Author: np
Date: Mon Oct 24 19:09:56 2016
New Revision: 307876
URL: https://svnweb.freebsd.org/changeset/base/307876
Log:
cxgbe(4): Fix bug in the calculation of the number of physically
contiguous regions in an mbuf chain.
If the payload of an mbuf ends at a page boundary count_mbuf_nsegs would
incorrectly consider the next mbuf's payload physically contiguous based
solely on a KVA comparison.
MFC after: 1 week
Sponsored by: Chelsio Communications
Modified:
head/sys/dev/cxgbe/t4_sge.c
Modified: head/sys/dev/cxgbe/t4_sge.c
==============================================================================
--- head/sys/dev/cxgbe/t4_sge.c Mon Oct 24 18:27:24 2016 (r307875)
+++ head/sys/dev/cxgbe/t4_sge.c Mon Oct 24 19:09:56 2016 (r307876)
@@ -2110,24 +2110,6 @@ m_advance(struct mbuf **pm, int *poffset
return ((void *)p);
}
-static inline int
-same_paddr(char *a, char *b)
-{
-
- if (a == b)
- return (1);
- else if (a != NULL && b != NULL) {
- vm_offset_t x = (vm_offset_t)a;
- vm_offset_t y = (vm_offset_t)b;
-
- if ((x & PAGE_MASK) == (y & PAGE_MASK) &&
- pmap_kextract(x) == pmap_kextract(y))
- return (1);
- }
-
- return (0);
-}
-
/*
* Can deal with empty mbufs in the chain that have m_len = 0, but the chain
* must have at least one mbuf that's not empty.
@@ -2135,24 +2117,25 @@ same_paddr(char *a, char *b)
static inline int
count_mbuf_nsegs(struct mbuf *m)
{
- char *prev_end, *start;
+ vm_paddr_t lastb, next;
+ vm_offset_t va;
int len, nsegs;
MPASS(m != NULL);
nsegs = 0;
- prev_end = NULL;
+ lastb = 0;
for (; m; m = m->m_next) {
len = m->m_len;
if (__predict_false(len == 0))
continue;
- start = mtod(m, char *);
-
- nsegs += sglist_count(start, len);
- if (same_paddr(prev_end, start))
+ va = mtod(m, vm_offset_t);
+ next = pmap_kextract(va);
+ nsegs += sglist_count(m->m_data, len);
+ if (lastb + 1 == next)
nsegs--;
- prev_end = start + len;
+ lastb = pmap_kextract(va + len - 1);
}
MPASS(nsegs > 0);
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