On Thu, Jun 02, 2016 at 02:17:50PM +0200, Jan Kara wrote:
>
> So I was trying but I could not reproduce the hang either. Can you find out
> which page is jbd2 thread waiting for and dump page->index, page->flags and
> also bh->b_state, bh->b_blocknr of all 4 buffer heads attached to it via
> page->private? Maybe that will shed some light...
I'm using crash on live system when the hang happens, so I got the page
address from "bt -f"
#6 [ffff880212343b40] wait_on_page_bit at ffffffff8119009e
ffff880212343b48: ffffea0002c23600 000000000000000d
ffff880212343b58: 0000000000000000 0000000000000000
ffff880212343b68: ffff880213251480 ffffffff810cd000
ffff880212343b78: ffff88021ff27218 ffff88021ff27218
ffff880212343b88: 00000000c1b4a75a ffff880212343c68
ffff880212343b98: ffffffff811901bf
The call is "wait_on_page_bit(page, PG_writeback);" and PG_writeback is
13 of type enum, which is 0xd in hex. So ffffea0002c23600 might be the
page address. (Confirmed by following the page to the correct inode)
So page->index:
crash> page ffffea0002c23600 | grep index
index = 2441406,
page->flags:
crash> page ffffea0002c23600 | grep flags
flags = 9007197107267616,
crash> eval 9007197107267616
hexadecimal: 1fffff80002820
decimal: 9007197107267616
octal: 377777760000024040
binary: 0000000000011111111111111111111110000000000000000010100000100000
page->private:
crash> page ffffea0002c23600 | grep private
private = 18446612141237651696,
crash> eval 18446612141237651696
hexadecimal: ffff880213e0c8f0
The 4 buffer heads:
crash> buffer_head ffff880213e0c8f0
struct buffer_head {
b_state = 0,
b_this_page = 0xffff880213e0c958,
b_page = 0xffffea0002c23600,
b_blocknr = 18446744073709551615,
b_size = 1024,
b_data = 0xffff8800b08d8000 "",
b_bdev = 0x0,
b_end_io = 0x0,
b_private = 0x0,
b_assoc_buffers = {
next = 0xffff880213e0c938,
prev = 0xffff880213e0c938
},
b_assoc_map = 0x0,
b_count = {
counter = 0
}
}
crash> buffer_head 0xffff880213e0c958
struct buffer_head {
b_state = 289,
b_this_page = 0xffff880213e0c9c0,
b_page = 0xffffea0002c23600,
b_blocknr = 19194,
b_size = 1024,
b_data = 0xffff8800b08d8400 "a",
b_bdev = 0xffff8802152009c0,
b_end_io = 0x0,
b_private = 0x0,
b_assoc_buffers = {
next = 0xffff880213e0c9a0,
prev = 0xffff880213e0c9a0
},
b_assoc_map = 0x0,
b_count = {
counter = 0
}
}
crash> buffer_head 0xffff880213e0c9c0
struct buffer_head {
b_state = 1,
b_this_page = 0xffff880213e0ca28,
b_page = 0xffffea0002c23600,
b_blocknr = 18446744073709551615,
b_size = 1024,
b_data = 0xffff8800b08d8800 "",
b_bdev = 0x0,
b_end_io = 0x0,
b_private = 0x0,
b_assoc_buffers = {
next = 0xffff880213e0ca08,
prev = 0xffff880213e0ca08
},
b_assoc_map = 0x0,
b_count = {
counter = 0
}
}
crash> buffer_head 0xffff880213e0ca28
struct buffer_head {
b_state = 1,
b_this_page = 0xffff880213e0c8f0,
b_page = 0xffffea0002c23600,
b_blocknr = 18446744073709551615,
b_size = 1024,
b_data = 0xffff8800b08d8c00 "",
b_bdev = 0x0,
b_end_io = 0x0,
b_private = 0x0,
b_assoc_buffers = {
next = 0xffff880213e0ca70,
prev = 0xffff880213e0ca70
},
b_assoc_map = 0x0,
b_count = {
counter = 0
}
}
If you need anything else please let me know.
And just a follow-up on the testing with different kernel configs, I can
still reproduce the hang easily with OpenSuSE based kernel, and I still
have trouble booting the kernel compiled with Ted's config file... Maybe
it's missing some modules, but there're so many of them, I trend to give
up :)
Thanks,
Eryu
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