On 26/11/18 2:12 PM, Boris Brezillon wrote:
Hi Jagan,
On Thu, 22 Nov 2018 09:40:56 +0100 Boris Brezillon boris.brezillon@bootlin.com wrote:
/** Setting mtd->priv to NULL is the best we can do. Thanks to that,* the MTD layer can still call mtd hooks without risking a* use-after-free bug. Still, things should be fixed to prevent the* spi_flash object from being destroyed when del_mtd_device() fails.*/sf_mtd_info.priv = NULL;printf("Failed to unregister MTD %s and the spi_flash object is going away: you're in deep trouble!",sf_mtd_info.name);Why do we need this print?
Yes we do, just to keep the user informed that something bad happened and its spi-flash is no longer usable (at least through the MTD layer).
can't we do the same thing in MTD core itself, so-that it can be generic for all flash objects.
del_mtd_device() can fail, so it's the caller responsibility to decide what to do when that happens. Some users will propagate the error to the upper layer and maybe cancel the device removal (AFAICT, driver->remove() can return an error, not sure what happens in this case though). For others, like spi-flash, the device will go away, and all subsequent accesses will fail.
I'm about to send a new version fixing the problem I mentioned in patch 3, but before doing that, I'd like to know if my answer convinced you or if you'd still prefer this message to go away (or be placed in mtdcore/mtdpart.c).
I'm thinking of having the message still in MTD by showing which interface it would belongs, along with the details.