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SubjectRe: [PATCH] aio: fix kernel bug when page is temporally busy
On Fri, 9 Feb 2007 07:29:31 +0300 "Ananiev, Leonid I" <leonid.i.ananiev@intel.com> wrote:

> >From Leonid Ananiev
>
> Fix "Kernel BUG at fs/aio.c:509". Return EIOCBRETRY but not EIO if page
> is busy.
>
> Signed-off-by: Leonid Ananiev <leonid.i.ananiev@intel.com>
>
> "Kernel BUG at fs/aio.c:509"
> http://marc.theaimsgroup.com/?l=linux-kernel&m=117031052517746&w=2
> is present in 2.6.20 as well as 2.6.19.
> The investigation shows that the bug's panic occurs when aio_complete()
> is called with argument ret=EIO which is returned from
> invalidate_inode_pages2_range() because the page is temporally busy.
> Call Trace:
> [<ffffffff802573c3>] invalidate_inode_pages2_range+0x236/0x26b
> [<ffffffff802af77b>] ext3_direct_IO+0x16c/0x19e
> [<ffffffff802adc1d>] ext3_get_block+0x0/0xe2
> [<ffffffff802518c0>] generic_file_direct_IO+0xb9/0xcf
> [<ffffffff8025193d>] generic_file_direct_write+0x67/0x10e
> [<ffffffff80252308>] __generic_file_aio_write_nolock+0x2d6/0x3fe
> [<ffffffff802082c0>] __switch_to+0x26f/0x27e
> [<ffffffff8047b8e9>] thread_return+0x0/0xd8
> [<ffffffff80252497>] generic_file_aio_write+0x67/0xc7
> [<ffffffff802ab2cc>] ext3_file_write+0x0/0x8f
> [<ffffffff802ab2e2>] ext3_file_write+0x16/0x8f
> [<ffffffff802ab2cc>] ext3_file_write+0x0/0x8f
> [<ffffffff80283f61>] aio_rw_vect_retry+0x72/0x14f
> [<ffffffff80284ad9>] aio_run_iocb+0xe6/0x187
> [<ffffffff802853e2>] io_submit_one+0x296/0x2e3
> [<ffffffff80285979>] sys_io_submit+0x9b/0x108
> [<ffffffff80229b49>] default_wake_function+0x0/0xe
> [<ffffffff8020983e>] system_call+0x7e/0x83
>
> As a result aio_complete() is called while it should not be.
> When IO is finished aio_complete() is called once more
> and iocb->ki_users becomes negative.
>
> Taking into account aio.c lines in aio_run_iocb()
> if (ret != -EIOCBRETRY && ret != -EIOCBQUEUED) {
> aio_complete(iocb, ret, 0);
>
> proposed patch makes function invalidate_inode_pages2_range()
> to return EIOCBRETRY but not EIO if page is busy.
> The patch is tested on 2.6.20.
>
> --- linux-2.6.20/mm/truncate.c 2007-02-04 10:44:54.000000000 -0800
> +++ linux-2.6.20p/mm/truncate.c 2007-02-08 11:38:11.000000000 -0800
> @@ -366,7 +366,7 @@ static int do_launder_page(struct addres
> * Any pages which are found to be mapped into pagetables are unmapped
> prior to
> * invalidation.
> *
> - * Returns -EIO if any pages could not be invalidated.
> + * Returns -EIOCBRETRY if any pages could not be invalidated.
> */
> int invalidate_inode_pages2_range(struct address_space *mapping,
> pgoff_t start, pgoff_t end)
> @@ -423,7 +423,7 @@ int invalidate_inode_pages2_range(struct
> }
> ret = do_launder_page(mapping, page);
> if (ret == 0 &&
> !invalidate_complete_page2(mapping, page))
> - ret = -EIO;
> + ret = -EIOCBRETRY;
> unlock_page(page);
> }
> pagevec_release(&pvec);
> @@ -440,7 +440,7 @@ EXPORT_SYMBOL_GPL(invalidate_inode_pages
> * Any pages which are found to be mapped into pagetables are unmapped
> prior to
> * invalidation.
> *
> - * Returns -EIO if any pages could not be invalidated.
> + * Returns -EIOCBRETRY if any pages could not be invalidated.
> */
> int invalidate_inode_pages2(struct address_space *mapping)
> {

The patch is wildly wordwrapped and has had it tabs replaced with spaces.

invalidate_inode_pages2() has other callers. I suspect with this change
we'll end up leaking EIOCBRETRY back to userspace.

-
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