Dave Chinner <david@xxxxxxxxxxxxx> writes:
> +struct dio_zero_block {
> + struct list_head dio_list; /* list of io in progress */
> + sector_t zero_block; /* block being zeroed */
> + struct dio *dio; /* owner dio */
> + wait_queue_head_t wq; /* New IO block here */
New IOs block here, or new IO blocks here?
> +/*
> + * Add a filesystem block to the list of blocks we are tracking.
> + */
> +static void
> +dio_start_zero_block(struct dio *dio, sector_t zero_block)
> +{
> + struct dio_zero_block *zb;
> +
> + zb = kmalloc(sizeof(*zb), GFP_NOIO);
> + if (!zb)
> + return;
> + INIT_LIST_HEAD(&zb->dio_list);
> + init_waitqueue_head(&zb->wq);
> + zb->zero_block = zero_block;
> + zb->dio = dio;
> + atomic_set(&zb->ref, 1);
> +
> + spin_lock(&dio_zero_block_lock);
> + list_add(&zb->dio_list, &dio_zero_block_list);
> + spin_unlock(&dio_zero_block_lock);
What protects from two processes getting here at the same time, and
hence adding the same block to the list? i_mutex?
> @@ -1210,6 +1343,13 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
> */
> memset(dio, 0, offsetof(struct dio, pages));
>
> + /*
> + * zero_blocks need to initialised to largeÑt value to avoid
^ be
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