On 1/31/11 6:15 PM, Curt Wohlgemuth wrote:
> Sorry: I forgot to mention that I tested this on 2.6.37 under KVM
> with the postgresql script specified by Ted in
> 1449032be17abb69116dbc393f67ceb8bd034f92 -- without this commit, and
> hence by default using the multiblock writepages submittal code.
>
> Without the patch, I'd hit the corruption problem about 50-70% of the
> time. With the patch, I executed the script > 100 times with no
> corruption seen.
Can you resubmit with a changelog that indicates it's actually a corruption
fix? Maybe even in the summary. That is important information to have
for the commit...
-Eric
> Curt
>
> On Mon, Jan 31, 2011 at 12:44 PM, Curt Wohlgemuth <curtw@xxxxxxxxxx> wrote:
>> The ext4 code path to bundle multiple pages for writeback in
>> ext4_bio_write_page() had a bug: we should be clearing buffer head dirty
>> flags before we submit the bio, not in the completion routine.
>>
>> Also don't deference the bio in ext4_end_bio() after the bio_put() call.
>>
>> (I also added a blank line in ext4_bio_write_page(), 'cause my eyes
>> constantly confused the complex 'for' conditions from the first statement
>> in the block.)
>>
>> Signed-off-by: Curt Wohlgemuth <curtw@xxxxxxxxxx>
>>
>> ---
>>
>> diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
>> index 6e0e99b..c3d490f 100644
>> --- a/fs/ext4/page-io.c
>> +++ b/fs/ext4/page-io.c
>> @@ -193,6 +193,7 @@ static void ext4_end_bio(struct bio *bio, int error)
>> struct inode *inode;
>> unsigned long flags;
>> int i;
>> + sector_t bi_sector = bio->bi_sector;
>>
>> BUG_ON(!io_end);
>> bio->bi_private = NULL;
>> @@ -210,9 +211,7 @@ static void ext4_end_bio(struct bio *bio, int error)
>> if (error)
>> SetPageError(page);
>> BUG_ON(!head);
>> - if (head->b_size == PAGE_CACHE_SIZE)
>> - clear_buffer_dirty(head);
>> - else {
>> + if (head->b_size != PAGE_CACHE_SIZE) {
>> loff_t offset;
>> loff_t io_end_offset = io_end->offset + io_end->size;
>>
>> @@ -224,7 +223,6 @@ static void ext4_end_bio(struct bio *bio, int error)
>> if (error)
>> buffer_io_error(bh);
>>
>> - clear_buffer_dirty(bh);
>> }
>> if (buffer_delay(bh))
>> partial_write = 1;
>> @@ -260,7 +258,7 @@ static void ext4_end_bio(struct bio *bio, int error)
>> (unsigned long long) io_end->offset,
>> (long) io_end->size,
>> (unsigned long long)
>> - bio->bi_sector >> (inode->i_blkbits - 9));
>> + bi_sector >> (inode->i_blkbits - 9));
>> }
>>
>> /* Add the io_end to per-inode completed io list*/
>> @@ -383,6 +381,7 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
>>
>> blocksize = 1 << inode->i_blkbits;
>>
>> + BUG_ON(!PageLocked(page));
>> BUG_ON(PageWriteback(page));
>> set_page_writeback(page);
>> ClearPageError(page);
>> @@ -400,12 +399,14 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
>> for (bh = head = page_buffers(page), block_start = 0;
>> bh != head || !block_start;
>> block_start = block_end, bh = bh->b_this_page) {
>> +
>> block_end = block_start + blocksize;
>> if (block_start >= len) {
>> clear_buffer_dirty(bh);
>> set_buffer_uptodate(bh);
>> continue;
>> }
>> + clear_buffer_dirty(bh);
>> ret = io_submit_add_bh(io, io_page, inode, wbc, bh);
>> if (ret) {
>> /*
>>
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