Re: [PATCH v4] mmap_vmcore: skip non-ram pages reported by hypervisors
Sorry for delayed responce...
(2014/07/11 17:49), Vitaly Kuznetsov wrote:
> We have a special check in read_vmcore() handler to check if the page was
> reported as ram or not by the hypervisor (pfn_is_ram()). However, when
> vmcore is read with mmap() no such check is performed. That can lead to
> unpredictable results, e.g. when running Xen PVHVM guest memcpy() after
> mmap() on /proc/vmcore will hang processing HVMMEM_mmio_dm pages creating
> enormous load in both DomU and Dom0.
>
> Fix the issue by mapping each non-ram page to the zero page. Keep direct
> path with remap_oldmem_pfn_range() to avoid looping through all pages on
> bare metal.
>
> The issue can also be solved by overriding remap_oldmem_pfn_range() in
> xen-specific code, as remap_oldmem_pfn_range() was been designed for.
> That, however, would involve non-obvious xen code path for all x86 builds
> with CONFIG_XEN_PVHVM=y and would prevent all other hypervisor-specific
> code on x86 arch from doing the same override.
>
> Changes from v3:
> - multi line comment style changes
> - minor code style changes
>
> Changes from v2:
> - make remap_oldmem_pfn_checked() interface exactly match
>remap_oldmem_pfn_range()
> - unmap mapped part inside remap_oldmem_pfn_checked() in case of failure so
>we don't need to take care of it in mmap_vmcore()
> - create vmcore_remap_oldmem_pfn() wrapper
>
> Changes from v1:
> - comment style changes
> - change remap_oldmem_pfn_checked() interface to closer match the
>remap_oldmem_pfn() interface
> - preserve formal parameters within the loop, make the loop conditions
>easier to understand
> - use my_zero_pfn() for the zero page
> - return remapped length instead of new offset
>
> Signed-off-by: Vitaly Kuznetsov
> Reviewed-by: Andrew Jones
> ---
> fs/proc/vmcore.c | 83
> ++--
> 1 file changed, 80 insertions(+), 3 deletions(-)
>
> diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
> index 382aa89..405a409 100644
> --- a/fs/proc/vmcore.c
> +++ b/fs/proc/vmcore.c
> @@ -328,6 +328,83 @@ static inline char *alloc_elfnotes_buf(size_t notes_sz)
>* virtually contiguous user-space in ELF layout.
>*/
> #ifdef CONFIG_MMU
> +/*
> + * remap_oldmem_pfn_checked - do remap_oldmem_pfn_range replacing all pages
> + * reported as not being ram with the zero page.
> + *
> + * @vma: vm_area_struct describing requested mapping
> + * @from: start remapping from
> + * @pfn: page frame number to start remapping to
> + * @size: remapping size
> + * @prot: protection bits
> + *
> + * Returns zero on success, -EAGAIN on failure.
> + */
> +int remap_oldmem_pfn_checked(struct vm_area_struct *vma, unsigned long from,
> + unsigned long pfn, unsigned long size,
> + pgprot_t prot)
> +{
> + size_t map_size;
unsigned long is better? At least all the occurences of this variable in
this function is used as unsigned long.
> + unsigned long pos_start, pos_end, pos;
> + unsigned long zeropage_pfn = my_zero_pfn(0);
> + u64 len = 0;
> +
> + pos_start = pfn;
> + pos_end = pfn + (size >> PAGE_SHIFT);
> +
> + for (pos = pos_start; pos < pos_end; ++pos) {
> + if (!pfn_is_ram(pos)) {
> + /*
> + * We hit a page which is not ram. Remap the continuous
> + * region between pos_start and pos-1 and replace
> + * the non-ram page at pos with the zero page.
> + */
> + if (pos > pos_start) {
> + /* Remap continuous region */
> + map_size = (pos - pos_start) << PAGE_SHIFT;
> + if (remap_oldmem_pfn_range(vma, from + len,
> +pos_start, map_size,
> +prot))
> + goto fail;
> + len += map_size;
> + }
> + /* Remap the zero page */
> + if (remap_oldmem_pfn_range(vma, from + len,
> +zeropage_pfn,
> +PAGE_SIZE, prot))
> + goto fail;
> + len += PAGE_SIZE;
> + pos_start = pos + 1;
> + }
> + }
> + if (pos > pos_start) {
> + /* Remap the rest */
> + map_size = (pos - pos_start) << PAGE_SHIFT;
> + if (remap_oldmem_pfn_range(vma, from + len, pos_start,
> +map_size, vma->vm_page_prot))
Is prot correct here?
> + goto fail;
> + len += map_size;
> + }
> + return 0;
> +fail:
> + do_munmap(vma->vm_mm, from, len);
> + return
Re: [PATCH v4] mmap_vmcore: skip non-ram pages reported by hypervisors
Sorry for delayed responce...
(2014/07/11 17:49), Vitaly Kuznetsov wrote:
We have a special check in read_vmcore() handler to check if the page was
reported as ram or not by the hypervisor (pfn_is_ram()). However, when
vmcore is read with mmap() no such check is performed. That can lead to
unpredictable results, e.g. when running Xen PVHVM guest memcpy() after
mmap() on /proc/vmcore will hang processing HVMMEM_mmio_dm pages creating
enormous load in both DomU and Dom0.
Fix the issue by mapping each non-ram page to the zero page. Keep direct
path with remap_oldmem_pfn_range() to avoid looping through all pages on
bare metal.
The issue can also be solved by overriding remap_oldmem_pfn_range() in
xen-specific code, as remap_oldmem_pfn_range() was been designed for.
That, however, would involve non-obvious xen code path for all x86 builds
with CONFIG_XEN_PVHVM=y and would prevent all other hypervisor-specific
code on x86 arch from doing the same override.
Changes from v3:
- multi line comment style changes
- minor code style changes
Changes from v2:
- make remap_oldmem_pfn_checked() interface exactly match
remap_oldmem_pfn_range()
- unmap mapped part inside remap_oldmem_pfn_checked() in case of failure so
we don't need to take care of it in mmap_vmcore()
- create vmcore_remap_oldmem_pfn() wrapper
Changes from v1:
- comment style changes
- change remap_oldmem_pfn_checked() interface to closer match the
remap_oldmem_pfn() interface
- preserve formal parameters within the loop, make the loop conditions
easier to understand
- use my_zero_pfn() for the zero page
- return remapped length instead of new offset
Signed-off-by: Vitaly Kuznetsov vkuzn...@redhat.com
Reviewed-by: Andrew Jones drjo...@redhat.com
---
fs/proc/vmcore.c | 83
++--
1 file changed, 80 insertions(+), 3 deletions(-)
diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index 382aa89..405a409 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -328,6 +328,83 @@ static inline char *alloc_elfnotes_buf(size_t notes_sz)
* virtually contiguous user-space in ELF layout.
*/
#ifdef CONFIG_MMU
+/*
+ * remap_oldmem_pfn_checked - do remap_oldmem_pfn_range replacing all pages
+ * reported as not being ram with the zero page.
+ *
+ * @vma: vm_area_struct describing requested mapping
+ * @from: start remapping from
+ * @pfn: page frame number to start remapping to
+ * @size: remapping size
+ * @prot: protection bits
+ *
+ * Returns zero on success, -EAGAIN on failure.
+ */
+int remap_oldmem_pfn_checked(struct vm_area_struct *vma, unsigned long from,
+ unsigned long pfn, unsigned long size,
+ pgprot_t prot)
+{
+ size_t map_size;
unsigned long is better? At least all the occurences of this variable in
this function is used as unsigned long.
+ unsigned long pos_start, pos_end, pos;
+ unsigned long zeropage_pfn = my_zero_pfn(0);
+ u64 len = 0;
+
+ pos_start = pfn;
+ pos_end = pfn + (size PAGE_SHIFT);
+
+ for (pos = pos_start; pos pos_end; ++pos) {
+ if (!pfn_is_ram(pos)) {
+ /*
+ * We hit a page which is not ram. Remap the continuous
+ * region between pos_start and pos-1 and replace
+ * the non-ram page at pos with the zero page.
+ */
+ if (pos pos_start) {
+ /* Remap continuous region */
+ map_size = (pos - pos_start) PAGE_SHIFT;
+ if (remap_oldmem_pfn_range(vma, from + len,
+pos_start, map_size,
+prot))
+ goto fail;
+ len += map_size;
+ }
+ /* Remap the zero page */
+ if (remap_oldmem_pfn_range(vma, from + len,
+zeropage_pfn,
+PAGE_SIZE, prot))
+ goto fail;
+ len += PAGE_SIZE;
+ pos_start = pos + 1;
+ }
+ }
+ if (pos pos_start) {
+ /* Remap the rest */
+ map_size = (pos - pos_start) PAGE_SHIFT;
+ if (remap_oldmem_pfn_range(vma, from + len, pos_start,
+map_size, vma-vm_page_prot))
Is prot correct here?
+ goto fail;
+ len += map_size;
+ }
+ return 0;
+fail:
+ do_munmap(vma-vm_mm, from, len);
+ return -EAGAIN;
+}
+
+int vmcore_remap_oldmem_pfn(struct vm_area_struct *vma,
+
Re: [PATCH v4] mmap_vmcore: skip non-ram pages reported by hypervisors
On Fri, Jul 11, 2014 at 10:49:12AM +0200, Vitaly Kuznetsov wrote:
> We have a special check in read_vmcore() handler to check if the page was
> reported as ram or not by the hypervisor (pfn_is_ram()). However, when
> vmcore is read with mmap() no such check is performed. That can lead to
> unpredictable results, e.g. when running Xen PVHVM guest memcpy() after
> mmap() on /proc/vmcore will hang processing HVMMEM_mmio_dm pages creating
> enormous load in both DomU and Dom0.
>
> Fix the issue by mapping each non-ram page to the zero page. Keep direct
> path with remap_oldmem_pfn_range() to avoid looping through all pages on
> bare metal.
>
> The issue can also be solved by overriding remap_oldmem_pfn_range() in
> xen-specific code, as remap_oldmem_pfn_range() was been designed for.
> That, however, would involve non-obvious xen code path for all x86 builds
> with CONFIG_XEN_PVHVM=y and would prevent all other hypervisor-specific
> code on x86 arch from doing the same override.
>
> Changes from v3:
> - multi line comment style changes
> - minor code style changes
>
> Changes from v2:
> - make remap_oldmem_pfn_checked() interface exactly match
> remap_oldmem_pfn_range()
> - unmap mapped part inside remap_oldmem_pfn_checked() in case of failure so
> we don't need to take care of it in mmap_vmcore()
> - create vmcore_remap_oldmem_pfn() wrapper
>
> Changes from v1:
> - comment style changes
> - change remap_oldmem_pfn_checked() interface to closer match the
> remap_oldmem_pfn() interface
> - preserve formal parameters within the loop, make the loop conditions
> easier to understand
> - use my_zero_pfn() for the zero page
> - return remapped length instead of new offset
>
> Signed-off-by: Vitaly Kuznetsov
> Reviewed-by: Andrew Jones
This one looks good to me. Thanks.
Acked-by: Vivek Goyal
Vivek
> ---
> fs/proc/vmcore.c | 83
> ++--
> 1 file changed, 80 insertions(+), 3 deletions(-)
>
> diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
> index 382aa89..405a409 100644
> --- a/fs/proc/vmcore.c
> +++ b/fs/proc/vmcore.c
> @@ -328,6 +328,83 @@ static inline char *alloc_elfnotes_buf(size_t notes_sz)
> * virtually contiguous user-space in ELF layout.
> */
> #ifdef CONFIG_MMU
> +/*
> + * remap_oldmem_pfn_checked - do remap_oldmem_pfn_range replacing all pages
> + * reported as not being ram with the zero page.
> + *
> + * @vma: vm_area_struct describing requested mapping
> + * @from: start remapping from
> + * @pfn: page frame number to start remapping to
> + * @size: remapping size
> + * @prot: protection bits
> + *
> + * Returns zero on success, -EAGAIN on failure.
> + */
> +int remap_oldmem_pfn_checked(struct vm_area_struct *vma, unsigned long from,
> + unsigned long pfn, unsigned long size,
> + pgprot_t prot)
> +{
> + size_t map_size;
> + unsigned long pos_start, pos_end, pos;
> + unsigned long zeropage_pfn = my_zero_pfn(0);
> + u64 len = 0;
> +
> + pos_start = pfn;
> + pos_end = pfn + (size >> PAGE_SHIFT);
> +
> + for (pos = pos_start; pos < pos_end; ++pos) {
> + if (!pfn_is_ram(pos)) {
> + /*
> + * We hit a page which is not ram. Remap the continuous
> + * region between pos_start and pos-1 and replace
> + * the non-ram page at pos with the zero page.
> + */
> + if (pos > pos_start) {
> + /* Remap continuous region */
> + map_size = (pos - pos_start) << PAGE_SHIFT;
> + if (remap_oldmem_pfn_range(vma, from + len,
> +pos_start, map_size,
> +prot))
> + goto fail;
> + len += map_size;
> + }
> + /* Remap the zero page */
> + if (remap_oldmem_pfn_range(vma, from + len,
> +zeropage_pfn,
> +PAGE_SIZE, prot))
> + goto fail;
> + len += PAGE_SIZE;
> + pos_start = pos + 1;
> + }
> + }
> + if (pos > pos_start) {
> + /* Remap the rest */
> + map_size = (pos - pos_start) << PAGE_SHIFT;
> + if (remap_oldmem_pfn_range(vma, from + len, pos_start,
> +map_size, vma->vm_page_prot))
> + goto fail;
> + len += map_size;
> + }
> + return 0;
> +fail:
> + do_munmap(vma->vm_mm, from, len);
> + return -EAGAIN;
> +}
> +
> +int vmcore_remap_oldmem_pfn(struct vm_area_struct *vma,
> + unsigned long from, unsigned long
[PATCH v4] mmap_vmcore: skip non-ram pages reported by hypervisors
We have a special check in read_vmcore() handler to check if the page was
reported as ram or not by the hypervisor (pfn_is_ram()). However, when
vmcore is read with mmap() no such check is performed. That can lead to
unpredictable results, e.g. when running Xen PVHVM guest memcpy() after
mmap() on /proc/vmcore will hang processing HVMMEM_mmio_dm pages creating
enormous load in both DomU and Dom0.
Fix the issue by mapping each non-ram page to the zero page. Keep direct
path with remap_oldmem_pfn_range() to avoid looping through all pages on
bare metal.
The issue can also be solved by overriding remap_oldmem_pfn_range() in
xen-specific code, as remap_oldmem_pfn_range() was been designed for.
That, however, would involve non-obvious xen code path for all x86 builds
with CONFIG_XEN_PVHVM=y and would prevent all other hypervisor-specific
code on x86 arch from doing the same override.
Changes from v3:
- multi line comment style changes
- minor code style changes
Changes from v2:
- make remap_oldmem_pfn_checked() interface exactly match
remap_oldmem_pfn_range()
- unmap mapped part inside remap_oldmem_pfn_checked() in case of failure so
we don't need to take care of it in mmap_vmcore()
- create vmcore_remap_oldmem_pfn() wrapper
Changes from v1:
- comment style changes
- change remap_oldmem_pfn_checked() interface to closer match the
remap_oldmem_pfn() interface
- preserve formal parameters within the loop, make the loop conditions
easier to understand
- use my_zero_pfn() for the zero page
- return remapped length instead of new offset
Signed-off-by: Vitaly Kuznetsov
Reviewed-by: Andrew Jones
---
fs/proc/vmcore.c | 83 ++--
1 file changed, 80 insertions(+), 3 deletions(-)
diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index 382aa89..405a409 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -328,6 +328,83 @@ static inline char *alloc_elfnotes_buf(size_t notes_sz)
* virtually contiguous user-space in ELF layout.
*/
#ifdef CONFIG_MMU
+/*
+ * remap_oldmem_pfn_checked - do remap_oldmem_pfn_range replacing all pages
+ * reported as not being ram with the zero page.
+ *
+ * @vma: vm_area_struct describing requested mapping
+ * @from: start remapping from
+ * @pfn: page frame number to start remapping to
+ * @size: remapping size
+ * @prot: protection bits
+ *
+ * Returns zero on success, -EAGAIN on failure.
+ */
+int remap_oldmem_pfn_checked(struct vm_area_struct *vma, unsigned long from,
+unsigned long pfn, unsigned long size,
+pgprot_t prot)
+{
+ size_t map_size;
+ unsigned long pos_start, pos_end, pos;
+ unsigned long zeropage_pfn = my_zero_pfn(0);
+ u64 len = 0;
+
+ pos_start = pfn;
+ pos_end = pfn + (size >> PAGE_SHIFT);
+
+ for (pos = pos_start; pos < pos_end; ++pos) {
+ if (!pfn_is_ram(pos)) {
+ /*
+* We hit a page which is not ram. Remap the continuous
+* region between pos_start and pos-1 and replace
+* the non-ram page at pos with the zero page.
+*/
+ if (pos > pos_start) {
+ /* Remap continuous region */
+ map_size = (pos - pos_start) << PAGE_SHIFT;
+ if (remap_oldmem_pfn_range(vma, from + len,
+ pos_start, map_size,
+ prot))
+ goto fail;
+ len += map_size;
+ }
+ /* Remap the zero page */
+ if (remap_oldmem_pfn_range(vma, from + len,
+ zeropage_pfn,
+ PAGE_SIZE, prot))
+ goto fail;
+ len += PAGE_SIZE;
+ pos_start = pos + 1;
+ }
+ }
+ if (pos > pos_start) {
+ /* Remap the rest */
+ map_size = (pos - pos_start) << PAGE_SHIFT;
+ if (remap_oldmem_pfn_range(vma, from + len, pos_start,
+ map_size, vma->vm_page_prot))
+ goto fail;
+ len += map_size;
+ }
+ return 0;
+fail:
+ do_munmap(vma->vm_mm, from, len);
+ return -EAGAIN;
+}
+
+int vmcore_remap_oldmem_pfn(struct vm_area_struct *vma,
+ unsigned long from, unsigned long pfn,
+ unsigned long size, pgprot_t prot)
+{
+ /*
+* Check if oldmem_pfn_is_ram was registered to avoid
+* looping over all pages without a reason.
+*/
+ if (oldmem_pfn_is_ram)
+ return
[PATCH v4] mmap_vmcore: skip non-ram pages reported by hypervisors
We have a special check in read_vmcore() handler to check if the page was
reported as ram or not by the hypervisor (pfn_is_ram()). However, when
vmcore is read with mmap() no such check is performed. That can lead to
unpredictable results, e.g. when running Xen PVHVM guest memcpy() after
mmap() on /proc/vmcore will hang processing HVMMEM_mmio_dm pages creating
enormous load in both DomU and Dom0.
Fix the issue by mapping each non-ram page to the zero page. Keep direct
path with remap_oldmem_pfn_range() to avoid looping through all pages on
bare metal.
The issue can also be solved by overriding remap_oldmem_pfn_range() in
xen-specific code, as remap_oldmem_pfn_range() was been designed for.
That, however, would involve non-obvious xen code path for all x86 builds
with CONFIG_XEN_PVHVM=y and would prevent all other hypervisor-specific
code on x86 arch from doing the same override.
Changes from v3:
- multi line comment style changes
- minor code style changes
Changes from v2:
- make remap_oldmem_pfn_checked() interface exactly match
remap_oldmem_pfn_range()
- unmap mapped part inside remap_oldmem_pfn_checked() in case of failure so
we don't need to take care of it in mmap_vmcore()
- create vmcore_remap_oldmem_pfn() wrapper
Changes from v1:
- comment style changes
- change remap_oldmem_pfn_checked() interface to closer match the
remap_oldmem_pfn() interface
- preserve formal parameters within the loop, make the loop conditions
easier to understand
- use my_zero_pfn() for the zero page
- return remapped length instead of new offset
Signed-off-by: Vitaly Kuznetsov vkuzn...@redhat.com
Reviewed-by: Andrew Jones drjo...@redhat.com
---
fs/proc/vmcore.c | 83 ++--
1 file changed, 80 insertions(+), 3 deletions(-)
diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index 382aa89..405a409 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -328,6 +328,83 @@ static inline char *alloc_elfnotes_buf(size_t notes_sz)
* virtually contiguous user-space in ELF layout.
*/
#ifdef CONFIG_MMU
+/*
+ * remap_oldmem_pfn_checked - do remap_oldmem_pfn_range replacing all pages
+ * reported as not being ram with the zero page.
+ *
+ * @vma: vm_area_struct describing requested mapping
+ * @from: start remapping from
+ * @pfn: page frame number to start remapping to
+ * @size: remapping size
+ * @prot: protection bits
+ *
+ * Returns zero on success, -EAGAIN on failure.
+ */
+int remap_oldmem_pfn_checked(struct vm_area_struct *vma, unsigned long from,
+unsigned long pfn, unsigned long size,
+pgprot_t prot)
+{
+ size_t map_size;
+ unsigned long pos_start, pos_end, pos;
+ unsigned long zeropage_pfn = my_zero_pfn(0);
+ u64 len = 0;
+
+ pos_start = pfn;
+ pos_end = pfn + (size PAGE_SHIFT);
+
+ for (pos = pos_start; pos pos_end; ++pos) {
+ if (!pfn_is_ram(pos)) {
+ /*
+* We hit a page which is not ram. Remap the continuous
+* region between pos_start and pos-1 and replace
+* the non-ram page at pos with the zero page.
+*/
+ if (pos pos_start) {
+ /* Remap continuous region */
+ map_size = (pos - pos_start) PAGE_SHIFT;
+ if (remap_oldmem_pfn_range(vma, from + len,
+ pos_start, map_size,
+ prot))
+ goto fail;
+ len += map_size;
+ }
+ /* Remap the zero page */
+ if (remap_oldmem_pfn_range(vma, from + len,
+ zeropage_pfn,
+ PAGE_SIZE, prot))
+ goto fail;
+ len += PAGE_SIZE;
+ pos_start = pos + 1;
+ }
+ }
+ if (pos pos_start) {
+ /* Remap the rest */
+ map_size = (pos - pos_start) PAGE_SHIFT;
+ if (remap_oldmem_pfn_range(vma, from + len, pos_start,
+ map_size, vma-vm_page_prot))
+ goto fail;
+ len += map_size;
+ }
+ return 0;
+fail:
+ do_munmap(vma-vm_mm, from, len);
+ return -EAGAIN;
+}
+
+int vmcore_remap_oldmem_pfn(struct vm_area_struct *vma,
+ unsigned long from, unsigned long pfn,
+ unsigned long size, pgprot_t prot)
+{
+ /*
+* Check if oldmem_pfn_is_ram was registered to avoid
+* looping over all pages without a reason.
+*/
+ if (oldmem_pfn_is_ram)
+
Re: [PATCH v4] mmap_vmcore: skip non-ram pages reported by hypervisors
On Fri, Jul 11, 2014 at 10:49:12AM +0200, Vitaly Kuznetsov wrote:
We have a special check in read_vmcore() handler to check if the page was
reported as ram or not by the hypervisor (pfn_is_ram()). However, when
vmcore is read with mmap() no such check is performed. That can lead to
unpredictable results, e.g. when running Xen PVHVM guest memcpy() after
mmap() on /proc/vmcore will hang processing HVMMEM_mmio_dm pages creating
enormous load in both DomU and Dom0.
Fix the issue by mapping each non-ram page to the zero page. Keep direct
path with remap_oldmem_pfn_range() to avoid looping through all pages on
bare metal.
The issue can also be solved by overriding remap_oldmem_pfn_range() in
xen-specific code, as remap_oldmem_pfn_range() was been designed for.
That, however, would involve non-obvious xen code path for all x86 builds
with CONFIG_XEN_PVHVM=y and would prevent all other hypervisor-specific
code on x86 arch from doing the same override.
Changes from v3:
- multi line comment style changes
- minor code style changes
Changes from v2:
- make remap_oldmem_pfn_checked() interface exactly match
remap_oldmem_pfn_range()
- unmap mapped part inside remap_oldmem_pfn_checked() in case of failure so
we don't need to take care of it in mmap_vmcore()
- create vmcore_remap_oldmem_pfn() wrapper
Changes from v1:
- comment style changes
- change remap_oldmem_pfn_checked() interface to closer match the
remap_oldmem_pfn() interface
- preserve formal parameters within the loop, make the loop conditions
easier to understand
- use my_zero_pfn() for the zero page
- return remapped length instead of new offset
Signed-off-by: Vitaly Kuznetsov vkuzn...@redhat.com
Reviewed-by: Andrew Jones drjo...@redhat.com
This one looks good to me. Thanks.
Acked-by: Vivek Goyal vgo...@redhat.com
Vivek
---
fs/proc/vmcore.c | 83
++--
1 file changed, 80 insertions(+), 3 deletions(-)
diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index 382aa89..405a409 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -328,6 +328,83 @@ static inline char *alloc_elfnotes_buf(size_t notes_sz)
* virtually contiguous user-space in ELF layout.
*/
#ifdef CONFIG_MMU
+/*
+ * remap_oldmem_pfn_checked - do remap_oldmem_pfn_range replacing all pages
+ * reported as not being ram with the zero page.
+ *
+ * @vma: vm_area_struct describing requested mapping
+ * @from: start remapping from
+ * @pfn: page frame number to start remapping to
+ * @size: remapping size
+ * @prot: protection bits
+ *
+ * Returns zero on success, -EAGAIN on failure.
+ */
+int remap_oldmem_pfn_checked(struct vm_area_struct *vma, unsigned long from,
+ unsigned long pfn, unsigned long size,
+ pgprot_t prot)
+{
+ size_t map_size;
+ unsigned long pos_start, pos_end, pos;
+ unsigned long zeropage_pfn = my_zero_pfn(0);
+ u64 len = 0;
+
+ pos_start = pfn;
+ pos_end = pfn + (size PAGE_SHIFT);
+
+ for (pos = pos_start; pos pos_end; ++pos) {
+ if (!pfn_is_ram(pos)) {
+ /*
+ * We hit a page which is not ram. Remap the continuous
+ * region between pos_start and pos-1 and replace
+ * the non-ram page at pos with the zero page.
+ */
+ if (pos pos_start) {
+ /* Remap continuous region */
+ map_size = (pos - pos_start) PAGE_SHIFT;
+ if (remap_oldmem_pfn_range(vma, from + len,
+pos_start, map_size,
+prot))
+ goto fail;
+ len += map_size;
+ }
+ /* Remap the zero page */
+ if (remap_oldmem_pfn_range(vma, from + len,
+zeropage_pfn,
+PAGE_SIZE, prot))
+ goto fail;
+ len += PAGE_SIZE;
+ pos_start = pos + 1;
+ }
+ }
+ if (pos pos_start) {
+ /* Remap the rest */
+ map_size = (pos - pos_start) PAGE_SHIFT;
+ if (remap_oldmem_pfn_range(vma, from + len, pos_start,
+map_size, vma-vm_page_prot))
+ goto fail;
+ len += map_size;
+ }
+ return 0;
+fail:
+ do_munmap(vma-vm_mm, from, len);
+ return -EAGAIN;
+}
+
+int vmcore_remap_oldmem_pfn(struct vm_area_struct *vma,
+ unsigned long from, unsigned long pfn,
+ unsigned long size, pgprot_t prot)
+{
+
