Re: [PATCH v2 1/2] vhost-scsi: use kvzalloc for vq array allocation

On 8/2/26 12:24 PM, Dongli Zhang wrote:
> vhost_scsi_open() allocates one "struct vhost_scsi_virtqueue" for each
> virtqueue. With large max_io_vqs values, this array can require a
> high-order contiguous allocation and trigger a page allocator warning.
> 
> hv# cat /sys/module/vhost_scsi/parameters/max_io_vqs
> 256
> 
> [  766.075787] ------------[ cut here ]------------
> [  766.077030] WARNING: mm/page_alloc.c:5280 at __alloc_frozen_pages_noprof+0x32c/0x15c0, CPU#23: qemu-system-x86/5964
> ... ...
> [  766.080351] RIP: 0010:__alloc_frozen_pages_noprof+0x32c/0x15c0
> ... ...
> [  766.085813] Call Trace:
> [  766.085969]  <TASK>
> [  766.086098]  ? srso_alias_return_thunk+0x5/0xfbef5
> [  766.086365]  ? context_struct_compute_av+0x38a/0x4b0
> [  766.086652]  alloc_pages_mpol+0x9f/0x170
> [  766.086883]  ___kmalloc_large_node+0xb6/0xd0
> [  766.087124]  ? srso_alias_return_thunk+0x5/0xfbef5
> [  766.087389]  __kmalloc_large_node_noprof+0x18/0xa0
> [  766.087655]  __kmalloc_noprof+0x3a0/0x440
> [  766.087877]  ? vhost_scsi_open+0xcb/0x2d0 [vhost_scsi]
> [  766.088162]  vhost_scsi_open+0xcb/0x2d0 [vhost_scsi]
> [  766.088449]  misc_open+0x123/0x160
> [  766.088679]  chrdev_open+0xb1/0x230
> [  766.088885]  ? __pfx_chrdev_open+0x10/0x10
> [  766.089157]  do_dentry_open+0x11a/0x470
> [  766.089389]  vfs_open+0x29/0xf0
> [  766.089596]  path_openat+0x7c0/0x1100
> [  766.089821]  do_file_open+0xdd/0x190
> [  766.090032]  ? srso_alias_return_thunk+0x5/0xfbef5
> [  766.090332]  do_sys_openat2+0x7e/0x100
> [  766.090601]  __x64_sys_openat+0x51/0xa0
> [  766.090857]  do_syscall_64+0xfe/0x590
> [  766.091087]  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> [  766.091411] RIP: 0033:0x7f9525a11fa6
> 
> The array does not require physical contiguity, so allocate it with
> kvzalloc_objs() and free it with kvfree().
> 
> Signed-off-by: Dongli Zhang <[email protected]>
Reviewed-by: Mike Christie <[email protected]>