unimore/kernel-hacking-2024-linux-steffo
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kfifo: remove support for physically non-contiguous memory

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First, there is no such user. The only user of this interface is
caam_rng_fill_async() and that uses kfifo_alloc() -> kmalloc().

Second, the implementation does not allow anything else than direct
mapping and kmalloc() (due to virt_to_phys()), anyway.

Therefore, there is no point in having this dead (and complex) code in
the kernel.

Note the setup_sgl_buf() function now boils down to simple sg_set_buf().
That is called twice from setup_sgl() to take care of kfifo buffer
wrap-around.

setup_sgl_buf() will be extended shortly, so keeping it in place.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Stefani Seibold <stefani@seibold.net>
Link: https://lore.kernel.org/r/20240405060826.2521-5-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jiri Slaby (SUSE) 2024-04-05 08:08:15 +02:00 committed by Greg Kroah-Hartman
parent 4edd7e96a1
commit e9d9576de0
1 changed files with 5 additions and 33 deletions
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36
lib/kfifo.c
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@ -305,43 +305,15 @@ int __kfifo_to_user(struct __kfifo *fifo, void __user *to,
}
EXPORT_SYMBOL(__kfifo_to_user);
static int setup_sgl_buf(struct scatterlist *sgl, void *buf,
static unsigned int setup_sgl_buf(struct scatterlist *sgl, void *buf,
int nents, unsigned int len)
{
int n;
unsigned int l;
unsigned int off;
struct page *page;
if (!nents)
if (!nents || !len)
return 0;
if (!len)
return 0;
sg_set_buf(sgl, buf, len);
n = 0;
page = virt_to_page(buf);
off = offset_in_page(buf);
l = 0;
while (len >= l + PAGE_SIZE - off) {
struct page *npage;
l += PAGE_SIZE;
buf += PAGE_SIZE;
npage = virt_to_page(buf);
if (page_to_phys(page) != page_to_phys(npage) - l) {
sg_set_page(sgl, page, l - off, off);
sgl = sg_next(sgl);
if (++n == nents || sgl == NULL)
return n;
page = npage;
len -= l - off;
l = off = 0;
}
}
sg_set_page(sgl, page, len, off);
return n + 1;
return 1;
}
static unsigned int setup_sgl(struct __kfifo *fifo, struct scatterlist *sgl,