Re: [PATCH] btrfs: use kvcalloc in btrfs_get_dev_zone_info

[Damien Le Moal <damien.lemoal@opensource.wdc.com>]

On 11/20/22 21:43, Christoph Hellwig wrote:
> Otherwise the kernel memory allocator seems to be unhappy about failing
> order 6 allocations for the zones array, that cause 100% reproducible
> mount failures in my qemu setup:
> 
> [   26.078981] mount: page allocation failure: order:6, mode:0x40dc0(GFP_KERNEL|__GFP_COMP|__GFP_ZERO), nodemask=(null)
> [   26.079741] CPU: 0 PID: 2965 Comm: mount Not tainted 6.1.0-rc5+ #185
> [   26.080181] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
> [   26.080950] Call Trace:
> [   26.081132]  <TASK>
> [   26.081291]  dump_stack_lvl+0x56/0x6f
> [   26.081554]  warn_alloc+0x117/0x140
> [   26.081808]  ? __alloc_pages_direct_compact+0x1b5/0x300
> [   26.082174]  __alloc_pages_slowpath.constprop.0+0xd0e/0xde0
> [   26.082569]  __alloc_pages+0x32a/0x340
> [   26.082836]  __kmalloc_large_node+0x4d/0xa0
> [   26.083133]  ? trace_kmalloc+0x29/0xd0
> [   26.083399]  kmalloc_large+0x14/0x60
> [   26.083654]  btrfs_get_dev_zone_info+0x1b9/0xc00
> [   26.083980]  ? _raw_spin_unlock_irqrestore+0x28/0x50
> [   26.084328]  btrfs_get_dev_zone_info_all_devices+0x54/0x80
> [   26.084708]  open_ctree+0xed4/0x1654
> [   26.084974]  btrfs_mount_root.cold+0x12/0xde
> [   26.085288]  ? lock_is_held_type+0xe2/0x140
> [   26.085603]  legacy_get_tree+0x28/0x50
> [   26.085876]  vfs_get_tree+0x1d/0xb0
> [   26.086139]  vfs_kern_mount.part.0+0x6c/0xb0
> [   26.086456]  btrfs_mount+0x118/0x3a0
> [   26.086728]  ? lock_is_held_type+0xe2/0x140
> [   26.087043]  legacy_get_tree+0x28/0x50
> [   26.087323]  vfs_get_tree+0x1d/0xb0
> [   26.087587]  path_mount+0x2ba/0xbe0
> [   26.087850]  ? _raw_spin_unlock_irqrestore+0x38/0x50
> [   26.088217]  __x64_sys_mount+0xfe/0x140
> [   26.088506]  do_syscall_64+0x35/0x80
> [   26.088776]  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Looks good.
This likely needs a fixes tag though.

Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>

> ---
>  fs/btrfs/zoned.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
> index 2218b33dac568..a759668477bb2 100644
> --- a/fs/btrfs/zoned.c
> +++ b/fs/btrfs/zoned.c
> @@ -468,7 +468,7 @@ int btrfs_get_dev_zone_info(struct btrfs_device *device, bool populate_cache)
>  		goto out;
>  	}
>  
> -	zones = kcalloc(BTRFS_REPORT_NR_ZONES, sizeof(struct blk_zone), GFP_KERNEL);
> +	zones = kvcalloc(BTRFS_REPORT_NR_ZONES, sizeof(struct blk_zone), GFP_KERNEL);
>  	if (!zones) {
>  		ret = -ENOMEM;
>  		goto out;
> @@ -587,7 +587,7 @@ int btrfs_get_dev_zone_info(struct btrfs_device *device, bool populate_cache)
>  	}
>  
>  
> -	kfree(zones);
> +	kvfree(zones);
>  
>  	switch (bdev_zoned_model(bdev)) {
>  	case BLK_ZONED_HM:
> @@ -619,7 +619,7 @@ int btrfs_get_dev_zone_info(struct btrfs_device *device, bool populate_cache)
>  	return 0;
>  
>  out:
> -	kfree(zones);
> +	kvfree(zones);
>  out_free_zone_info:
>  	btrfs_destroy_dev_zone_info(device);
>  

-- 
Damien Le Moal
Western Digital Research