linux-ext4 - Re: [PATCH 04/10 v5] ext4: track all extent status in extent status tree

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Date:	Tue, 12 Feb 2013 22:28:19 -0500
From:	Theodore Ts'o <tytso@....edu>
To:	Zheng Liu <gnehzuil.liu@...il.com>
Cc:	linux-ext4@...r.kernel.org, Zheng Liu <wenqing.lz@...bao.com>,
	Jan kara <jack@...e.cz>
Subject: Re: [PATCH 04/10 v5] ext4: track all extent status in extent status
 tree

On Fri, Feb 08, 2013 at 04:44:00PM +0800, Zheng Liu wrote:
> From: Zheng Liu <wenqing.lz@...bao.com>
> 
> By recording the phycisal block and status, extent status tree is able
> to track the status of every extents.  When we call _map_blocks
> functions to lookup an extent or create a new written/unwritten/delayed
> extent, this extent will be inserted into extent status tree.  The hole
> extent is inserted in ext4_ext_put_gap_in_cache().  If there is no any
> extent, we will not insert a hole extent [0, ~0] into the extent status
> tree in order to reduce the complextiy of code.
> 
> We don't load all extents from disk in alloc_inode() because it costs
> too much memory, and if a file is opened and closed frequently it will
> takes too much time to load all extent information.  So currently when
> we create/lookup an extent, this extent will be inserted into extent
> status tree.  Hence, the extent status tree may not comprehensively
> contain all of the extents found in the file.
> 
> Signed-off-by: Zheng Liu <wenqing.lz@...bao.com>
> Cc: "Theodore Ts'o" <tytso@....edu>
> Cc: Jan kara <jack@...e.cz>

Unfortunately, this commit is apparently causing test failures with
bigalloc:

--- 013.out	2013-01-01 22:52:04.000000000 -0500
+++ 013.out.bad	2013-02-12 22:08:47.110766615 -0500
@@ -8,7 +8,4 @@
 -----------------------------------------------
 fsstress.2 : -p 20 -r
 -----------------------------------------------
-
------------------------------------------------
-fsstress.3 : -p 4 -z -f rmdir=10 -f link=10 -f creat=10 -f mkdir=10 -f rename=30 -f stat=30 -f unlink=30 -f truncate=20
------------------------------------------------
+_check_generic_filesystem: filesystem on /dev/vdd is inconsistent (see 013.full)
_check_generic_filesystem: filesystem on /dev/vdd is inconsistent (see 013.full)
Ran: 013
Failures: 013
Failed 1 of 1 tests
END TEST: Ext4 4k block w/bigalloc Tue Feb 12 22:08:49 EST 2013
e2fsck 1.43-WIP (15-Jan-2013)
Pass 1: Checking inodes, blocks, and sizes
Inode 618, i_blocks is 1408, should be 1536.  Fix? yes

Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information

/dev/vdd: ***** FILE SYSTEM WAS MODIFIED *****
/dev/vdd: 3969/81936 files (13.1% non-contiguous), 176208/1310720 blocks


I haven't been able to figure out what is going on here, but if we
can't figure this out I may need to push off this patch series to the
next merge window.  I've tried splitting up this patch into two pieces
to make it clearer what is going on, but I still can't see how this
would be affecting the i_blocks calculation.

							- Ted


					
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