linux-kernel - Re: [PATCH 5/8] fs/ntfs3: Use kvmalloc instead of kmalloc(... __GFP

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Date: Sat, 23 Dec 2023 04:46:12 +0000
From: Matthew Wilcox <willy@...radead.org>
To: Konstantin Komarov <almaz.alexandrovich@...agon-software.com>
Cc: ntfs3@...ts.linux.dev,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 5/8] fs/ntfs3: Use kvmalloc instead of kmalloc(...
 __GFP_NOWARN)

On Mon, Jul 03, 2023 at 11:26:36AM +0400, Konstantin Komarov wrote:
> 
> Signed-off-by: Konstantin Komarov <almaz.alexandrovich@...agon-software.com>

So, um, why?  I mean, I know what kvmalloc does, but why do you want to
do it?  Also, this is missing changes from kfree() to kvfree() so if
you do end up falling back to vmalloc, you'll hit a bug in kfree().

> +++ b/fs/ntfs3/attrlist.c
> @@ -52,7 +52,8 @@ int ntfs_load_attr_list(struct ntfs_inode *ni, struct
> ATTRIB *attr)
> 
>      if (!attr->non_res) {
>          lsize = le32_to_cpu(attr->res.data_size);
> -        le = kmalloc(al_aligned(lsize), GFP_NOFS | __GFP_NOWARN);
> +        /* attr is resident: lsize < record_size (1K or 4K) */
> +        le = kvmalloc(al_aligned(lsize), GFP_KERNEL);
>          if (!le) {
>              err = -ENOMEM;
>              goto out;

This one should be paired with a kvfree in al_destroy(), I think.

> diff --git a/fs/ntfs3/bitmap.c b/fs/ntfs3/bitmap.c
> index 107e808e06ea..d66055e30aff 100644
> --- a/fs/ntfs3/bitmap.c
> +++ b/fs/ntfs3/bitmap.c
> @@ -659,7 +659,8 @@ int wnd_init(struct wnd_bitmap *wnd, struct super_block
> *sb, size_t nbits)
>          wnd->bits_last = wbits;
> 
>      wnd->free_bits =
> -        kcalloc(wnd->nwnd, sizeof(u16), GFP_NOFS | __GFP_NOWARN);
> +        kvmalloc_array(wnd->nwnd, sizeof(u16), GFP_KERNEL | __GFP_ZERO);
> +
>      if (!wnd->free_bits)
>          return -ENOMEM;
> 

This one with wnd_close() and of course later in wnd_init().

> diff --git a/fs/ntfs3/super.c b/fs/ntfs3/super.c
> index da739e509269..0034952b9ccd 100644
> --- a/fs/ntfs3/super.c
> +++ b/fs/ntfs3/super.c
> @@ -1373,7 +1373,7 @@ static int ntfs_fill_super(struct super_block *sb,
> struct fs_context *fc)
>      }
> 
>      bytes = inode->i_size;
> -    sbi->def_table = t = kmalloc(bytes, GFP_NOFS | __GFP_NOWARN);
> +    sbi->def_table = t = kvmalloc(bytes, GFP_KERNEL);
>      if (!t) {
>          err = -ENOMEM;
>          goto put_inode_out;

And this one with ntfs3_free_sbi()