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null_blk: Zero-initialize read buffers in non-memory-backed mode 

This patch suppresses an uninteresting KMSAN complaint without affecting
performance of the null_blk driver if CONFIG_KMSAN is disabled.

Reported-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Tested-by: Alexander Potapenko <glider@google.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Damien Le Moal <damien.lemoal@wdc.com>
Cc: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Cc: Alexander Potapenko <glider@google.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Bart Van Assche 2020-05-18 21:07:37 -07:00 committed by Jens Axboe
parent 854b5f01dc
commit cecbc9ce80
1 changed files with 26 additions and 0 deletions
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26
drivers/block/null_blk_main.c
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@ -1250,8 +1250,34 @@ static inline blk_status_t null_handle_memory_backed(struct nullb_cmd *cmd,
return errno_to_blk_status(err);
}
static void nullb_zero_read_cmd_buffer(struct nullb_cmd *cmd)
{
struct nullb_device *dev = cmd->nq->dev;
struct bio *bio;
if (dev->memory_backed)
return;
if (dev->queue_mode == NULL_Q_BIO && bio_op(cmd->bio) == REQ_OP_READ) {
zero_fill_bio(cmd->bio);
} else if (req_op(cmd->rq) == REQ_OP_READ) {
__rq_for_each_bio(bio, cmd->rq)
zero_fill_bio(bio);
}
}
static inline void nullb_complete_cmd(struct nullb_cmd *cmd)
{
/*
* Since root privileges are required to configure the null_blk
* driver, it is fine that this driver does not initialize the
* data buffers of read commands. Zero-initialize these buffers
* anyway if KMSAN is enabled to prevent that KMSAN complains
* about null_blk not initializing read data buffers.
*/
if (IS_ENABLED(CONFIG_KMSAN))
nullb_zero_read_cmd_buffer(cmd);
/* Complete IO by inline, softirq or timer */
switch (cmd->nq->dev->irqmode) {
case NULL_IRQ_SOFTIRQ: