Ext4 without journal write cache problem...

[Andrea Gelmini <andrea.gelmini@xxxxxxxxx>]

Hi all,
   I need some advice about this regression...

   Short version:
   With 2.6.32 my / partition (ext4 without journal) seems working
always in synchronous mode. No write caching, so the HD is always
working. It works as usual with 2.6.31.

   Long version:
   To replicate the problem I've used the bash script in attachment (test.sh)
   With 2.6.31.6 I have no work at all of the disk and incredible
speed results of dd (~400 MB/s), of course.
   With 2.6.32 I have the HD always working, and real speed numbers of
dd (~30MB/s).

   I bisected 2.6.32 and 2.6.31.6 version. In attach you can find the
log (bisect_log.txt).
   Reverting the last commit
(5534fb5bb35a62a94e0bd1fa2421f7fb6e894f10) gives the same behavior for
both kernel version.

   I investigated it because since using 2.6.32 my laptop temperature
became a lot higher, so much that my keybord keys were hot.
   Also, if I issue a sync I always have an immediate response, as I
was using "mount -o sync", ragrdless what I've done before.

Thanks a lot for your time and work,
Andrea

git bisect start
# bad: [745402c939529c0e11e59e7987a97becfbabff82] Merge branch 'gelma'
git bisect bad 745402c939529c0e11e59e7987a97becfbabff82
# good: [d8f879c0cc0c55cc42e9176dee5131e19a721854] Merge branch 'gelma' into t31
git bisect good d8f879c0cc0c55cc42e9176dee5131e19a721854
# good: [4d5d3932e8089ffabb1e4f9bd4d9746c8c250457] mio
git bisect good 4d5d3932e8089ffabb1e4f9bd4d9746c8c250457
# good: [6f128fa344833bf8bf076a51d14401661c146470] Merge branch 'davinci-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/khilman/linux-davinci
git bisect good 6f128fa344833bf8bf076a51d14401661c146470
# bad: [5f8fe4270e53d38421ba34c428c3b58933b48e50] Merge branch 'for-linus' of git://repo.or.cz/cris-mirror
git bisect bad 5f8fe4270e53d38421ba34c428c3b58933b48e50
# bad: [85e08ca54c5c203cd2638f0fc8fa899a539f6254] USB: Move endpoint sync type definitions from usb/audio.h to usb/ch9.h
git bisect bad 85e08ca54c5c203cd2638f0fc8fa899a539f6254
# bad: [84d6ae431f315e8973aac3c3fe1d550fc9240ef3] V4L/DVB (13033): pt1: Don't use a deprecated DMA_BIT_MASK macro
git bisect bad 84d6ae431f315e8973aac3c3fe1d550fc9240ef3
# good: [515b696b282f856c3ad1679ccd658120faa387d0] Merge git://git.kernel.org/pub/scm/linux/kernel/git/lethal/sh-2.6
git bisect good 515b696b282f856c3ad1679ccd658120faa387d0
# bad: [ecda427340b7bb5c61fbf18857645286c2bfec6c] V4L/DVB (12869): tda18271: fix comments and make tda18271_agc debug less verbose
git bisect bad ecda427340b7bb5c61fbf18857645286c2bfec6c
# bad: [3530c1886291df061e3972c55590777ef1cb67f8] Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4
git bisect bad 3530c1886291df061e3972c55590777ef1cb67f8
# good: [1f7bebb9e911d870fa8f997ddff838e82b5715ea] ext4: Always set dx_node's fake_dirent explicitly.
git bisect good 1f7bebb9e911d870fa8f997ddff838e82b5715ea
# good: [81ce31b773226332475f89501b1072bec0c0e241] Merge branch 'for-linus' of git://gitserver.sunplusct.com/linux-2.6-score
git bisect good 81ce31b773226332475f89501b1072bec0c0e241
# good: [27f5de7963f46388932472b660f2f9a86ab58454] mm: Fix problem of parameter in note
git bisect good 27f5de7963f46388932472b660f2f9a86ab58454
# good: [fb0a387dcdcd21aab1b09ee7fd80b7c979bdbbfd] ext4: limit block allocations for indirect-block files to < 2^32
git bisect good fb0a387dcdcd21aab1b09ee7fd80b7c979bdbbfd
# bad: [0a80e9867db154966b2a771042e10452ac110e1e] ext4: replace MAX_DEFRAG_SIZE with EXT_MAX_BLOCK
git bisect bad 0a80e9867db154966b2a771042e10452ac110e1e
# good: [fb40ba0d98968bc3454731360363d725b4f1064c] ext4: Add a tracepoint for ext4_alloc_da_blocks()
git bisect good fb40ba0d98968bc3454731360363d725b4f1064c
# bad: [5534fb5bb35a62a94e0bd1fa2421f7fb6e894f10] ext4: Fix the alloc on close after a truncate hueristic
git bisect bad 5534fb5bb35a62a94e0bd1fa2421f7fb6e894f10

Attachment: test.sh
Description: Bourne shell script

Filesystem volume name:   /
Last mounted on:          /
Filesystem UUID:          a7d58ef8-6698-427c-bc0e-08fd79f0e847
Filesystem magic number:  0xEF53
Filesystem revision #:    1 (dynamic)
Filesystem features:      ext_attr resize_inode dir_index filetype extent flex_bg sparse_super large_file uninit_bg dir_nlink extra_isize
Filesystem flags:         signed_directory_hash 
Default mount options:    journal_data_writeback
Filesystem state:         not clean
Errors behavior:          Continue
Filesystem OS type:       Linux
Inode count:              2970064
Block count:              104871292
Reserved block count:     0
Free blocks:              30976496
Free inodes:              2268721
First block:              1
Block size:               1024
Fragment size:            1024
Reserved GDT blocks:      39
Blocks per group:         8192
Fragments per group:      8192
Inodes per group:         232
Inode blocks per group:   58
Flex block group size:    16
Filesystem created:       Sat Nov 21 20:44:04 2009
Last mount time:          Sun Dec  6 12:49:47 2009
Last write time:          Sun Dec  6 12:51:05 2009
Mount count:              27
Maximum mount count:      365
Last checked:             Sat Nov 28 12:53:41 2009
Check interval:           31104000 (12 months)
Next check after:         Tue Nov 23 12:53:41 2010
Lifetime writes:          208 GB
Reserved blocks uid:      0 (user root)
Reserved blocks gid:      0 (group root)
First inode:              11
Inode size:	          256
Required extra isize:     28
Desired extra isize:      28
Default directory hash:   half_md4
Directory Hash Seed:      42e8029a-d8d9-4f6b-8ddb-26d88b3765b4