Re: Oops on btrfs filesystem balance

[Wu Fengguang]

On Fri, Mar 26, 2010 at 11:40:51AM +0800, Yan, Zheng  wrote:
> On Thu, Mar 25, 2010 at 9:06 PM, Kirill A. Shutemov
> <kirill@xxxxxxxxxxxxx> wrote:
> > On lastest Linus' git.
> >
> > [ 4005.426805] BUG: unable to handle kernel NULL pointer dereference at 00000021
> > [ 4005.426818] IP: [<c109a130>] page_cache_sync_readahead+0x18/0x3e
> > [ 4005.426837] *pde = 00000000
> > [ 4005.426844] Oops: 0000 [#1] PREEMPT SMP
> > [ 4005.426854] last sysfs file:
> > /sys/devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:00/PNP0C09:00/PNP0C0A:00/power_supply/BAT0/energy_full
> > [ 4005.426864] Modules linked in: btrfs zlib_deflate crc32c libcrc32c
> > loop coretemp ext2 arc4 ecb iwlagn iwlcore snd_hda_codec_conexant
> > snd_hda_intel mac80211 snd_hda_codec snd_hwdep snd_pcm snd_timer snd
> > uvcvideo e1000e rtc_cmos rtc_core cdc_ether videodev uhci_hcd usbnet
> > sg snd_page_alloc video thinkpad_acpi cdc_acm rtc_lib v4l1_compat mii
> > output ext3 jbd usbhid sd_mod sha256_generic cbc ata_piix ehci_hcd
> > aes_i586 aes_generic libata dm_crypt usbcore scsi_mod nls_base dm_mod
> > [ 4005.426971]
> > [ 4005.426979] Pid: 25838, comm: btrfs Not tainted 2.6.34-rc2 #67
> > 2767BC8/2767BC8
> > [ 4005.426987] EIP: 0060:[<c109a130>] EFLAGS: 00010206 CPU: 0
> > [ 4005.426996] EIP is at page_cache_sync_readahead+0x18/0x3e
> > [ 4005.427002] EAX: f58dcb84 EBX: 00000000 ECX: 00000000 EDX: f45efe40
> > [ 4005.427009] ESI: 00033b43 EDI: f58dcad4 EBP: f4b61ce0 ESP: f4b61cd8
> > [ 4005.427010] ÂDS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
> > [ 4005.427010] Process btrfs (pid: 25838, ti=f4b60000 task=f6680a60
> > task.ti=f4b60000)
> > [ 4005.427010] Stack:
> > [ 4005.427010] Â41c00001 00000001 f4b61d50 f9443902 00000000 00033b43
> > f93fc3dc f6bf4d80
> > [ 4005.427010] <0> f4cc74d0 41c00001 00000001 f58dcb4c 00033b42
> > f58dc9e0 f72e7600 f4b61d2c
> > [ 4005.427010] <0> f45efe40 00000000 00000000 00033b43 41c00000
> > 00000001 00000000 00000000
> > [ 4005.427010] Call Trace:
> > [ 4005.427010] Â[<f9443902>] ? relocate_file_extent_cluster+0x195/0x3bd [btrfs]
> > [ 4005.427010] Â[<f93fc3dc>] ? btrfs_release_path+0x39/0x4a [btrfs]
> > [ 4005.427010] Â[<f9444bd2>] ? relocate_block_group+0x2be/0x32a [btrfs]
> > [ 4005.427010] Â[<f9411dd3>] ? btrfs_clean_old_snapshots+0x66/0xd9 [btrfs]
> > [ 4005.427010] Â[<f9444d87>] ? btrfs_relocate_block_group+0x149/0x2e3 [btrfs]
> > [ 4005.427010] Â[<f942eecc>] ? btrfs_relocate_chunk+0x5c/0x423 [btrfs]
> > [ 4005.427010] Â[<c10217cc>] ? kmap_atomic+0x13/0x15
> > [ 4005.427010] Â[<f9428f32>] ? map_private_extent_buffer+0x94/0xb6 [btrfs]
> > [ 4005.427010] Â[<f9428fa3>] ? map_extent_buffer+0x4f/0x7f [btrfs]
> > [ 4005.427010] Â[<c10216d3>] ? kunmap_atomic+0x6c/0x83
> > [ 4005.427010] Â[<f9428aca>] ? unmap_extent_buffer+0x11/0x13 [btrfs]
> > [ 4005.427010] Â[<f94206dd>] ? btrfs_item_offset+0x98/0xa2 [btrfs]
> > [ 4005.427010] Â[<f942f856>] ? btrfs_balance+0x20f/0x265 [btrfs]
> > [ 4005.427010] Â[<f9436ab9>] ? btrfs_ioctl+0x6ad/0x824 [btrfs]
> > [ 4005.427010] Â[<c10bf8e1>] ? __memcg_event_check+0x50/0x72
> > [ 4005.427010] Â[<c11461e2>] ? file_has_perm+0x8c/0xa6
> > [ 4005.427010] Â[<c10cf310>] ? vfs_ioctl+0x2c/0x96
> > [ 4005.427010] Â[<f943640c>] ? btrfs_ioctl+0x0/0x824 [btrfs]
> > [ 4005.427010] Â[<c10cf8ac>] ? do_vfs_ioctl+0x48e/0x4cc
> > [ 4005.427010] Â[<c11463ca>] ? selinux_file_ioctl+0x43/0x46
> > [ 4005.427010] Â[<c10cf930>] ? sys_ioctl+0x46/0x66
> > [ 4005.427010] Â[<c132ae88>] ? syscall_call+0x7/0xb
> > [ 4005.427010] Code: 8b 48 24 85 c9 74 04 31 d2 ff d1 8d 65 f4 5b 5e
> > 5f c9 c3 55 89 e5 56 53 0f 1f 44 00 00 89 cb 8b 75 0c 8b 4d 08 83 7a
> > 0c 00 74 1f <f6> 43 21 10 74 0b 89 da 56 e8 f5 fc ff ff 5b eb 0e 56 51
> > 89 d9
> > [ 4005.427010] EIP: [<c109a130>] page_cache_sync_readahead+0x18/0x3e
> > SS:ESP 0068:f4b61cd8
> > [ 4005.427010] CR2: 0000000000000021
> > [ 4005.427898] ---[ end trace 0e53ab674cd5bfb9 ]---
> >
> 
> The 'filp' parameter for page_cache_sync_readahead is NULL in this case.
> Commit 0141450f66c3c12a3aaa869748caa64241885cdf  added code that
> dereference 'filp'.
> 
> Fengguang, would you please fix this.

Ah Sorry! Here is the patch.

Andrew and Greg: this should go for .34 and .33-stable after Kirill's
confirmation, thanks!

Thanks,
Fengguang
---
Subject: readahead: fix NULL filp dereference
From: Wu Fengguang <fengguang.wu@xxxxxxxxx>
Date: Fri Mar 26 11:53:32 CST 2010

The btrfs relocate_file_extent_cluster() calls us with NULL filp:

  [ 4005.426805] BUG: unable to handle kernel NULL pointer dereference at 00000021
  [ 4005.426818] IP: [<c109a130>] page_cache_sync_readahead+0x18/0x3e

Fix it.

CC: Yan Zheng <yanzheng@xxxxxxxx>
Reported-by: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx>
Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
---
 mm/readahead.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- sound-2.6.orig/mm/readahead.c	2010-03-26 11:51:57.000000000 +0800
+++ sound-2.6/mm/readahead.c	2010-03-26 11:52:11.000000000 +0800
@@ -502,7 +502,7 @@ void page_cache_sync_readahead(struct ad
 		return;
 
 	/* be dumb */
-	if (filp->f_mode & FMODE_RANDOM) {
+	if (filp && (filp->f_mode & FMODE_RANDOM)) {
 		force_page_cache_readahead(mapping, filp, offset, req_size);
 		return;
 	}
--
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