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From:   Andreas Dilger <adilger@dilger.ca>
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Subject: Re: [PATCH v3 1/4] kernfs: kvmalloc xattr value instead of kmalloc
Date:   Thu, 12 Mar 2020 15:09:09 -0600
In-Reply-To: <20200312200317.31736-2-dxu@dxuuu.xyz>
Cc:     cgroups@vger.kernel.org, tj@kernel.org, lizefan@huawei.com,
        hannes@cmpxchg.org, viro@zeniv.linux.org.uk, shakeelb@google.com,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        gregkh@linuxfoundation.org, kernel-team@fb.com
To:     Daniel Xu <dxu@dxuuu.xyz>
References: <20200312200317.31736-1-dxu@dxuuu.xyz>
 <20200312200317.31736-2-dxu@dxuuu.xyz>
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On Mar 12, 2020, at 2:03 PM, Daniel Xu <dxu@dxuuu.xyz> wrote:
>=20
> xattr values have a 64k maximum size. This can result in an order 4
> kmalloc request which can be difficult to fulfill. Since xattrs do not
> need physically contiguous memory, we can switch to kvmalloc and not
> have to worry about higher order allocations failing.
>=20
> Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>

Reviewed-by: Andreas Dilger <adilger@dilger.ca>

> ---
> fs/xattr.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>=20
> diff --git a/fs/xattr.c b/fs/xattr.c
> index 90dd78f0eb27..0d3c9b4d1914 100644
> --- a/fs/xattr.c
> +++ b/fs/xattr.c
> @@ -817,7 +817,7 @@ struct simple_xattr *simple_xattr_alloc(const void =
*value, size_t size)
> 	if (len < sizeof(*new_xattr))
> 		return NULL;
>=20
> -	new_xattr =3D kmalloc(len, GFP_KERNEL);
> +	new_xattr =3D kvmalloc(len, GFP_KERNEL);
> 	if (!new_xattr)
> 		return NULL;
>=20
> @@ -882,7 +882,7 @@ int simple_xattr_set(struct simple_xattrs *xattrs, =
const char *name,
>=20
> 		new_xattr->name =3D kstrdup(name, GFP_KERNEL);
> 		if (!new_xattr->name) {
> -			kfree(new_xattr);
> +			kvfree(new_xattr);
> 			return -ENOMEM;
> 		}
> 	}
> @@ -912,7 +912,7 @@ int simple_xattr_set(struct simple_xattrs *xattrs, =
const char *name,
> 	spin_unlock(&xattrs->lock);
> 	if (xattr) {
> 		kfree(xattr->name);
> -		kfree(xattr);
> +		kvfree(xattr);
> 	}
> 	return err;
>=20
> --
> 2.21.1
>=20


Cheers, Andreas


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