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)
This commit is contained in:
John Baldwin
parent
eb4d96a268
commit
eb5a1e8f38
@ -191,6 +191,8 @@ Specifically, the
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family of routines can be used to append the physical address ranges described
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by an object to the end of a scatter/gather list.
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All of these routines return 0 on success or an error on failure.
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If a request to append an address range to a scatter/gather list fails,
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the scatter/gather list will remain unchanged.
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.Pp
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The
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.Nm sglist_append
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@ -445,6 +447,7 @@ There are not enough available segments in the scatter/gather list
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to append the physical address ranges from
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.Fa second .
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.El
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.Pp
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The
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.Nm sglist_slice
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function returns the following errors on failure:
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@ -470,6 +473,7 @@ list in
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.Fa *slice
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to describe the requested physical address ranges.
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.El
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.Pp
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The
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.Nm sglist_split
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function returns the following errors on failure:
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@ -47,6 +47,32 @@ __FBSDID("$FreeBSD$");
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static MALLOC_DEFINE(M_SGLIST, "sglist", "scatter/gather lists");
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/*
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* Convenience macros to save the state of an sglist so it can be restored
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* if an append attempt fails. Since sglist's only grow we only need to
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* save the current count of segments and the length of the ending segment.
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* Earlier segments will not be changed by an append, and the only change
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* that can occur to the ending segment is that it can be extended.
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*/
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struct sgsave {
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u_short sg_nseg;
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size_t ss_len;
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};
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#define SGLIST_SAVE(sg, sgsave) do { \
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(sgsave).sg_nseg = (sg)->sg_nseg; \
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if ((sgsave).sg_nseg > 0) \
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(sgsave).ss_len = (sg)->sg_segs[(sgsave).sg_nseg - 1].ss_len; \
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else \
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(sgsave).ss_len = 0; \
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} while (0)
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#define SGLIST_RESTORE(sg, sgsave) do { \
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(sg)->sg_nseg = (sgsave).sg_nseg; \
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if ((sgsave).sg_nseg > 0) \
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(sg)->sg_segs[(sgsave).sg_nseg - 1].ss_len = (sgsave).ss_len; \
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} while (0)
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/*
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* Append a single (paddr, len) to a sglist. sg is the list and ss is
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* the current segment in the list. If we run out of segments then
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@ -62,10 +88,8 @@ _sglist_append_range(struct sglist *sg, struct sglist_seg **ssp,
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if (ss->ss_paddr + ss->ss_len == paddr)
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ss->ss_len += len;
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else {
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if (sg->sg_nseg == sg->sg_maxseg) {
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sg->sg_nseg = 0;
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if (sg->sg_nseg == sg->sg_maxseg)
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return (EFBIG);
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}
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ss++;
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ss->ss_paddr = paddr;
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ss->ss_len = len;
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@ -107,26 +131,33 @@ _sglist_append_buf(struct sglist *sg, void *buf, size_t len, pmap_t pmap,
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ss->ss_paddr = paddr;
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ss->ss_len = seglen;
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sg->sg_nseg = 1;
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error = 0;
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} else {
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ss = &sg->sg_segs[sg->sg_nseg - 1];
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error = _sglist_append_range(sg, &ss, paddr, seglen);
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if (error)
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return (error);
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}
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vaddr += seglen;
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len -= seglen;
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if (donep)
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*donep += seglen;
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while (error == 0 && len > seglen) {
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vaddr += seglen;
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len -= seglen;
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if (donep)
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*donep += seglen;
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while (len > 0) {
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seglen = MIN(len, PAGE_SIZE);
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if (pmap != NULL)
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paddr = pmap_extract(pmap, vaddr);
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else
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paddr = pmap_kextract(vaddr);
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error = _sglist_append_range(sg, &ss, paddr, seglen);
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if (error)
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return (error);
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vaddr += seglen;
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len -= seglen;
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if (donep)
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*donep += seglen;
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}
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return (error);
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return (0);
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}
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/*
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@ -195,10 +226,16 @@ sglist_free(struct sglist *sg)
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int
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sglist_append(struct sglist *sg, void *buf, size_t len)
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{
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struct sgsave save;
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int error;
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if (sg->sg_maxseg == 0)
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return (EINVAL);
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return (_sglist_append_buf(sg, buf, len, NULL, NULL));
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SGLIST_SAVE(sg, save);
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error = _sglist_append_buf(sg, buf, len, NULL, NULL);
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if (error)
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SGLIST_RESTORE(sg, save);
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return (error);
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}
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/*
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@ -209,6 +246,8 @@ int
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sglist_append_phys(struct sglist *sg, vm_paddr_t paddr, size_t len)
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{
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struct sglist_seg *ss;
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struct sgsave save;
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int error;
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if (sg->sg_maxseg == 0)
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return (EINVAL);
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@ -222,7 +261,11 @@ sglist_append_phys(struct sglist *sg, vm_paddr_t paddr, size_t len)
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return (0);
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}
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ss = &sg->sg_segs[sg->sg_nseg - 1];
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return (_sglist_append_range(sg, &ss, paddr, len));
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SGLIST_SAVE(sg, save);
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error = _sglist_append_range(sg, &ss, paddr, len);
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if (error)
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SGLIST_RESTORE(sg, save);
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return (error);
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}
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/*
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@ -233,6 +276,7 @@ sglist_append_phys(struct sglist *sg, vm_paddr_t paddr, size_t len)
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int
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sglist_append_mbuf(struct sglist *sg, struct mbuf *m0)
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{
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struct sgsave save;
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struct mbuf *m;
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int error;
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@ -240,11 +284,14 @@ sglist_append_mbuf(struct sglist *sg, struct mbuf *m0)
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return (EINVAL);
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error = 0;
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SGLIST_SAVE(sg, save);
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for (m = m0; m != NULL; m = m->m_next) {
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if (m->m_len > 0) {
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error = sglist_append(sg, m->m_data, m->m_len);
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if (error)
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if (error) {
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SGLIST_RESTORE(sg, save);
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return (error);
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}
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}
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}
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return (0);
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@ -258,11 +305,17 @@ sglist_append_mbuf(struct sglist *sg, struct mbuf *m0)
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int
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sglist_append_user(struct sglist *sg, void *buf, size_t len, struct thread *td)
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{
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struct sgsave save;
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int error;
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if (sg->sg_maxseg == 0)
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return (EINVAL);
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return (_sglist_append_buf(sg, buf, len,
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vmspace_pmap(td->td_proc->p_vmspace), NULL));
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SGLIST_SAVE(sg, save);
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error = _sglist_append_buf(sg, buf, len,
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vmspace_pmap(td->td_proc->p_vmspace), NULL);
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if (error)
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SGLIST_RESTORE(sg, save);
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return (error);
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}
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/*
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@ -274,6 +327,7 @@ int
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sglist_append_uio(struct sglist *sg, struct uio *uio)
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{
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struct iovec *iov;
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struct sgsave save;
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size_t resid, minlen;
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pmap_t pmap;
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int error, i;
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@ -292,6 +346,7 @@ sglist_append_uio(struct sglist *sg, struct uio *uio)
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pmap = NULL;
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error = 0;
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SGLIST_SAVE(sg, save);
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for (i = 0; i < uio->uio_iovcnt && resid != 0; i++) {
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/*
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* Now at the first iovec to load. Load each iovec
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@ -301,8 +356,10 @@ sglist_append_uio(struct sglist *sg, struct uio *uio)
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if (minlen > 0) {
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error = _sglist_append_buf(sg, iov[i].iov_base, minlen,
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pmap, NULL);
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if (error)
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if (error) {
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SGLIST_RESTORE(sg, save);
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return (error);
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}
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resid -= minlen;
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}
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}
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@ -397,6 +454,7 @@ sglist_clone(struct sglist *sg, int mflags)
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new = sglist_alloc(sg->sg_maxseg, mflags);
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if (new == NULL)
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return (NULL);
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new->sg_nseg = sg->sg_nseg;
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bcopy(sg->sg_segs, new->sg_segs, sizeof(struct sglist_seg) *
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sg->sg_nseg);
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return (new);
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