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In mb_unmapped_compress() we don't need mbuf structure to keep data,

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but we need buffer of MLEN bytes.  This isn't just a simplification,
but important fixup, because previous commit shrinked sizeof(struct
mbuf) down below MSIZE, and instantiating an mbuf on stack no longer
provides enough data.

Reviewed by:	gallatin
Differential Revision:	https://reviews.freebsd.org/D24598
This commit is contained in:
Gleb Smirnoff 2020-05-02 22:44:23 +00:00
parent 0c1032665c
commit 4c9f0f982f
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=360570
1 changed files with 4 additions and 8 deletions
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12
sys/kern/kern_mbuf.c
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@ -853,7 +853,7 @@ int
mb_unmapped_compress(struct mbuf *m)
{
volatile u_int *refcnt;
struct mbuf m_temp;
char buf[MLEN];
/*
* Assert that 'm' does not have a packet header. If 'm' had
@ -876,11 +876,7 @@ mb_unmapped_compress(struct mbuf *m)
if (*refcnt != 1)
return (EBUSY);
m_init(&m_temp, M_NOWAIT, MT_DATA, 0);
/* copy data out of old mbuf */
m_copydata(m, 0, m->m_len, mtod(&m_temp, char *));
m_temp.m_len = m->m_len;
m_copydata(m, 0, m->m_len, buf);
/* Free the backing pages. */
m->m_ext.ext_free(m);
@ -889,8 +885,8 @@ mb_unmapped_compress(struct mbuf *m)
m->m_flags &= ~(M_EXT | M_RDONLY | M_NOMAP);
m->m_data = m->m_dat;
/* copy data back into m */
m_copydata(&m_temp, 0, m_temp.m_len, mtod(m, char *));
/* Copy data back into m. */
bcopy(buf, mtod(m, char *), m->m_len);
return (0);
}