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Date: Sat, 05 Sep 2009 00:43:30 +0800
From: Peng Tao <bergwolf@...il.com>
To: Akira Fujita <a-fujita@...jp.nec.com>
CC: Greg Freemyer <greg.freemyer@...il.com>,
Theodore Tso <tytso@....edu>, linux-ext4@...r.kernel.org
Subject: Re: [PATCH 3/4]ext4: Return exchanged blocks count to user space
in failure
Hi, Akira,
Akira Fujita wrote:
> Hi Peng,
> Peng Tao wrote:
>> Hi, Greg,
>>
>> On Thu, Sep 3, 2009 at 4:59 AM, Greg Freemyer<greg.freemyer@...il.com> wrote:
>>> Peng,
>>>
>>> I have not looked at the code very closely, but can you tell me where
>>> a file corruption can take place? Not completing the replacement of
>>> extents with donor extents is one thing. Corrupting the original file
>>> contents is another.
>> The file corruption is mainly because of the half done replacement.
>>
>> My test case is here:
>> http://marc.info/?l=linux-ext4&m=124992522305319&w=2
>>
>
> This patch solves your test case problem.
>
>> $dd if=/dev/zero of=zero.img bs=10M count=0 seek=50
>> $dd if=../609xp.img of=first.img bs=10M count=1
>> $dd if=/dev/zero of=first.img bs=10M count=0 seek=50
>> $dd if=../609xp.img of=last.img bs=10M count=1 seek=49
>> $dd if=../609xp.img of=middle.img bs=10M count=1 seek=24
>> $dd if=/dev/zero of=middle.img bs=10M count=0 seek=50
>
>
> This problem is caused by the fact that logical offset of
> orig file is different from donor file's.
> To detect the logical offset difference in EXT4_IOC_MOVE_EXT,
> add checks to mext_calc_swap_extents() and handles it as error,
> since data exchange must be done between the same blocks.
>
> Note: This problem does not happen in ext4 online defrag
> (means with e4defrag command), because the donor file
> which is created by e4defrag in user space is
> file constitution same as orig file.
>
> And add the extent null check to ext_get_path() for
> followings test case.
>> $dd if=/dev/zero of=zero.img bs=10M count=0 seek=50
>
> More test cases are needed for EXT4_IOC_MOVE_EXT,
> so this patch may not be complete,
> but the problem you reported is fixed at least.
> I am now testing EXT4_IOC_MOVE_EXT hard.
>
> BTW, I'm now looking into the empty extent issue which
> you reported, so I will release the patch soon.
> http://marc.info/?l=linux-ext4&m=124975192830024&w=2
>
> Could you do your test case again with this patch?
After applying the two patches, I run my test case with first.img as the orig file (and middle.img or
last.img as donor file). My kernel panics and I find following message in /var/log/messages after reboot:
Sep 4 23:21:05 bergwolf -- MARK --
[ 3183.602852] Modules linked in: ext4 ppdev lp parport binfmt_misc i915 kvm_intel kvm uinput ipv6 cpufreq_userspace cpufreq_conservative cpufreq_powersave jbd2 crc16 fuse dm_snapshot dm_mirror dm_region_hash dm_log dm_mod zlib_deflate crc32c acpi_cpufreq sbp2 snd_hda_codec_analog snd_hda_intel snd_hda_codec snd_pcm_oss snd_mixer_oss pcmcia rtc_cmos snd_pcm rtc_core i2c_i801 rtc_lib snd_timer snd_page_alloc psmouse yenta_socket rsrc_nonstatic thinkpad_acpi pcmcia_core serio_raw evdev uhci_hcd firewire_ohci firewire_core crc_itu_t video output ehci_hcd e1000e usbcore [last unloaded: ext4]
[ 3183.602951]
[ 3183.602958] Pid: 6937, comm: a.out Not tainted (2.6.31-rc2-drm-intel-next #2) 7676A26
[ 3183.602965] EIP: 0060:[<c01cfa26>] EFLAGS: 00210287 CPU: 1
[ 3183.602977] EIP is at journal_start+0x39/0xb9
[ 3183.602982] EAX: f61a2a80 EBX: f26f048c ECX: f6995200 EDX: f6995000
[ 3183.602988] ESI: f26f048c EDI: f6f59c88 EBP: f1a77c90 ESP: f1a77c7c
[ 3183.602994] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068
[ 3183.603010] 00000002 f6995000 f6f59c88 f26f048c f6f59c88 f1a77c98 c01c9cc6 f1a77cac
[ 3183.603024] <0> c01c0b51 f6f59c88 00000001 f6995200 f1a77cc0 c0192799 004cba00 f6f59c88
[ 3183.603039] <0> f68b3840 f1a77cd4 c018ab14 004cba00 00000000 ff7fc000 f1a77d44 c015c7ec
[ 3183.603070] [<c01c9cc6>] ? ext3_journal_start_sb+0x40/0x42
[ 3183.603076] [<c01c0b51>] ? ext3_dirty_inode+0x24/0x67
[ 3183.603087] [<c0192799>] ? __mark_inode_dirty+0x23/0xc6
[ 3183.603097] [<c018ab14>] ? file_update_time+0x7a/0xa3
[ 3183.603108] [<c015c7ec>] ? __generic_file_aio_write_nolock+0x2d6/0x3fe
[ 3183.603151] [<fa29d3b4>] ? ext4_ext_find_extent+0x3f/0x230 [ext4]
[ 3183.603161] [<c015d0e3>] ? generic_file_aio_write+0x57/0xb4
[ 3183.603200] [<fa2a6c26>] ? mext_replace_branches+0x31f/0x329 [ext4]
[ 3183.603209] [<c01bef56>] ? ext3_file_write+0x1a/0x88
[ 3183.603219] [<c017b6e2>] ? do_sync_write+0xab/0xe9
[ 3183.603229] [<c0137403>] ? autoremove_wake_function+0x0/0x33
[ 3183.603239] [<c013dbda>] ? getnstimeofday+0x52/0xda
[ 3183.603249] [<c014d027>] ? do_acct_process+0x68d/0x6b2
[ 3183.603257] [<c015b46c>] ? find_get_page+0x1d/0x81
[ 3183.603268] [<c018df9f>] ? mntput_no_expire+0x19/0xb3
[ 3183.603276] [<c017c9c7>] ? __fput+0x17c/0x184
[ 3183.603286] [<c014d09f>] ? acct_process+0x53/0x66
[ 3183.603294] [<c012a318>] ? do_exit+0x174/0x573
[ 3183.603303] [<c012a778>] ? do_group_exit+0x61/0x88
[ 3183.603311] [<c012a7b2>] ? sys_exit_group+0x13/0x17
[ 3183.603320] [<c0102994>] ? sysenter_do_call+0x12/0x28
[ 3183.603419] ---[ end trace cba419e95b73d96f ]---
I'm not sure why ext3 journal is involved. I've run the case twice and both
turned out with the same trace messages.
>
> # Before you apply this patch,
> # apply following patch which I sent before:
> http://marc.info/?l=linux-ext4&m=125186152727422&w=2
>
> Regards,
> Akira Fujita
>
> ---
> fs/ext4/move_extent.c | 56 ++++++++++++++++++++++++++++++++----------------
> 1 files changed, 37 insertions(+), 19 deletions(-)
>
> diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
> index 0d10f8b..052acd9 100644
> --- a/fs/ext4/move_extent.c
> +++ b/fs/ext4/move_extent.c
> @@ -25,6 +25,8 @@
> if (IS_ERR(path)) { \
> ret = PTR_ERR(path); \
> path = NULL; \
> + } else if (path[ext_depth(inode)].p_ext == NULL) { \
> + ret = -ENODATA; \
> } \
> } while (0)
>
> @@ -284,7 +286,7 @@ mext_insert_across_blocks(handle_t *handle, struct inode *orig_inode,
>
> if (new_flag) {
> get_ext_path(orig_path, orig_inode, eblock, err);
> - if (orig_path == NULL)
> + if (err)
> goto out;
>
> if (ext4_ext_insert_extent(handle, orig_inode,
> @@ -295,7 +297,7 @@ mext_insert_across_blocks(handle_t *handle, struct inode *orig_inode,
> if (end_flag) {
> get_ext_path(orig_path, orig_inode,
> le32_to_cpu(end_ext->ee_block) - 1, err);
> - if (orig_path == NULL)
> + if (err)
> goto out;
>
> if (ext4_ext_insert_extent(handle, orig_inode,
> @@ -554,8 +556,10 @@ mext_leaf_block(handle_t *handle, struct inode *orig_inode,
> * @orig_off: block offset of original inode
> * @donor_off: block offset of donor inode
> * @max_count: the maximun length of extents
> + *
> + * Return 0 on success, or a negative error value on failure.
> */
> -static void
> +static int
> mext_calc_swap_extents(struct ext4_extent *tmp_dext,
> struct ext4_extent *tmp_oext,
> ext4_lblk_t orig_off, ext4_lblk_t donor_off,
> @@ -564,6 +568,19 @@ mext_calc_swap_extents(struct ext4_extent *tmp_dext,
> ext4_lblk_t diff, orig_diff;
> struct ext4_extent dext_old, oext_old;
>
> + BUG_ON(orig_off != donor_off);
> +
> + /* original and donor extents have to cover the same block offset */
> + if (orig_off < le32_to_cpu(tmp_oext->ee_block) ||
> + le32_to_cpu(tmp_oext->ee_block) +
> + ext4_ext_get_actual_len(tmp_oext) - 1 < orig_off)
> + return -ENODATA;
> +
> + if (orig_off < le32_to_cpu(tmp_dext->ee_block) ||
> + le32_to_cpu(tmp_dext->ee_block) +
> + ext4_ext_get_actual_len(tmp_dext) - 1 < orig_off)
> + return -ENODATA;
> +
> dext_old = *tmp_dext;
> oext_old = *tmp_oext;
>
> @@ -591,6 +608,8 @@ mext_calc_swap_extents(struct ext4_extent *tmp_dext,
>
> copy_extent_status(&oext_old, tmp_dext);
> copy_extent_status(&dext_old, tmp_oext);
> +
> + return 0;
> }
>
> /**
> @@ -632,12 +651,12 @@ mext_replace_branches(handle_t *handle, struct inode *orig_inode,
>
> /* Get the original extent for the block "orig_off" */
> get_ext_path(orig_path, orig_inode, orig_off, err);
> - if (orig_path == NULL)
> + if (err)
> goto out;
>
> /* Get the donor extent for the head */
> get_ext_path(donor_path, donor_inode, donor_off, err);
> - if (donor_path == NULL)
> + if (err)
> goto out;
> depth = ext_depth(orig_inode);
> oext = orig_path[depth].p_ext;
> @@ -647,8 +666,10 @@ mext_replace_branches(handle_t *handle, struct inode *orig_inode,
> dext = donor_path[depth].p_ext;
> tmp_dext = *dext;
>
> - mext_calc_swap_extents(&tmp_dext, &tmp_oext, orig_off,
> + err = mext_calc_swap_extents(&tmp_dext, &tmp_oext, orig_off,
> donor_off, count);
> + if (err)
> + goto out;
>
> /* Loop for the donor extents */
> while (1) {
> @@ -679,7 +700,7 @@ mext_replace_branches(handle_t *handle, struct inode *orig_inode,
> if (orig_path)
> ext4_ext_drop_refs(orig_path);
> get_ext_path(orig_path, orig_inode, orig_off, err);
> - if (orig_path == NULL)
> + if (err)
> goto out;
> depth = ext_depth(orig_inode);
> oext = orig_path[depth].p_ext;
> @@ -694,7 +715,7 @@ mext_replace_branches(handle_t *handle, struct inode *orig_inode,
> ext4_ext_drop_refs(donor_path);
> get_ext_path(donor_path, donor_inode,
> donor_off, err);
> - if (donor_path == NULL)
> + if (err)
> goto out;
> depth = ext_depth(donor_inode);
> dext = donor_path[depth].p_ext;
> @@ -705,9 +726,10 @@ mext_replace_branches(handle_t *handle, struct inode *orig_inode,
> }
> tmp_dext = *dext;
>
> - mext_calc_swap_extents(&tmp_dext, &tmp_oext, orig_off,
> - donor_off,
> - count - replaced_count);
> + err = mext_calc_swap_extents(&tmp_dext, &tmp_oext, orig_off,
> + donor_off, count - replaced_count);
> + if (err)
> + goto out;
> }
>
> out:
> @@ -1147,20 +1169,16 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp,
> len -= block_end - file_end;
>
> get_ext_path(orig_path, orig_inode, block_start, ret);
> - if (orig_path == NULL)
> + if (ret)
> goto out2;
>
> /* Get path structure to check the hole */
> get_ext_path(holecheck_path, orig_inode, block_start, ret);
> - if (holecheck_path == NULL)
> + if (ret)
> goto out;
>
> depth = ext_depth(orig_inode);
> ext_cur = holecheck_path[depth].p_ext;
> - if (ext_cur == NULL) {
> - ret = -EINVAL;
> - goto out;
> - }
>
> /*
> * Get proper extent whose ee_block is beyond block_start
> @@ -1283,7 +1301,7 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp,
> ext4_ext_drop_refs(holecheck_path);
> get_ext_path(holecheck_path, orig_inode,
> seq_start, ret);
> - if (holecheck_path == NULL)
> + if (ret)
> break;
> depth = holecheck_path->p_depth;
>
> @@ -1291,7 +1309,7 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp,
> if (orig_path)
> ext4_ext_drop_refs(orig_path);
> get_ext_path(orig_path, orig_inode, seq_start, ret);
> - if (orig_path == NULL)
> + if (ret)
> break;
>
> ext_cur = holecheck_path[depth].p_ext;
>
--
Best Regards,
Peng Tao
State Key Laboratory of Networking and Switching Technology
Beijing Univ. of Posts and Telecoms.
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