swap: warn when a swap area overflows the maximum size

PATCH New Raymond Jennings 2 participants 7 messages Jul 7, 2013

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Memory management MM swap

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Raymond Jennings

author

2013-07-07 11:44 UTC #0 lore raw

PATCH 1/1 swap: warn when a swap area overflows the maximum size

swap: warn when a swap area overflows the maximum size

It is possible to swapon a swap area that is too big for the pte width to handle.

Presently this failure happens silently.

Instead, emit a diagnostic to warn the user.

Signed-off-by Raymond Jennings <[email protected]>

Acked-by Valdis Kletnieks <[email protected]>

----

mm/swapfile.c +0 -0

index 36af6ee..5a4ce53 100644
@@ -1953,6 +1953,12 @@ static unsigned long read_swap_header(struct

swap_info_struct *p,
*/
maxpages = swp_offset(pte_to_swp_entry(
swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
+ if (maxpages < swap_header->info.last_page) {
+ printk(KERN_WARNING
+ "Truncating oversized swap area, only using %luk out of %luk
\n",
+ maxpages << (PAGE_SHIFT - 10),
+ swap_header->info.last_page << (PAGE_SHIFT - 10));
+ }
if (maxpages > swap_header->info.last_page) {
maxpages = swap_header->info.last_page + 1; /* p->max is an unsigned int: don't overflow it */

----

Testing results, root prompt commands and kernel log messages:

# lvresize /dev/system/swap --size 16G
# mkswap /dev/system/swap
# swapon /dev/system/swap

Jul  7 04:27:22 warfang kernel: Adding 16777212k swap

on /dev/mapper/system-swap. Priority:-1 extents:1 across:16777212k

# lvresize /dev/system/swap --size 16G
# mkswap /dev/system/swap
# swapon /dev/system/swap

Jul  7 04:27:22 warfang kernel: Truncating oversized swap area, only
using 33554432k out of 67108860k
Jul  7 04:27:22 warfang kernel: Adding 33554428k swap

on /dev/mapper/system-swap. Priority:-1 extents:1 across:33554428k

Raymond Jennings

author

2013-07-07 11:53 UTC #1 lore raw

PATCH 1/1 swap: warn when a swap area overflows the maximum size (resent)

Silly me, wrong email address

On Sun, 2013-07-07 at 04:44 -0700, Raymond Jennings wrote:
swap: warn when a swap area overflows the maximum size

It is possible to swapon a swap area that is too big for the pte width to handle.

Presently this failure happens silently.

Instead, emit a diagnostic to warn the user.

Signed-off-by Raymond Jennings <[email protected]>

Acked-by Valdis Kletnieks <[email protected]>

----

mm/swapfile.c +0 -0

index 36af6ee..5a4ce53 100644
@@ -1953,6 +1953,12 @@ static unsigned long read_swap_header(struct

----

Testing results, root prompt commands and kernel log messages:

# lvresize /dev/system/swap --size 16G
# mkswap /dev/system/swap
# swapon /dev/system/swap

Jul  7 04:27:22 warfang kernel: Adding 16777212k swap

on /dev/mapper/system-swap. Priority:-1 extents:1 across:16777212k

# lvresize /dev/system/swap --size 16G
# mkswap /dev/system/swap
# swapon /dev/system/swap

Jul  7 04:27:22 warfang kernel: Truncating oversized swap area, only
using 33554432k out of 67108860k
Jul  7 04:27:22 warfang kernel: Adding 33554428k swap

on /dev/mapper/system-swap. Priority:-1 extents:1 across:33554428k

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Raymond Jennings

author

2013-07-07 11:59 UTC #2 lore raw

Re: [PATCH] swap: warn when a swap area overflows the maximum size (resent)

Typo in the second test.

The first line should read:

# lvresize /dev/system/swap --size 64G

First ever serious patch, got excited and burned the copypasta.

Raymond Jennings

author

2013-07-07 12:01 UTC #3 lore raw

Re: [PATCH] swap: warn when a swap area overflows the maximum size (resent)

In reply to Raymond Jennings

...I hate you gmail...

Quoted 1 line · Raymond Jennings

# lvresize /dev/system/swap --size 16G

Typo in the second test.

The first line should read:

# lvresize /dev/system/swap --size 64G

First ever serious patch, got excited and burned the copypasta.

Quoted 7 lines

# mkswap /dev/system/swap
# swapon /dev/system/swap

Jul  7 04:27:22 warfang kernel: Truncating oversized swap area, only
using 33554432k out of 67108860k
Jul  7 04:27:22 warfang kernel: Adding 33554428k swap

on /dev/mapper/system-swap. Priority:-1 extents:1 across:33554428k

Raymond Jennings

author

2013-07-07 19:13 UTC #4 lore raw

PATCH v2 1/1 swap: warn when a swap area overflows the maximum size

In reply to Raymond Jennings

Turned the comparison around for clarity of "bigger than"

No semantic changes, if it still compiles it should do the same thing so I've omitted the testing this time. Will be happy to retest if required but I'm on an atom 330 and kernel rebuilds are a nightmare.

----

swap: warn when a swap area overflows the maximum size

It is possible to swapon a swap area that is too big for the pte width to handle.

Presently this failure happens silently.

Instead, emit a diagnostic to warn the user.

Signed-off-by Raymond Jennings <[email protected]>

Acked-by Valdis Kletnieks <[email protected]>

----

mm/swapfile.c +0 -0

index 36af6ee..5a4ce53 100644
@@ -1953,6 +1953,12 @@ static unsigned long read_swap_header(struct

swap_info_struct *p,

         */
        maxpages = swp_offset(pte_to_swp_entry(
                        swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;

+ if (swap_header->info.last_page > maxpages) {
+ printk(KERN_WARNING
+ "Truncating oversized swap area, only using %luk
out of %luk
\n",
+ maxpages << (PAGE_SHIFT - 10),
+ swap_header->info.last_page << (PAGE_SHIFT -
10));
+ }

        if (maxpages > swap_header->info.last_page) {
                maxpages = swap_header->info.last_page + 1;
                /* p->max is an unsigned int: don't overflow it */

----

Testing results, root prompt commands and kernel log messages:

# lvresize /dev/system/swap --size 16G
# mkswap /dev/system/swap
# swapon /dev/system/swap

Jul  7 04:27:22 warfang kernel: Adding 16777212k swap

on /dev/mapper/system-swap. Priority:-1 extents:1 across:16777212k

# lvresize /dev/system/swap --size 16G
# mkswap /dev/system/swap
# swapon /dev/system/swap

Jul  7 04:27:22 warfang kernel: Truncating oversized swap area, only
using 33554432k out of 67108860k
Jul  7 04:27:22 warfang kernel: Adding 33554428k swap

on /dev/mapper/system-swap. Priority:-1 extents:1 across:33554428k

Rik van Riel

Reviewed-by on v2 1/1

2013-07-07 19:31 UTC #5 lore raw

Quoted 5 lines · Raymond Jennings

Turned the comparison around for clarity of "bigger than"
No semantic changes, if it still compiles it should do the same thing so I've omitted the testing this time. Will be happy to retest if required but I'm on an atom 330 and kernel rebuilds are a nightmare.

Added CC: Andrew Morton, since this should probably go into -mm :)

Quoted 7 lines

----
swap: warn when a swap area overflows the maximum size
It is possible to swapon a swap area that is too big for the pte width to handle.

Quoted 6 lines

Presently this failure happens silently.
Instead, emit a diagnostic to warn the user.
Signed-off-by Raymond Jennings <[email protected]>
Acked-by Valdis Kletnieks <[email protected]>

Reviewed-by Rik van Riel <[email protected]>

Quoted 43 lines

mm/swapfile.c +3 -0

index 36af6ee..5a4ce53 100644
@@ -1953,6 +1953,12 @@ static unsigned long read_swap_header(struct
 swap_info_struct *p,
          */
         maxpages = swp_offset(pte_to_swp_entry(
                         swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
+       if (swap_header->info.last_page > maxpages) {
+               printk(KERN_WARNING
+                      "Truncating oversized swap area, only using %luk

out of %luk
\n",

mm/swapfile.c +2 -0

+                      maxpages << (PAGE_SHIFT - 10),
+                      swap_header->info.last_page << (PAGE_SHIFT -

10));
+ }

         if (maxpages > swap_header->info.last_page) {
                 maxpages = swap_header->info.last_page + 1;
                 /* p->max is an unsigned int: don't overflow it */

----

Testing results, root prompt commands and kernel log messages:

# lvresize /dev/system/swap --size 16G
# mkswap /dev/system/swap
# swapon /dev/system/swap

Jul  7 04:27:22 warfang kernel: Adding 16777212k swap

on /dev/mapper/system-swap. Priority:-1 extents:1 across:16777212k

# lvresize /dev/system/swap --size 16G
# mkswap /dev/system/swap
# swapon /dev/system/swap

Jul  7 04:27:22 warfang kernel: Truncating oversized swap area, only
using 33554432k out of 67108860k
Jul  7 04:27:22 warfang kernel: Adding 33554428k swap

on /dev/mapper/system-swap. Priority:-1 extents:1 across:33554428k

Signature · 7 lines

All rights reversed

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Raymond Jennings

author

2013-07-07 20:56 UTC #6 lore raw

Screwed up and didn't attach my fixed test log to the second version.

See below.

Quoted 59 lines · Rik van Riel

Quoted 5 lines · Raymond Jennings
Turned the comparison around for clarity of "bigger than"
No semantic changes, if it still compiles it should do the same thing so I've omitted the testing this time. Will be happy to retest if required but I'm on an atom 330 and kernel rebuilds are a nightmare.
Added CC: Andrew Morton, since this should probably go into -mm :)
Quoted 7 lines
----
swap: warn when a swap area overflows the maximum size
It is possible to swapon a swap area that is too big for the pte width to handle.
Quoted 6 lines
Presently this failure happens silently.
Instead, emit a diagnostic to warn the user.
Signed-off-by Raymond Jennings <[email protected]>
Acked-by Valdis Kletnieks <[email protected]>
Reviewed-by Rik van Riel <[email protected]>
Quoted 34 lines
mm/swapfile.c +3 -0
index 36af6ee..5a4ce53 100644
@@ -1953,6 +1953,12 @@ static unsigned long read_swap_header(struct
 swap_info_struct *p,
          */
         maxpages = swp_offset(pte_to_swp_entry(
                         swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
+       if (swap_header->info.last_page > maxpages) {
+               printk(KERN_WARNING
+                      "Truncating oversized swap area, only using %luk
out of %luk
\n",
mm/swapfile.c +2 -0
+                      maxpages << (PAGE_SHIFT - 10),
+                      swap_header->info.last_page << (PAGE_SHIFT -
10));
+ }
         if (maxpages > swap_header->info.last_page) {
                 maxpages = swap_header->info.last_page + 1;
                 /* p->max is an unsigned int: don't overflow it */
----
Testing results, root prompt commands and kernel log messages:
# lvresize /dev/system/swap --size 16G
# mkswap /dev/system/swap
# swapon /dev/system/swap
Jul  7 04:27:22 warfang kernel: Adding 16777212k swap
on /dev/mapper/system-swap. Priority:-1 extents:1 across:16777212k
# lvresize /dev/system/swap --size 16G

Quoted 1 line · Raymond Jennings

# lvresize /dev/system/swap --size 16G

Typo in the second test.

The first line should read:

# lvresize /dev/system/swap --size 64G

First ever serious patch, got excited and burned the copypasta.

Quoted 14 lines

# mkswap /dev/system/swap
# swapon /dev/system/swap

Quoted 9 lines

# mkswap /dev/system/swap
# swapon /dev/system/swap

Jul  7 04:27:22 warfang kernel: Truncating oversized swap area, only
using 33554432k out of 67108860k
Jul  7 04:27:22 warfang kernel: Adding 33554428k swap

on /dev/mapper/system-swap. Priority:-1 extents:1 across:33554428k