From: "jaeyuel.im" <[email protected]> The current implementation of dm_init_init() uses early_lookup_bdev() to wait for the device node to appear. However, early_lookup_bdev() only verifies that the device node exists and returns the dev_t. It does not guarantee that the underlying block device structure is fully initialized and ready for I/O operations or to be opened.
On certain platforms (e.g., embedded systems with specific storage drivers), this can lead to a race condition where dm_early_create() attempts to open the device immediately after early_lookup_bdev() returns, but fails because the device is not yet fully ready. This results in boot failures as the mapped device cannot be created. This patch adds an additional check using blkdev_get_no_open() after early_lookup_bdev() returns. This ensures that the struct block_device is actually available and the device is ready to be opened, effectively preventing the race condition. Changes in v2: - Pass autoload parameter for new blkdev_get_no_open() Signed-off-by: jaeyuel.im <[email protected]> --- drivers/md/dm-init.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/drivers/md/dm-init.c b/drivers/md/dm-init.c index b37bbe762500..b3905e094ffc 100644 --- a/drivers/md/dm-init.c +++ b/drivers/md/dm-init.c @@ -296,10 +296,24 @@ static int __init dm_init_init(void) for (i = 0; i < ARRAY_SIZE(waitfor); i++) { if (waitfor[i]) { dev_t dev; + struct block_device *bdev; DMINFO("waiting for device %s ...", waitfor[i]); while (early_lookup_bdev(waitfor[i], &dev)) fsleep(5000); + + /* + * early_lookup_bdev() only checks if the device node exists and + * returns the dev_t. It does not guarantee that the underlying + * block device is fully initialized and ready to be opened. On + * some platforms, this can lead to a race condition where + * dm_early_create() fails because the device is not yet ready. + * Ensure the block device is truly available by attempting to + * get it. + */ + while (!(bdev = blkdev_get_no_open(dev, false))) + fsleep(5000); + blkdev_put_no_open(bdev); } } -- 2.34.1
