On 15/05/2020 10:50, Chris Hofstaedtler wrote: > * Johannes Thumshirn <johannes.thumshirn@xxxxxxx> [200515 10:41]: >> If a user submits a zone management ioctl from user-space, like a zone >> reset and a file-system (like zonefs or f2fs) is mounted on the zoned >> block device, the zone will get reset and the file-system's cached value >> of the zone's write-pointer becomes invalid. >> >> Subsequent writes to this zone from the file-system will result in >> unaligned writes and the drive will error out. > > "error out" meaning what exactly? The drive will report an Unaligned Write error. > >> Open the block device file in exclusive mode for submitting these ioctls. >> If a file-system is mounted the kernel will return -EBUSY and we can't >> continue issuing the ioctl. > > Isn't this something the kernel should enforce, then? I did a patch for the kernel yesterday [1] enforcing this limitation, but as Damien said it's SYS_CAP_ADMIN and with great power comes great responsibility. We're also allowing other raw block device accesses on block devices. [1] https://lore.kernel.org/linux-block/BY5PR04MB69006DE86D1050620B5EDAA4E7BD0@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ > What's to stop anybody from calling the ioctl from another tool, > without using O_EXCL? Nothing, but still we don't need to make one's life hard by letting blkzone go havoc with FS internal caching. If another tool does zone resets, it's up to them to check for mounted block devices.
