svn commit: r196417 - in head: share/man/man9 sys/kern
John Baldwin
jhb at FreeBSD.org
Fri Aug 21 02:59:08 UTC 2009
Author: jhb
Date: Fri Aug 21 02:59:07 2009
New Revision: 196417
URL: http://svn.freebsd.org/changeset/base/196417
Log:
This patch fixes two bugs in sglist(9) and improves robustness of the API via
better semantics if a request to append an address range to an existing list
fails.
- When cloning an sglist, properly set the length in the new sglist instead of
leaving the new list empty.
- Properly compute the amount of data added to an sglist via
_sglist_append_buf(). This allows sglist_consume_uio() to properly update
uio_resid.
- When a request to append an address range to a scatter/gather list fails,
restore the sglist to the state it had at the start of the function call
instead of resetting it to an empty list.
Requested by: np (3)
Approved by: re (kib)
Modified:
head/share/man/man9/sglist.9
head/sys/kern/subr_sglist.c
Modified: head/share/man/man9/sglist.9
==============================================================================
--- head/share/man/man9/sglist.9 Fri Aug 21 01:12:06 2009 (r196416)
+++ head/share/man/man9/sglist.9 Fri Aug 21 02:59:07 2009 (r196417)
@@ -191,6 +191,8 @@ Specifically, the
family of routines can be used to append the physical address ranges described
by an object to the end of a scatter/gather list.
All of these routines return 0 on success or an error on failure.
+If a request to append an address range to a scatter/gather list fails,
+the scatter/gather list will remain unchanged.
.Pp
The
.Nm sglist_append
@@ -445,6 +447,7 @@ There are not enough available segments
to append the physical address ranges from
.Fa second .
.El
+.Pp
The
.Nm sglist_slice
function returns the following errors on failure:
@@ -470,6 +473,7 @@ list in
.Fa *slice
to describe the requested physical address ranges.
.El
+.Pp
The
.Nm sglist_split
function returns the following errors on failure:
Modified: head/sys/kern/subr_sglist.c
==============================================================================
--- head/sys/kern/subr_sglist.c Fri Aug 21 01:12:06 2009 (r196416)
+++ head/sys/kern/subr_sglist.c Fri Aug 21 02:59:07 2009 (r196417)
@@ -48,6 +48,32 @@ __FBSDID("$FreeBSD$");
static MALLOC_DEFINE(M_SGLIST, "sglist", "scatter/gather lists");
/*
+ * Convenience macros to save the state of an sglist so it can be restored
+ * if an append attempt fails. Since sglist's only grow we only need to
+ * save the current count of segments and the length of the ending segment.
+ * Earlier segments will not be changed by an append, and the only change
+ * that can occur to the ending segment is that it can be extended.
+ */
+struct sgsave {
+ u_short sg_nseg;
+ size_t ss_len;
+};
+
+#define SGLIST_SAVE(sg, sgsave) do { \
+ (sgsave).sg_nseg = (sg)->sg_nseg; \
+ if ((sgsave).sg_nseg > 0) \
+ (sgsave).ss_len = (sg)->sg_segs[(sgsave).sg_nseg - 1].ss_len; \
+ else \
+ (sgsave).ss_len = 0; \
+} while (0)
+
+#define SGLIST_RESTORE(sg, sgsave) do { \
+ (sg)->sg_nseg = (sgsave).sg_nseg; \
+ if ((sgsave).sg_nseg > 0) \
+ (sg)->sg_segs[(sgsave).sg_nseg - 1].ss_len = (sgsave).ss_len; \
+} while (0)
+
+/*
* Append a single (paddr, len) to a sglist. sg is the list and ss is
* the current segment in the list. If we run out of segments then
* EFBIG will be returned.
@@ -62,10 +88,8 @@ _sglist_append_range(struct sglist *sg,
if (ss->ss_paddr + ss->ss_len == paddr)
ss->ss_len += len;
else {
- if (sg->sg_nseg == sg->sg_maxseg) {
- sg->sg_nseg = 0;
+ if (sg->sg_nseg == sg->sg_maxseg)
return (EFBIG);
- }
ss++;
ss->ss_paddr = paddr;
ss->ss_len = len;
@@ -107,26 +131,33 @@ _sglist_append_buf(struct sglist *sg, vo
ss->ss_paddr = paddr;
ss->ss_len = seglen;
sg->sg_nseg = 1;
- error = 0;
} else {
ss = &sg->sg_segs[sg->sg_nseg - 1];
error = _sglist_append_range(sg, &ss, paddr, seglen);
+ if (error)
+ return (error);
}
+ vaddr += seglen;
+ len -= seglen;
+ if (donep)
+ *donep += seglen;
- while (error == 0 && len > seglen) {
- vaddr += seglen;
- len -= seglen;
- if (donep)
- *donep += seglen;
+ while (len > 0) {
seglen = MIN(len, PAGE_SIZE);
if (pmap != NULL)
paddr = pmap_extract(pmap, vaddr);
else
paddr = pmap_kextract(vaddr);
error = _sglist_append_range(sg, &ss, paddr, seglen);
+ if (error)
+ return (error);
+ vaddr += seglen;
+ len -= seglen;
+ if (donep)
+ *donep += seglen;
}
- return (error);
+ return (0);
}
/*
@@ -195,10 +226,16 @@ sglist_free(struct sglist *sg)
int
sglist_append(struct sglist *sg, void *buf, size_t len)
{
+ struct sgsave save;
+ int error;
if (sg->sg_maxseg == 0)
return (EINVAL);
- return (_sglist_append_buf(sg, buf, len, NULL, NULL));
+ SGLIST_SAVE(sg, save);
+ error = _sglist_append_buf(sg, buf, len, NULL, NULL);
+ if (error)
+ SGLIST_RESTORE(sg, save);
+ return (error);
}
/*
@@ -209,6 +246,8 @@ int
sglist_append_phys(struct sglist *sg, vm_paddr_t paddr, size_t len)
{
struct sglist_seg *ss;
+ struct sgsave save;
+ int error;
if (sg->sg_maxseg == 0)
return (EINVAL);
@@ -222,7 +261,11 @@ sglist_append_phys(struct sglist *sg, vm
return (0);
}
ss = &sg->sg_segs[sg->sg_nseg - 1];
- return (_sglist_append_range(sg, &ss, paddr, len));
+ SGLIST_SAVE(sg, save);
+ error = _sglist_append_range(sg, &ss, paddr, len);
+ if (error)
+ SGLIST_RESTORE(sg, save);
+ return (error);
}
/*
@@ -233,6 +276,7 @@ sglist_append_phys(struct sglist *sg, vm
int
sglist_append_mbuf(struct sglist *sg, struct mbuf *m0)
{
+ struct sgsave save;
struct mbuf *m;
int error;
@@ -240,11 +284,14 @@ sglist_append_mbuf(struct sglist *sg, st
return (EINVAL);
error = 0;
+ SGLIST_SAVE(sg, save);
for (m = m0; m != NULL; m = m->m_next) {
if (m->m_len > 0) {
error = sglist_append(sg, m->m_data, m->m_len);
- if (error)
+ if (error) {
+ SGLIST_RESTORE(sg, save);
return (error);
+ }
}
}
return (0);
@@ -258,11 +305,17 @@ sglist_append_mbuf(struct sglist *sg, st
int
sglist_append_user(struct sglist *sg, void *buf, size_t len, struct thread *td)
{
+ struct sgsave save;
+ int error;
if (sg->sg_maxseg == 0)
return (EINVAL);
- return (_sglist_append_buf(sg, buf, len,
- vmspace_pmap(td->td_proc->p_vmspace), NULL));
+ SGLIST_SAVE(sg, save);
+ error = _sglist_append_buf(sg, buf, len,
+ vmspace_pmap(td->td_proc->p_vmspace), NULL);
+ if (error)
+ SGLIST_RESTORE(sg, save);
+ return (error);
}
/*
@@ -274,6 +327,7 @@ int
sglist_append_uio(struct sglist *sg, struct uio *uio)
{
struct iovec *iov;
+ struct sgsave save;
size_t resid, minlen;
pmap_t pmap;
int error, i;
@@ -292,6 +346,7 @@ sglist_append_uio(struct sglist *sg, str
pmap = NULL;
error = 0;
+ SGLIST_SAVE(sg, save);
for (i = 0; i < uio->uio_iovcnt && resid != 0; i++) {
/*
* Now at the first iovec to load. Load each iovec
@@ -301,8 +356,10 @@ sglist_append_uio(struct sglist *sg, str
if (minlen > 0) {
error = _sglist_append_buf(sg, iov[i].iov_base, minlen,
pmap, NULL);
- if (error)
+ if (error) {
+ SGLIST_RESTORE(sg, save);
return (error);
+ }
resid -= minlen;
}
}
@@ -397,6 +454,7 @@ sglist_clone(struct sglist *sg, int mfla
new = sglist_alloc(sg->sg_maxseg, mflags);
if (new == NULL)
return (NULL);
+ new->sg_nseg = sg->sg_nseg;
bcopy(sg->sg_segs, new->sg_segs, sizeof(struct sglist_seg) *
sg->sg_nseg);
return (new);
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