diff options
| author | Michael Kelley <mhklinux@outlook.com> | 2024-10-02 20:53:32 -0700 |
|---|---|---|
| committer | Martin K. Petersen <martin.petersen@oracle.com> | 2024-12-09 21:57:52 -0500 |
| commit | 6cb7063feb2eff2e52dc9624b2193a1f4cad69bf (patch) | |
| tree | 9641d10e6b5873141baf4cf26ae3940b80564056 | |
| parent | bd55f56188caf170d6dbdc04638159bd91d8401b (diff) | |
scsi: storvsc: Don't assume cpu_possible_mask is dense
Current code allocates the stor_chns array with size num_possible_cpus().
This code assumes cpu_possible_mask is dense, which is not true in the
general case per [1]. If cpu_possible_mask is sparse, the array might be
indexed by a value beyond the size of the array.
However, the configurations that Hyper-V provides to guest VMs on x86 and
ARM64 hardware, in combination with how architecture specific code assigns
Linux CPU numbers, *does* always produce a dense cpu_possible_mask. So the
dense assumption is not currently causing failures. But for robustness
against future changes in how cpu_possible_mask is populated, update the
code to no longer assume dense.
The correct approach is to allocate and initialize the array using size
"nr_cpu_ids". While this leaves unused array entries corresponding to holes
in cpu_possible_mask, the holes are assumed to be minimal and hence the
amount of memory wasted by unused entries is minimal.
[1] https://lore.kernel.org/lkml/SN6PR02MB4157210CC36B2593F8572E5ED4692@SN6PR02MB4157.namprd02.prod.outlook.com/
Signed-off-by: Michael Kelley <mhklinux@outlook.com>
Link: https://lore.kernel.org/r/20241003035333.49261-5-mhklinux@outlook.com
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
| -rw-r--r-- | drivers/scsi/storvsc_drv.c | 13 |
1 files changed, 6 insertions, 7 deletions
diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c index eab32abf1f49..5e3727e432d5 100644 --- a/drivers/scsi/storvsc_drv.c +++ b/drivers/scsi/storvsc_drv.c @@ -915,14 +915,13 @@ static int storvsc_channel_init(struct hv_device *device, bool is_fc) /* * Allocate state to manage the sub-channels. - * We allocate an array based on the numbers of possible CPUs - * (Hyper-V does not support cpu online/offline). - * This Array will be sparseley populated with unique - * channels - primary + sub-channels. - * We will however populate all the slots to evenly distribute - * the load. + * We allocate an array based on the number of CPU ids. This array + * is initially sparsely populated for the CPUs assigned to channels: + * primary + sub-channels. As I/Os are initiated by different CPUs, + * the slots for all online CPUs are populated to evenly distribute + * the load across all channels. */ - stor_device->stor_chns = kcalloc(num_possible_cpus(), sizeof(void *), + stor_device->stor_chns = kcalloc(nr_cpu_ids, sizeof(void *), GFP_KERNEL); if (stor_device->stor_chns == NULL) return -ENOMEM; |