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SubjectRe: [BUG - btrfs] kernel oops in extent_range_uptodate
On Wed, Jan 25, 2012 at 04:30, Mitch Harder
<mitch.harder@sabayonlinux.org> wrote:
>
> On Tue, Jan 24, 2012 at 10:24 AM, Vincent Vanackere
> <vincent.vanackere@gmail.com> wrote:
> > On 01/20/2012 09:54 PM, Mitch Harder wrote:
> >>
> >> On Fri, Jan 20, 2012 at 10:48 AM, Vincent Vanackere
> >> <vincent.vanackere@gmail.com>  wrote:
> >>>
> >>> On 01/19/2012 05:24 PM, Mitch Harder wrote:
> >>>>
> >>>> On Thu, Jan 19, 2012 at 8:42 AM, Vincent Vanackere
> >>>> <vincent.vanackere@gmail.com>    wrote:
> >>>>>
> >>>>> Hi,
> >>>>>
> >>>>> With the most current git kernel
> >>>>> (90a4c0f51e8e44111a926be6f4c87af3938a79c3)
> >>>>> I'm still getting the same reproducible kernel panic when trying to
> >>>>> read
> >>>>> a
> >>>>> particular file stored on a btrfs filesystem (as seen in the log there
> >>>>> are
> >>>>> indeed disk media errors on this disk).
> >>>>> I'd like the "software" part of this to be fixed - btrfs should
> >>>>> definitely
> >>>>> not oops even in case of media error - before sending the disk to RMA.
> >>>>> Is
> >>>>> there anything I can do to make progress on this ?
> >>>>>
> >>>> Is this kernel compiled with "Compile the kernel with debug info" (in
> >>>> the "Kernel hacking  --->" configuration section)?
> >>>>
> >>>> It would be nice to have the specific line of code passing the NULL
> >>>> pointer.
> >>>
> >>>
> >>> The kernel was compiled with debug information but modern linux
> >>> distribution
> >>> make it really hard to keep your debug information it seems :-(
> >>
> >> I see where the find_get_page(...) function called in
> >> extent_range_uptodate has the potential to return a NULL value.
> >>
> >> Could you try the following patch, and if it solves your oops and
> >> shows the included warning in your dmesg log, I'll simplify the patch
> >> to drop the printk and submit it to the list.
> >>
> >> I only included the printk since your current error log is ambiguous
> >> regarding the specific point where we're getting the NULL pointer
> >> dereference, but I'll pull it out if it works.
> >>
> >> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> >> index 9d09a4f..35c3a2a 100644
> >> --- a/fs/btrfs/extent_io.c
> >> +++ b/fs/btrfs/extent_io.c
> >> @@ -3909,6 +3909,13 @@ int extent_range_uptodate(struct extent_io_tree
> >> *tree,
> >>        while (start<= end) {
> >>                index = start>>  PAGE_CACHE_SHIFT;
> >>                page = find_get_page(tree->mapping, index);
> >> +               if (unlikely(!page)) {
> >> +                       if (printk_ratelimit())
> >> +                               printk(KERN_WARNING
> >> +                                      "btrfs: NULL page in "
> >> +                                      "extent_range_uptodate()\n");
> >> +                       return 1;
> >> +               }
> >>                uptodate = PageUptodate(page);
> >>                page_cache_release(page);
> >>                if (!uptodate) {
> >
> >
> > Indeed your patch helps. No kernel panic any more... but it looks like the
> > task doesn't finish and there's another problem to solve now :
> >
> >
> > sd 5:0:0:0: [sdd] Unhandled sense code
> > sd 5:0:0:0: [sdd]  Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
> > sd 5:0:0:0: [sdd]  Sense Key : Medium Error [current] [descriptor]
> > Descriptor sense data with sense descriptors (in hex):
> >        72 03 11 04 00 00 00 0c 00 0a 80 00 00 00 00 00
> >        70 2f dc 61
> > sd 5:0:0:0: [sdd]  Add. Sense: Unrecovered read error - auto reallocate
> > failed
> > sd 5:0:0:0: [sdd] CDB: Read(10): 28 00 70 2f dc 5f 00 00 08 00
> > end_request: I/O error, dev sdd, sector 1882184801
> > ata6: EH complete
> > btrfs: NULL page in extent_range_uptodate()
> > btrfs: NULL page in extent_range_uptodate()
> > btrfs bad tree block start 959241011200 959241011200
> > INFO: task cat:3099 blocked for more than 120 seconds.
> > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > cat             D ffffffff8180c600     0  3099   3002 0x00000000
> >  ffff8801f2b0f618 0000000000000086 ffff8801f2b0f5d8 ffff880221018770
> >  ffff880222c65b80 ffff8801f2b0ffd8 ffff8801f2b0ffd8 ffff8801f2b0ffd8
> >  ffff8802241816e0 ffff880222c65b80 ffff8801f2b0f5e8 ffff88022fd13e88
> > Call Trace:
> >  [<ffffffff81114260>] ? __lock_page+0x70/0x70
> >  [<ffffffff8162c93f>] schedule+0x3f/0x60
> >  [<ffffffff8162c9ef>] io_schedule+0x8f/0xd0
> >  [<ffffffff8111426e>] sleep_on_page+0xe/0x20
> >  [<ffffffff8162b1ff>] __wait_on_bit+0x5f/0x90
> >  [<ffffffff811143d8>] wait_on_page_bit+0x78/0x80
> >  [<ffffffff81070c40>] ? autoremove_wake_function+0x40/0x40
> >  [<ffffffffa0192161>] read_extent_buffer_pages+0x471/0x4d0 [btrfs]
> >  [<ffffffffa01697b0>] ? verify_parent_transid+0x160/0x160 [btrfs]
> >  [<ffffffffa016a13a>] btree_read_extent_buffer_pages.isra.99+0x8a/0xc0
> > [btrfs]
> >  [<ffffffffa016c1e1>] read_tree_block+0x41/0x60 [btrfs]
> >  [<ffffffffa01526a3>] read_block_for_search.isra.34+0xf3/0x3d0 [btrfs]
> >  [<ffffffffa0154930>] btrfs_search_slot+0x300/0x8a0 [btrfs]
> >  [<ffffffffa0166ab4>] btrfs_lookup_csum+0x74/0x170 [btrfs]
> >  [<ffffffffa0166d5f>] __btrfs_lookup_bio_sums+0x1af/0x3b0 [btrfs]
> >  [<ffffffffa0166fb6>] btrfs_lookup_bio_sums+0x16/0x20 [btrfs]
> >  [<ffffffffa0173650>] btrfs_submit_bio_hook+0x140/0x170 [btrfs]
> >  [<ffffffffa01755d0>] ? btrfs_real_readdir+0x720/0x720 [btrfs]
> >  [<ffffffffa018c17a>] submit_one_bio+0x6a/0xa0 [btrfs]
> >  [<ffffffffa0190e34>] extent_readpages+0xe4/0x100 [btrfs]
> >  [<ffffffffa01755d0>] ? btrfs_real_readdir+0x720/0x720 [btrfs]
> >  [<ffffffffa0173ebf>] btrfs_readpages+0x1f/0x30 [btrfs]
> >  [<ffffffff81120a0f>] __do_page_cache_readahead+0x1af/0x250
> >  [<ffffffff81120e11>] ra_submit+0x21/0x30
> >  [<ffffffff81120f35>] ondemand_readahead+0x115/0x230
> >  [<ffffffff81137cd9>] ? __do_fault+0x419/0x530
> >  [<ffffffff81121131>] page_cache_sync_readahead+0x31/0x50
> >  [<ffffffff811165f8>] generic_file_aio_read+0x438/0x780
> >  [<ffffffff81173bb2>] do_sync_read+0xd2/0x110
> >  [<ffffffff81293e73>] ? security_file_permission+0x93/0xb0
> >  [<ffffffff81174031>] ? rw_verify_area+0x61/0xf0
> >  [<ffffffff81174510>] vfs_read+0xb0/0x180
> >  [<ffffffff8117462a>] sys_read+0x4a/0x90
> >  [<ffffffff81635ae9>] system_call_fastpath+0x16/0x1b
> >
>
> Good, looks like we're making progress.
>
> We appear to be stuck now at wait_on_page_locked(page) in the
> read_extent_buffer_pages(...) function in extent_io.c
>
>        for (i = start_i; i < num_pages; i++) {
>                page = extent_buffer_page(eb, i);
>                wait_on_page_locked(page);
>                if (!PageUptodate(page))
>                        ret = -EIO;
>        }
>
> I tried looking around the kernel for how others have handled error
> checking when using wait_on_page_locked(...), but I could not find
> many examples.
>
> http://lxr.free-electrons.com/ident?i=wait_on_page_locked
>
> I believe I'll have to ask for help from the others on the list at
> this point for how to handle this issue.
>
> Do you still have data you are trying to recover from this disk?

I already recovered all interesting data, I'm only keeping this disk
until I'm confident btrfs will be able to deal with this particular IO
error... Thanks for your help so far !

Vincent
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