On Fri, Nov 30, 2012 at 4:10 PM, Boaz Harrosh <bharrosh@xxxxxxxxxxx> wrote:
> On 11/26/2012 04:49 PM, Idan Kedar wrote:
>> if ore_write() fails, we would unlock the pages of pcol, which is now
>> empty, rather than pcol_copy which owns the pages when ore_write() is
>> called. this means that no pages will actually be unlocked
>> (pcol.nr_pages == 0) and the writing process (more accurately, the
>> syncing process) will hang waiting for a writeback notification that
>> never comes.
>>
>> moreover, if ore_write() fails, pcol_free() is called for pcol, whereas
>> pcol_copy is the object owning the ore_io_state, thus leaking the
>> ore_io_state.
>>
>> Signed-off-by: Idan Kedar <idank@xxxxxxxxxx>
>
> Thanks Idan, good catch.
>
> I have simplified your patch a bit, see below. But basically it
> is all the same. Please check me out
>
>> ---
>> fs/exofs/inode.c | 7 ++++---
>> 1 files changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/exofs/inode.c b/fs/exofs/inode.c
>> index b561810..5106213 100644
>> --- a/fs/exofs/inode.c
>> +++ b/fs/exofs/inode.c
>> @@ -628,7 +628,7 @@ static int write_exec(struct page_collect *pcol)
>> {
>> struct exofs_i_info *oi = exofs_i(pcol->inode);
>> struct ore_io_state *ios;
>> - struct page_collect *pcol_copy = NULL;
>> + struct page_collect *pcol_copy = NULL, *active_pcol = pcol;
>> int ret;
>>
>> if (!pcol->pages)
>> @@ -658,6 +658,7 @@ static int write_exec(struct page_collect *pcol)
>>
>> /* pages ownership was passed to pcol_copy */
>> _pcol_reset(pcol);
>> + active_pcol = pcol_copy;
>>
>> ret = _maybe_not_all_in_one_io(ios, pcol_copy, pcol);
>> if (unlikely(ret))
>> @@ -676,8 +677,8 @@ static int write_exec(struct page_collect *pcol)
>> return 0;
>>
>> err:
>> - _unlock_pcol_pages(pcol, ret, WRITE);
>> - pcol_free(pcol);
>> + _unlock_pcol_pages(active_pcol, ret, WRITE);
>> + pcol_free(active_pcol);
>> kfree(pcol_copy);
>>
>> return ret;
>
> From: Idan Kedar <idank@xxxxxxxxxx>
> Subject: [PATCH] exofs: clean up the correct page collection on write error
>
> if ore_write() fails, we would unlock the pages of pcol, which is now
> empty, rather than pcol_copy which owns the pages when ore_write() is
> called. this means that no pages will actually be unlocked
> (pcol.nr_pages == 0) and the writing process (more accurately, the
> syncing process) will hang waiting for a writeback notification that
> never comes.
>
> moreover, if ore_write() fails, pcol_free() is called for pcol, whereas
> pcol_copy is the object owning the ore_io_state, thus leaking the
> ore_io_state.
>
> [Boaz]
> I have simplified Idan's original patch a bit, everything else still
> holds
>
> Signed-off-by: Idan Kedar <idank@xxxxxxxxxx>
> Signed-off-by: Boaz Harrosh <bharrosh@xxxxxxxxxxx>
> ---
> fs/exofs/inode.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/fs/exofs/inode.c b/fs/exofs/inode.c
> index 19dcc7b..8d82624 100644
> --- a/fs/exofs/inode.c
> +++ b/fs/exofs/inode.c
> @@ -676,8 +676,10 @@ static int write_exec(struct page_collect *pcol)
> return 0;
>
> err:
> - _unlock_pcol_pages(pcol, ret, WRITE);
> - pcol_free(pcol);
> + if (!pcol_copy) /* Failed before ownership transfer */
> + pcol_copy = pcol;
> + _unlock_pcol_pages(pcol_copy, ret, WRITE);
> + pcol_free(pcol_copy);
> kfree(pcol_copy);
>
> return ret;
> --
> 1.7.10.2.677.gb6bc67f
>
I started with that implementation, but it seemed less readable to me.
On Fri, Nov 30, 2012 at 4:15 PM, Boaz Harrosh <bharrosh@xxxxxxxxxxx> wrote:
> On 11/30/2012 04:10 PM, Boaz Harrosh wrote:
>
> I forgot to ask do you need this for stable?
>
> Boaz
nope.
--
idank
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