Trond Myklebust wrote:
On Wed, 2007-05-16 at 22:39 +1000, Nick Piggin wrote:
=======================
BUG: at /local/xslaby/xxx/mm/page-writeback.c:829 __set_page_dirty_nobuffers()
[<c010531e>] dump_trace+0x1ce/0x200
[<c010536a>] show_trace_log_lvl+0x1a/0x30
[<c0106012>] show_trace+0x12/0x20
[<c0106086>] dump_stack+0x16/0x20
[<c015566d>] __set_page_dirty_nobuffers+0x11d/0x130
[<f8b1fc5b>] nfs_updatepage+0x7b/0x200 [nfs]
[<f8b156df>] nfs_commit_write+0x2f/0x50 [nfs]
[<c0150911>] generic_file_buffered_write+0x2a1/0x660
[<c0150f52>] __generic_file_aio_write_nolock+0x282/0x520
[<c0151252>] generic_file_aio_write+0x62/0xd0
[<f8b15def>] nfs_file_write+0xef/0x1c0 [nfs]
[<c01715e0>] do_sync_write+0xd0/0x110
[<c0171e04>] vfs_write+0x94/0x130
[<c017248d>] sys_write+0x3d/0x70
[<c01040e8>] syscall_call+0x7/0xb
[<b7eb7b3e>] 0xb7eb7b3e
=======================
This one is NFS, setting the page dirty while it is not uptodate. Trond,
is this because NFS keeps track of dirty regions of the page with private
data? It might make sense to avoid this warning if PagePrivate is set...
would that fix the NFS case?
Ah... You put an extra WARN_ON(!PageUptodate(page)). err=-ENOCOFFEE, I
missed that...
So yes, in order to avoid having to read the page in when we just want
to write data, NFS does this kind of tracking. I dunno if your fix to
change it to !PagePrivate(page) && !PageUptodate(page) is right though.
It will indeed fix the NFS case, but the block system uses PagePrivate()
pretty extensively for its own nefarious ends (tracking page buffers).
I think that's OK: the block layer is similarly happy to mark a !uptodate
page dirty if it has buffers, for similar reasons... Anyway, it won't use
this particular path when buffers are attached, and I've put similar
debugging stuff in the set_page_dirty_buffers part.
--
SUSE Labs, Novell Inc.
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