signed-off-by: NYongqiang Yang <xiaoqiangnk@gmail.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>
Tested-by: NAllison Henderson <achender@linux.vnet.ibm.com>

Add two functions: ext4_split_extent_at(), which splits an extent into
two extents at given logical block, and ext4_split_extent() which
splits an extent into three extents.
Signed-off-by: NYongqiang Yang <xiaoqiangnk@gmail.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>
Tested-by: NAllison Henderson <achender@linux.vnet.ibm.com>