Re: [bug] ata subsystem related crash with latest -git

From: Jens Axboe
Date: Thu Oct 18 2007 - 04:22:44 EST

On Wed, Oct 17 2007, David Miller wrote:
> From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Date: Wed, 17 Oct 2007 18:07:19 -0700 (PDT)
>
> > sg_next() - as it stands now - never actually looks at the SG that its
> > argument points to: it explicitly *only* looks at the next one.
> >
> > That's the bug. If sg_next() looked at the actual *current* sg entry, we
> > wouldn't have any issues to begin with, and that's what I'm arguing we
> > should do in the longer run (where "longer run" is defined as "when Jens
> > does it asap").
>
> What the thing really wants is some kind of indication of state,
> without having to bloat up the scatterlist structure.
>
> I believe that we have enough of a limited set of accessors to
> sg->page that we can more aggressively encode things in the lower
> bits.
>
> I'm thinking of encoding the low two bits of sg->page as
> follows:
>
> 1) bits == 0
>
> then the SG list is linear and sg_next() is sg++
>
> 2) bits == 1
>
> the nest SG is an indirect chunk, sg_next() is
> therefore something like:
>
> next = *((struct scatterlist **)(sg + 1));
>
> 3) bits == 2
>
> this is the last entry in the scatterlist, sg_next() is NULL
>
> So for the cases of ARCH_HAS_SG_CHAIN not being set (ie. back
> compatible), we can do no bit encoding in page->flags and just do
> sg_next() == sg++, as is done now.
>
> When doing SG chaining, in each non-linear chunk we have to allocate
> one more pointer past the end of the scatterlist array (instead of a
> full extra scatterlist entry for the indirect pointer encode). Next,
> all sg->page accesses have to be guarded to clear the state bits
> out first.
>
> I don't know, maybe it would work, and would make the loop termination
> issues easier to handle properly.

I like it. Basically the only real change is using bit 2 as a
termination point, so we avoid going beyond the end of the sgtable.
Here's a starting point, it actually booted for me in the first go
(boggle). Only x86 so far, archs will need to be converted. And lots
more drivers I'm sure, I only fixed up the ones that botched my compile.

So just consider this a directional patch.

diff --git a/arch/x86/kernel/pci-gart_64.c b/arch/x86/kernel/pci-gart_64.c
index 5cdfab6..daaf636 100644
--- a/arch/x86/kernel/pci-gart_64.c
+++ b/arch/x86/kernel/pci-gart_64.c
@@ -302,7 +302,7 @@ static int dma_map_sg_nonforce(struct device *dev, struct scatterlist *sg,
#endif

for_each_sg(sg, s, nents, i) {
- unsigned long addr = page_to_phys(s->page) + s->offset;
+ unsigned long addr = page_to_phys(sg_page(s)) + s->offset;
if (nonforced_iommu(dev, addr, s->length)) {
addr = dma_map_area(dev, addr, s->length, dir);
if (addr == bad_dma_address) {
@@ -397,7 +397,7 @@ static int gart_map_sg(struct device *dev, struct scatterlist *sg, int nents,
start_sg = sgmap = sg;
ps = NULL; /* shut up gcc */
for_each_sg(sg, s, nents, i) {
- dma_addr_t addr = page_to_phys(s->page) + s->offset;
+ dma_addr_t addr = page_to_phys(sg_page(s)) + s->offset;
s->dma_address = addr;
BUG_ON(s->length == 0);

diff --git a/arch/x86/kernel/pci-nommu_64.c b/arch/x86/kernel/pci-nommu_64.c
index e85d436..d64a4a5 100644
--- a/arch/x86/kernel/pci-nommu_64.c
+++ b/arch/x86/kernel/pci-nommu_64.c
@@ -62,8 +62,8 @@ static int nommu_map_sg(struct device *hwdev, struct scatterlist *sg,
int i;

for_each_sg(sg, s, nents, i) {
- BUG_ON(!s->page);
- s->dma_address = virt_to_bus(page_address(s->page) +s->offset);
+ BUG_ON(!sg_page(s));
+ s->dma_address = virt_to_bus(page_address(sg_page(s)) +s->offset);
if (!check_addr("map_sg", hwdev, s->dma_address, s->length))
return 0;
s->dma_length = s->length;
diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index 3935469..d02783c 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -1354,10 +1354,11 @@ new_segment:
else
sg = sg_next(sg);

- memset(sg, 0, sizeof(*sg));
- sg->page = bvec->bv_page;
+ sg_set_page(sg, bvec->bv_page);
sg->length = nbytes;
sg->offset = bvec->bv_offset;
+ sg_dma_len(sg) = 0;
+ sg_dma_address(sg) = 0;
nsegs++;
}
bvprv = bvec;
diff --git a/crypto/digest.c b/crypto/digest.c
index e56de67..8871dec 100644
--- a/crypto/digest.c
+++ b/crypto/digest.c
@@ -41,7 +41,7 @@ static int update2(struct hash_desc *desc,
return 0;

for (;;) {
- struct page *pg = sg->page;
+ struct page *pg = sg_page(sg);
unsigned int offset = sg->offset;
unsigned int l = sg->length;

diff --git a/crypto/scatterwalk.c b/crypto/scatterwalk.c
index d6852c3..b9bbda0 100644
--- a/crypto/scatterwalk.c
+++ b/crypto/scatterwalk.c
@@ -54,7 +54,7 @@ static void scatterwalk_pagedone(struct scatter_walk *walk, int out,
if (out) {
struct page *page;

- page = walk->sg->page + ((walk->offset - 1) >> PAGE_SHIFT);
+ page = sg_page(walk->sg) + ((walk->offset - 1) >> PAGE_SHIFT);
flush_dcache_page(page);
}

diff --git a/crypto/scatterwalk.h b/crypto/scatterwalk.h
index 9c73e37..87ed681 100644
--- a/crypto/scatterwalk.h
+++ b/crypto/scatterwalk.h
@@ -22,13 +22,13 @@

static inline struct scatterlist *scatterwalk_sg_next(struct scatterlist *sg)
{
- return (++sg)->length ? sg : (void *)sg->page;
+ return (++sg)->length ? sg : (void *) sg_page(sg);
}

static inline unsigned long scatterwalk_samebuf(struct scatter_walk *walk_in,
struct scatter_walk *walk_out)
{
- return !(((walk_in->sg->page - walk_out->sg->page) << PAGE_SHIFT) +
+ return !(((sg_page(walk_in->sg) - sg_page(walk_out->sg)) << PAGE_SHIFT) +
(int)(walk_in->offset - walk_out->offset));
}

@@ -60,7 +60,7 @@ static inline unsigned int scatterwalk_aligned(struct scatter_walk *walk,

static inline struct page *scatterwalk_page(struct scatter_walk *walk)
{
- return walk->sg->page + (walk->offset >> PAGE_SHIFT);
+ return sg_page(walk->sg) + (walk->offset >> PAGE_SHIFT);
}

static inline void scatterwalk_unmap(void *vaddr, int out)
diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index bbaa545..b1fa70a 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -4296,7 +4296,7 @@ void ata_sg_clean(struct ata_queued_cmd *qc)
sg_last(sg, qc->orig_n_elem)->length += qc->pad_len;
if (pad_buf) {
struct scatterlist *psg = &qc->pad_sgent;
- void *addr = kmap_atomic(psg->page, KM_IRQ0);
+ void *addr = kmap_atomic(sg_page(psg), KM_IRQ0);
memcpy(addr + psg->offset, pad_buf, qc->pad_len);
kunmap_atomic(addr, KM_IRQ0);
}
@@ -4686,11 +4686,11 @@ static int ata_sg_setup(struct ata_queued_cmd *qc)
* data in this function or read data in ata_sg_clean.
*/
offset = lsg->offset + lsg->length - qc->pad_len;
- psg->page = nth_page(lsg->page, offset >> PAGE_SHIFT);
+ sg_set_page(psg, nth_page(sg_page(lsg), offset >> PAGE_SHIFT));
psg->offset = offset_in_page(offset);

if (qc->tf.flags & ATA_TFLAG_WRITE) {
- void *addr = kmap_atomic(psg->page, KM_IRQ0);
+ void *addr = kmap_atomic(sg_page(psg), KM_IRQ0);
memcpy(pad_buf, addr + psg->offset, qc->pad_len);
kunmap_atomic(addr, KM_IRQ0);
}
@@ -4836,7 +4836,7 @@ static void ata_pio_sector(struct ata_queued_cmd *qc)
if (qc->curbytes == qc->nbytes - qc->sect_size)
ap->hsm_task_state = HSM_ST_LAST;

- page = qc->cursg->page;
+ page = sg_page(qc->cursg);
offset = qc->cursg->offset + qc->cursg_ofs;

/* get the current page and offset */
@@ -4988,7 +4988,7 @@ next_sg:

sg = qc->cursg;

- page = sg->page;
+ page = sg_page(sg);
offset = sg->offset + qc->cursg_ofs;

/* get the current page and offset */
diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index 9fbb39c..5b758b9 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -1544,7 +1544,7 @@ static unsigned int ata_scsi_rbuf_get(struct scsi_cmnd *cmd, u8 **buf_out)
struct scatterlist *sg = scsi_sglist(cmd);

if (sg) {
- buf = kmap_atomic(sg->page, KM_IRQ0) + sg->offset;
+ buf = kmap_atomic(sg_page(sg), KM_IRQ0) + sg->offset;
buflen = sg->length;
} else {
buf = NULL;
diff --git a/drivers/ieee1394/dma.c b/drivers/ieee1394/dma.c
index 45d6055..25e113b 100644
--- a/drivers/ieee1394/dma.c
+++ b/drivers/ieee1394/dma.c
@@ -111,7 +111,7 @@ int dma_region_alloc(struct dma_region *dma, unsigned long n_bytes,
unsigned long va =
(unsigned long)dma->kvirt + (i << PAGE_SHIFT);

- dma->sglist[i].page = vmalloc_to_page((void *)va);
+ sg_set_page(&dma->sglist[i], vmalloc_to_page((void *)va));
dma->sglist[i].length = PAGE_SIZE;
}

diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index 72ee4c9..46cae5a 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -625,7 +625,7 @@ static int fill_from_dev_buffer(struct scsi_cmnd * scp, unsigned char * arr,
scsi_for_each_sg(scp, sg, scp->use_sg, k) {
if (active) {
kaddr = (unsigned char *)
- kmap_atomic(sg->page, KM_USER0);
+ kmap_atomic(sg_page(sg), KM_USER0);
if (NULL == kaddr)
return (DID_ERROR << 16);
kaddr_off = (unsigned char *)kaddr + sg->offset;
@@ -672,7 +672,7 @@ static int fetch_to_dev_buffer(struct scsi_cmnd * scp, unsigned char * arr,
sg = scsi_sglist(scp);
req_len = fin = 0;
for (k = 0; k < scp->use_sg; ++k, sg = sg_next(sg)) {
- kaddr = (unsigned char *)kmap_atomic(sg->page, KM_USER0);
+ kaddr = (unsigned char *)kmap_atomic(sg_page(sg), KM_USER0);
if (NULL == kaddr)
return -1;
kaddr_off = (unsigned char *)kaddr + sg->offset;
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index aac8a02..4ee32e5 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -295,7 +295,7 @@ static int scsi_req_map_sg(struct request *rq, struct scatterlist *sgl,
int i, err, nr_vecs = 0;

for_each_sg(sgl, sg, nsegs, i) {
- page = sg->page;
+ page = sg_page(sg);
off = sg->offset;
len = sg->length;
data_len += len;
@@ -781,6 +781,13 @@ struct scatterlist *scsi_alloc_sgtable(struct scsi_cmnd *cmd, gfp_t gfp_mask)
sg_chain(prev, SCSI_MAX_SG_SEGMENTS, sgl);

/*
+ * if we have nothing left, mark the last segment as
+ * end-of-list
+ */
+ if (!left)
+ sg_mark_end(sgl, this);
+
+ /*
* don't allow subsequent mempool allocs to sleep, it would
* violate the mempool principle.
*/
@@ -2353,7 +2360,7 @@ void *scsi_kmap_atomic_sg(struct scatterlist *sgl, int sg_count,
*offset = *offset - len_complete + sg->offset;

/* Assumption: contiguous pages can be accessed as "page + i" */
- page = nth_page(sg->page, (*offset >> PAGE_SHIFT));
+ page = nth_page(sg_page(sg), (*offset >> PAGE_SHIFT));
*offset &= ~PAGE_MASK;

/* Bytes in this sg-entry from *offset to the end of the page */
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 7238b2d..cc19710 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -1169,7 +1169,7 @@ sg_vma_nopage(struct vm_area_struct *vma, unsigned long addr, int *type)
len = vma->vm_end - sa;
len = (len < sg->length) ? len : sg->length;
if (offset < len) {
- page = virt_to_page(page_address(sg->page) + offset);
+ page = virt_to_page(page_address(sg_page(sg)) + offset);
get_page(page); /* increment page count */
break;
}
@@ -1717,13 +1717,13 @@ st_map_user_pages(struct scatterlist *sgl, const unsigned int max_pages,
goto out_unlock; */
}

- sgl[0].page = pages[0];
+ sg_set_page(sgl, pages[0]);
sgl[0].offset = uaddr & ~PAGE_MASK;
if (nr_pages > 1) {
sgl[0].length = PAGE_SIZE - sgl[0].offset;
count -= sgl[0].length;
for (i=1; i < nr_pages ; i++) {
- sgl[i].page = pages[i];
+ sg_set_page(&sgl[i], pages[i]);
sgl[i].length = count < PAGE_SIZE ? count : PAGE_SIZE;
count -= PAGE_SIZE;
}
@@ -1754,7 +1754,7 @@ st_unmap_user_pages(struct scatterlist *sgl, const unsigned int nr_pages,
int i;

for (i=0; i < nr_pages; i++) {
- struct page *page = sgl[i].page;
+ struct page *page = sg_page(&sgl[i]);

if (dirtied)
SetPageDirty(page);
@@ -1854,7 +1854,7 @@ sg_build_indirect(Sg_scatter_hold * schp, Sg_fd * sfp, int buff_size)
scatter_elem_sz_prev = ret_sz;
}
}
- sg->page = p;
+ sg_set_page(sg, p);
sg->length = (ret_sz > num) ? num : ret_sz;

SCSI_LOG_TIMEOUT(5, printk("sg_build_indirect: k=%d, num=%d, "
@@ -1907,14 +1907,14 @@ sg_write_xfer(Sg_request * srp)
onum = 1;

ksglen = sg->length;
- p = page_address(sg->page);
+ p = page_address(sg_page(sg));
for (j = 0, k = 0; j < onum; ++j) {
res = sg_u_iovec(hp, iovec_count, j, 1, &usglen, &up);
if (res)
return res;

for (; p; sg = sg_next(sg), ksglen = sg->length,
- p = page_address(sg->page)) {
+ p = page_address(sg_page(sg))) {
if (usglen <= 0)
break;
if (ksglen > usglen) {
@@ -1991,12 +1991,12 @@ sg_remove_scat(Sg_scatter_hold * schp)
} else {
int k;

- for (k = 0; (k < schp->k_use_sg) && sg->page;
+ for (k = 0; (k < schp->k_use_sg) && sg_page(sg);
++k, sg = sg_next(sg)) {
SCSI_LOG_TIMEOUT(5, printk(
"sg_remove_scat: k=%d, pg=0x%p, len=%d\n",
- k, sg->page, sg->length));
- sg_page_free(sg->page, sg->length);
+ k, sg_page(sg), sg->length));
+ sg_page_free(sg_page(sg), sg->length);
}
}
kfree(schp->buffer);
@@ -2038,7 +2038,7 @@ sg_read_xfer(Sg_request * srp)
} else
onum = 1;

- p = page_address(sg->page);
+ p = page_address(sg_page(sg));
ksglen = sg->length;
for (j = 0, k = 0; j < onum; ++j) {
res = sg_u_iovec(hp, iovec_count, j, 0, &usglen, &up);
@@ -2046,7 +2046,7 @@ sg_read_xfer(Sg_request * srp)
return res;

for (; p; sg = sg_next(sg), ksglen = sg->length,
- p = page_address(sg->page)) {
+ p = page_address(sg_page(sg))) {
if (usglen <= 0)
break;
if (ksglen > usglen) {
@@ -2092,15 +2092,15 @@ sg_read_oxfer(Sg_request * srp, char __user *outp, int num_read_xfer)
if ((!outp) || (num_read_xfer <= 0))
return 0;

- for (k = 0; (k < schp->k_use_sg) && sg->page; ++k, sg = sg_next(sg)) {
+ for (k = 0; (k < schp->k_use_sg) && sg_page(sg); ++k, sg = sg_next(sg)) {
num = sg->length;
if (num > num_read_xfer) {
- if (__copy_to_user(outp, page_address(sg->page),
+ if (__copy_to_user(outp, page_address(sg_page(sg)),
num_read_xfer))
return -EFAULT;
break;
} else {
- if (__copy_to_user(outp, page_address(sg->page),
+ if (__copy_to_user(outp, page_address(sg_page(sg)),
num))
return -EFAULT;
num_read_xfer -= num;
diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
index c021af3..98c455d 100644
--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -443,7 +443,7 @@ int usb_sg_init (
} else {
/* hc may use _only_ transfer_buffer */
io->urbs [i]->transfer_buffer =
- page_address (sg [i].page) + sg [i].offset;
+ page_address(sg_page(&sg[i])) + sg [i].offset;
len = sg [i].length;
}

diff --git a/drivers/usb/storage/protocol.c b/drivers/usb/storage/protocol.c
index cc8f7c5..889622b 100644
--- a/drivers/usb/storage/protocol.c
+++ b/drivers/usb/storage/protocol.c
@@ -195,7 +195,7 @@ unsigned int usb_stor_access_xfer_buf(unsigned char *buffer,
* the *offset and *index values for the next loop. */
cnt = 0;
while (cnt < buflen) {
- struct page *page = sg->page +
+ struct page *page = sg_page(sg) +
((sg->offset + *offset) >> PAGE_SHIFT);
unsigned int poff =
(sg->offset + *offset) & (PAGE_SIZE-1);
diff --git a/include/asm-x86/dma-mapping_32.h b/include/asm-x86/dma-mapping_32.h
index 6a2d26c..e0d38d8 100644
--- a/include/asm-x86/dma-mapping_32.h
+++ b/include/asm-x86/dma-mapping_32.h
@@ -45,9 +45,9 @@ dma_map_sg(struct device *dev, struct scatterlist *sglist, int nents,
WARN_ON(nents == 0 || sglist[0].length == 0);

for_each_sg(sglist, sg, nents, i) {
- BUG_ON(!sg->page);
+ BUG_ON(!sg_page(sg));

- sg->dma_address = page_to_phys(sg->page) + sg->offset;
+ sg->dma_address = page_to_phys(sg_page(sg)) + sg->offset;
}

flush_write_buffers();
diff --git a/include/asm-x86/scatterlist_32.h b/include/asm-x86/scatterlist_32.h
index bd5164a..0e7d997 100644
--- a/include/asm-x86/scatterlist_32.h
+++ b/include/asm-x86/scatterlist_32.h
@@ -4,7 +4,10 @@
#include <asm/types.h>

struct scatterlist {
- struct page *page;
+#ifdef CONFIG_DEBUG_SG
+ unsigned long sg_magic;
+#endif
+ unsigned long page_link;
unsigned int offset;
dma_addr_t dma_address;
unsigned int length;
diff --git a/include/asm-x86/scatterlist_64.h b/include/asm-x86/scatterlist_64.h
index ef3986b..1847c72 100644
--- a/include/asm-x86/scatterlist_64.h
+++ b/include/asm-x86/scatterlist_64.h
@@ -4,7 +4,10 @@
#include <asm/types.h>

struct scatterlist {
- struct page *page;
+#ifdef CONFIG_DEBUG_SG
+ unsigned long sg_magic;
+#endif
+ unsigned long page_link;
unsigned int offset;
unsigned int length;
dma_addr_t dma_address;
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 2dc7464..cbc2b57 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -5,10 +5,24 @@
#include <linux/mm.h>
#include <linux/string.h>

+#define SG_MAGIC 0x87654321
+
+static inline void sg_set_page(struct scatterlist *sg, struct page *page)
+{
+ unsigned long page_link = sg->page_link & 0x3;
+
+ sg->page_link = page_link | (unsigned long) page;
+}
+
+#define sg_page(sg) ((struct page *) ((sg)->page_link & ~0x3))
+
static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
unsigned int buflen)
{
- sg->page = virt_to_page(buf);
+#ifdef CONFIG_DEBUG_SG
+ sg->sg_magic = SG_MAGIC;
+#endif
+ sg_set_page(sg, virt_to_page(buf));
sg->offset = offset_in_page(buf);
sg->length = buflen;
}
@@ -25,9 +39,9 @@ static inline void sg_init_one(struct scatterlist *sg, const void *buf,
* a valid sg entry, or whether it points to the start of a new scatterlist.
* Those low bits are there for everyone! (thanks mason :-)
*/
-#define sg_is_chain(sg) ((unsigned long) (sg)->page & 0x01)
-#define sg_chain_ptr(sg) \
- ((struct scatterlist *) ((unsigned long) (sg)->page & ~0x01))
+#define sg_is_chain(sg) ((sg)->page_link & 0x01)
+#define sg_is_last(sg) ((sg)->page_link & 0x02)
+#define sg_chain_ptr(sg) ((struct scatterlist *) ((sg)->page_link & ~0x01))

/**
* sg_next - return the next scatterlist entry in a list
@@ -43,10 +57,15 @@ static inline void sg_init_one(struct scatterlist *sg, const void *buf,
*/
static inline struct scatterlist *sg_next(struct scatterlist *sg)
{
- sg++;
-
- if (unlikely(sg_is_chain(sg)))
+#ifdef CONFIG_DEBUG_SG
+ BUG_ON(sg->sg_magic != SG_MAGIC);
+#endif
+ if (sg_is_last(sg))
+ sg = NULL;
+ else if (sg_is_chain(sg))
sg = sg_chain_ptr(sg);
+ else
+ sg++;

return sg;
}
@@ -83,6 +102,9 @@ static inline struct scatterlist *sg_last(struct scatterlist *sgl,
ret = sg;

#endif
+#ifdef CONFIG_DEBUG_SG
+ BUG_ON(sgl[0].sg_magic != SG_MAGIC);
+#endif
return ret;
}

@@ -101,7 +123,41 @@ static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
#ifndef ARCH_HAS_SG_CHAIN
BUG();
#endif
- prv[prv_nents - 1].page = (struct page *) ((unsigned long) sgl | 0x01);
+ prv[prv_nents - 1].page_link = (unsigned long) sgl | 0x01;
+}
+
+/**
+ * sg_mark_end - Mark the end of the scatterlist
+ * @sgl: Scatterlist
+ * @nents: Number of entries in sgl
+ *
+ * Marks the last entry as the termination point for sg_next()
+ *
+ */
+static inline void sg_mark_end(struct scatterlist *sgl, unsigned int nents)
+{
+ sgl[nents - 1].page_link = 0x02;
+}
+
+/**
+ * sg_init_table - Initialize an sg table
+ * @sgl: Scatterlist
+ * @nents: Number of entries in sgl
+ *
+ * Marks the last entry as the termination point for sg_next()
+ *
+ */
+static inline void sg_init_table(struct scatterlist *sgl, unsigned int nents)
+{
+ memset(sgl, 0, sizeof(*sgl) * nents);
+ sg_mark_end(sgl, nents);
+#ifdef CONFIG_DEBUG_SG
+ {
+ int i;
+ for (i = 0; i < nents; i++)
+ sgl[i].sg_magic = SG_MAGIC;
+ }
+#endif
}

#endif /* _LINUX_SCATTERLIST_H */
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 7d16e64..c17aace 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -389,6 +389,17 @@ config DEBUG_LIST

If unsure, say N.

+config DEBUG_SG
+ bool "Debug SG table operations"
+ depends on DEBUG_KERNEL
+ help
+ Enable this to turn on checks on scatter-gather tables. This can
+ help find problems with drivers that do not properly initialize
+ their sg tables. Runtime overhead is very small, but it does
+ increase an sg entry by sizeof(unsigned long).
+
+ If unsure, say N.
+
config FRAME_POINTER
bool "Compile the kernel with frame pointers"
depends on DEBUG_KERNEL && (X86 || CRIS || M68K || M68KNOMMU || FRV || UML || S390 || AVR32 || SUPERH || BFIN)
diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index 752fd95..e58909e 100644
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -35,7 +35,7 @@
#define OFFSET(val,align) ((unsigned long) \
( (val) & ( (align) - 1)))

-#define SG_ENT_VIRT_ADDRESS(sg) (page_address((sg)->page) + (sg)->offset)
+#define SG_ENT_VIRT_ADDRESS(sg) (page_address(sg_page((sg)) + (sg)->offset))
#define SG_ENT_PHYS_ADDRESS(sg) virt_to_bus(SG_ENT_VIRT_ADDRESS(sg))

/*
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 70d9b5d..4e2c84f 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2045,7 +2045,7 @@ skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
if (copy > 0) {
if (copy > len)
copy = len;
- sg[elt].page = virt_to_page(skb->data + offset);
+ sg_set_page(&sg[elt], virt_to_page(skb->data + offset));
sg[elt].offset = (unsigned long)(skb->data + offset) % PAGE_SIZE;
sg[elt].length = copy;
elt++;
@@ -2065,7 +2065,7 @@ skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)

if (copy > len)
copy = len;
- sg[elt].page = frag->page;
+ sg_set_page(&sg[elt], frag->page);
sg[elt].offset = frag->page_offset+offset-start;
sg[elt].length = copy;
elt++;
diff --git a/net/ieee80211/ieee80211_crypt_wep.c b/net/ieee80211/ieee80211_crypt_wep.c
index 8d18245..1a77877 100644
--- a/net/ieee80211/ieee80211_crypt_wep.c
+++ b/net/ieee80211/ieee80211_crypt_wep.c
@@ -170,7 +170,8 @@ static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
icv[3] = crc >> 24;

crypto_blkcipher_setkey(wep->tx_tfm, key, klen);
- sg.page = virt_to_page(pos);
+ sg_init_table(&sg, 1);
+ sg_set_page(&sg, virt_to_page(pos));
sg.offset = offset_in_page(pos);
sg.length = len + 4;
return crypto_blkcipher_encrypt(&desc, &sg, &sg, len + 4);
@@ -212,7 +213,8 @@ static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
plen = skb->len - hdr_len - 8;

crypto_blkcipher_setkey(wep->rx_tfm, key, klen);
- sg.page = virt_to_page(pos);
+ sg_init_table(&sg, 1);
+ sg_set_page(&sg, virt_to_page(pos));
sg.offset = offset_in_page(pos);
sg.length = plen + 4;
if (crypto_blkcipher_decrypt(&desc, &sg, &sg, plen + 4))
diff --git a/net/mac80211/wep.c b/net/mac80211/wep.c
index 6675261..9857961 100644
--- a/net/mac80211/wep.c
+++ b/net/mac80211/wep.c
@@ -138,7 +138,8 @@ void ieee80211_wep_encrypt_data(struct crypto_blkcipher *tfm, u8 *rc4key,
*icv = cpu_to_le32(~crc32_le(~0, data, data_len));

crypto_blkcipher_setkey(tfm, rc4key, klen);
- sg.page = virt_to_page(data);
+ sg_init_table(&sg, 1);
+ sg_set_page(&sg, virt_to_page(data));
sg.offset = offset_in_page(data);
sg.length = data_len + WEP_ICV_LEN;
crypto_blkcipher_encrypt(&desc, &sg, &sg, sg.length);
@@ -204,7 +205,8 @@ int ieee80211_wep_decrypt_data(struct crypto_blkcipher *tfm, u8 *rc4key,
__le32 crc;

crypto_blkcipher_setkey(tfm, rc4key, klen);
- sg.page = virt_to_page(data);
+ sg_init_table(&sg, 1);
+ sg_set_page(&sg, virt_to_page(data));
sg.offset = offset_in_page(data);
sg.length = data_len + WEP_ICV_LEN;
crypto_blkcipher_decrypt(&desc, &sg, &sg, sg.length);
diff --git a/net/sunrpc/auth_gss/gss_krb5_crypto.c b/net/sunrpc/auth_gss/gss_krb5_crypto.c
index bfb6a29..32be431 100644
--- a/net/sunrpc/auth_gss/gss_krb5_crypto.c
+++ b/net/sunrpc/auth_gss/gss_krb5_crypto.c
@@ -197,9 +197,9 @@ encryptor(struct scatterlist *sg, void *data)
int i = (page_pos + outbuf->page_base) >> PAGE_CACHE_SHIFT;
in_page = desc->pages[i];
} else {
- in_page = sg->page;
+ in_page = sg_page(sg);
}
- desc->infrags[desc->fragno].page = in_page;
+ sg_set_page(&desc->infrags[desc->fragno], in_page);
desc->fragno++;
desc->fraglen += sg->length;
desc->pos += sg->length;
@@ -215,11 +215,11 @@ encryptor(struct scatterlist *sg, void *data)
if (ret)
return ret;
if (fraglen) {
- desc->outfrags[0].page = sg->page;
+ sg_set_page(&desc->outfrags[0], sg_page(sg));
desc->outfrags[0].offset = sg->offset + sg->length - fraglen;
desc->outfrags[0].length = fraglen;
desc->infrags[0] = desc->outfrags[0];
- desc->infrags[0].page = in_page;
+ sg_set_page(&desc->infrags[0], in_page);
desc->fragno = 1;
desc->fraglen = fraglen;
} else {
@@ -287,7 +287,7 @@ decryptor(struct scatterlist *sg, void *data)
if (ret)
return ret;
if (fraglen) {
- desc->frags[0].page = sg->page;
+ sg_set_page(&desc->frags[0], sg_page(sg));
desc->frags[0].offset = sg->offset + sg->length - fraglen;
desc->frags[0].length = fraglen;
desc->fragno = 1;
diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index 6a59180..3d1f7cd 100644
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -1059,7 +1059,7 @@ xdr_process_buf(struct xdr_buf *buf, unsigned int offset, unsigned int len,
do {
if (thislen > page_len)
thislen = page_len;
- sg->page = buf->pages[i];
+ sg_set_page(sg, buf->pages[i]);
sg->offset = page_offset;
sg->length = thislen;
ret = actor(sg, data);
diff --git a/net/xfrm/xfrm_algo.c b/net/xfrm/xfrm_algo.c
index 5ced62c..fb2220a 100644
--- a/net/xfrm/xfrm_algo.c
+++ b/net/xfrm/xfrm_algo.c
@@ -552,7 +552,7 @@ int skb_icv_walk(const struct sk_buff *skb, struct hash_desc *desc,
if (copy > len)
copy = len;

- sg.page = virt_to_page(skb->data + offset);
+ sg_set_page(&sg, virt_to_page(skb->data + offset));
sg.offset = (unsigned long)(skb->data + offset) % PAGE_SIZE;
sg.length = copy;

@@ -577,7 +577,7 @@ int skb_icv_walk(const struct sk_buff *skb, struct hash_desc *desc,
if (copy > len)
copy = len;

- sg.page = frag->page;
+ sg_set_page(&sg, frag->page);
sg.offset = frag->page_offset + offset-start;
sg.length = copy;


--
Jens Axboe

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