On Fri, 2005-03-25 at 06:59, Badari Pulavarty wrote:
> Andrew,
>
> When I debugged the problem, the issue seems to be only for the last
> block of the file. Filesize is not multiple of 4K blocks. (say 17K).
> So, on the disk we have a 4K block for the last block. The test is
> trying to read 20K. Since we have a block on the disk, get_block()
> won't complain and we do the IO. Once the IO is done, we can truncate
> the result to match the filesize.
>
> I tried fixing the problem by limiting the IO submits to the size of
> the file - which became really ugly (since I have to adjust the
> iovec[]).
>
> Daniel McNeil wanted to take a stab at it. Dan what happend to the fix ?
>
> Thanks,
> Badari
I updated the patch to add an i_size element to the dio structure and
sample i_size during i/o submission. When i/o completes the result can
be truncated to match the file size without using i_size_read(), thus
the aio result now matches the number of bytes read to the end of file.
Here's the patch. It applies to 2.6.11 and the latest bk.
Daniel
--- linux-2.6.11.orig/fs/direct-io.c 2005-04-01 15:33:11.000000000 -0800
+++ linux-2.6.11/fs/direct-io.c 2005-03-31 16:59:15.000000000 -0800
@@ -66,6 +66,7 @@ struct dio {
struct bio *bio; /* bio under assembly */
struct inode *inode;
int rw;
+ ssize_t i_size; /* i_size when submitted */
int lock_type; /* doesn't change */
unsigned blkbits; /* doesn't change */
unsigned blkfactor; /* When we're using an alignment which
@@ -230,17 +231,29 @@ static void finished_one_bio(struct dio
spin_lock_irqsave(&dio->bio_lock, flags);
if (dio->bio_count == 1) {
if (dio->is_async) {
+ ssize_t transferred;
+ loff_t offset;
+
/*
* Last reference to the dio is going away.
* Drop spinlock and complete the DIO.
*/
spin_unlock_irqrestore(&dio->bio_lock, flags);
- dio_complete(dio, dio->block_in_file << dio->blkbits,
- dio->result);
+
+ /* Check for short read case */
+ transferred = dio->result;
+ offset = dio->iocb->ki_pos;
+
+ if ((dio->rw == READ) &&
+ ((offset + transferred) > dio->i_size))
+ transferred = dio->i_size - offset;
+
+ dio_complete(dio, offset, transferred);
+
/* Complete AIO later if falling back to buffered i/o */
if (dio->result == dio->size ||
((dio->rw == READ) && dio->result)) {
- aio_complete(dio->iocb, dio->result, 0);
+ aio_complete(dio->iocb, transferred, 0);
kfree(dio);
return;
} else {
@@ -951,6 +964,7 @@ direct_io_worker(int rw, struct kiocb *i
dio->page_errors = 0;
dio->result = 0;
dio->iocb = iocb;
+ dio->i_size = i_size_read(inode);
/*
* BIO completion state.
-
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