Re: [GIT PULL] Modules changes for v6.7-rc1

[Andrea Righi <andrea.righi@canonical.com>]

On Thu, Nov 02, 2023 at 08:29:17AM +0100, Andrea Righi wrote:
> On Wed, Nov 01, 2023 at 09:21:09PM -1000, Linus Torvalds wrote:
> > On Wed, 1 Nov 2023 at 21:02, Linus Torvalds
> > <torvalds@linux-foundation.org> wrote:
> > >
> > > kmalloc() isn't just about "use physically contiguous allocations".
> > > It's also more memory-efficient, and a *lot* faster than vmalloc(),
> > > which has to play VM tricks.
> > 
> > I've pulled this, but I think you should do something like the
> > attached (UNTESTED!) patch.
> > 
> >                 Linus
> 
> Looks good to me, I'll give it a try ASAP.
> 
> -Andrea

Just tested this both with zstd and gzip module compression, all good.

You can add my:

Tested-by: Andrea Righi <andrea.righi@canonical.com>

Or if you need a proper paperwork:

--

From: Andrea Righi <andrea.righi@canonical.com>
Subject: [PATCH] module/decompress: use kvmalloc() consistently

We consistently switched from kmalloc() to vmalloc() in module
decompression to prevent potential memory allocation failures with large
modules, however vmalloc() is not as memory-efficient and fast as
kmalloc().

Since we don't know in general the size of the workspace required by the
decompression algorithm, it is more reasonable to use kvmalloc()
consistently, also considering that we don't have special memory
requirements here.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Tested-by: Andrea Righi <andrea.righi@canonical.com>
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
---
 kernel/module/decompress.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/module/decompress.c b/kernel/module/decompress.c
index 4156d59be440..474e68f0f063 100644
--- a/kernel/module/decompress.c
+++ b/kernel/module/decompress.c
@@ -100,7 +100,7 @@ static ssize_t module_gzip_decompress(struct load_info *info,
 	s.next_in = buf + gzip_hdr_len;
 	s.avail_in = size - gzip_hdr_len;
 
-	s.workspace = vmalloc(zlib_inflate_workspacesize());
+	s.workspace = kvmalloc(zlib_inflate_workspacesize(), GFP_KERNEL);
 	if (!s.workspace)
 		return -ENOMEM;
 
@@ -138,7 +138,7 @@ static ssize_t module_gzip_decompress(struct load_info *info,
 out_inflate_end:
 	zlib_inflateEnd(&s);
 out:
-	vfree(s.workspace);
+	kvfree(s.workspace);
 	return retval;
 }
 #elif defined(CONFIG_MODULE_COMPRESS_XZ)
@@ -241,7 +241,7 @@ static ssize_t module_zstd_decompress(struct load_info *info,
 	}
 
 	wksp_size = zstd_dstream_workspace_bound(header.windowSize);
-	wksp = vmalloc(wksp_size);
+	wksp = kvmalloc(wksp_size, GFP_KERNEL);
 	if (!wksp) {
 		retval = -ENOMEM;
 		goto out;
@@ -284,7 +284,7 @@ static ssize_t module_zstd_decompress(struct load_info *info,
 	retval = new_size;
 
  out:
-	vfree(wksp);
+	kvfree(wksp);
 	return retval;
 }
 #else
-- 
2.40.1