Fabian-Gruenbichler c0aab8b8f9 zvols: prevent overflow of minor device numbers ... currently, the linux kernel allows 2^20 minor devices per major device number. ZFS reserves blocks of 2^4 minors per zvol: 1 for the zvol itself, the other 15 for the first partitions of that zvol. as a result, only 2^16 such blocks are available for use. there are no checks in place to avoid overflowing into the major device number when more than 2^16 zvols are allocated (with volmode=dev or default). instead of ignoring this limit, which comes with all sorts of weird knock-on effects, detect this situation and simply fail allocating the zvol block device early on. without this safeguard, the kernel will reject the attempt to create an already existing block device, but ZFS doesn't handle this error and gets confused about which zvol occupies which minor slot, potentially resulting in kernel NULL derefs and other issues later on. Reviewed-by: Tony Hutter <hutter2@llnl.gov> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com> Closes #16006		2024-03-29 14:37:40 -07:00
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spl	Linux: Cleanup taskq threads spawn/exit	2024-02-13 11:15:16 -08:00
zfs	zvols: prevent overflow of minor device numbers	2024-03-29 14:37:40 -07:00