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mm, mempolicy: make mpol_to_str robust and always succeed

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mpol_to_str() should not fail.  Currently, it either fails because the
string buffer is too small or because a string hasn't been defined for a
mempolicy mode.

If a new mempolicy mode is introduced and no string is defined for it,
just warn and return "unknown".

If the buffer is too small, just truncate the string and return, the
same behavior as snprintf().

This also fixes a bug where there was no NULL-byte termination when doing
*p++ = '=' and *p++ ':' and maxlen has been reached.

Signed-off-by: David Rientjes <rientjes@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Chen Gang <gang.chen@asianux.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Dave Jones <davej@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Rientjes 2013-11-12 15:07:28 -08:00 committed by Linus Torvalds
parent 40c3baa7c6
commit 948927ee9e
3 changed files with 24 additions and 47 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
fs/proc/task_mmu.c
View File

@ -1387,8 +1387,8 @@ static int show_numa_map(struct seq_file *m, void *v, int is_pid)
struct mm_struct *mm = vma->vm_mm;
struct mm_walk walk = {};
struct mempolicy *pol;
int n;
char buffer[50];
char buffer[64];
int nid;
if (!mm)
return 0;
@ -1404,10 +1404,8 @@ static int show_numa_map(struct seq_file *m, void *v, int is_pid)
walk.mm = mm;
pol = get_vma_policy(task, vma, vma->vm_start);
n = mpol_to_str(buffer, sizeof(buffer), pol);
mpol_to_str(buffer, sizeof(buffer), pol);
mpol_cond_put(pol);
if (n < 0)
return n;
seq_printf(m, "%08lx %s", vma->vm_start, buffer);
@ -1460,9 +1458,9 @@ static int show_numa_map(struct seq_file *m, void *v, int is_pid)
if (md->writeback)
seq_printf(m, " writeback=%lu", md->writeback);
for_each_node_state(n, N_MEMORY)
if (md->node[n])
seq_printf(m, " N%d=%lu", n, md->node[n]);
for_each_node_state(nid, N_MEMORY)
if (md->node[nid])
seq_printf(m, " N%d=%lu", nid, md->node[nid]);
out:
seq_putc(m, '\n');

5
include/linux/mempolicy.h
View File

@ -169,7 +169,7 @@ int do_migrate_pages(struct mm_struct *mm, const nodemask_t *from,
extern int mpol_parse_str(char *str, struct mempolicy **mpol);
#endif
extern int mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol);
extern void mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol);
/* Check if a vma is migratable */
static inline int vma_migratable(struct vm_area_struct *vma)
@ -307,9 +307,8 @@ static inline int mpol_parse_str(char *str, struct mempolicy **mpol)
}
#endif
static inline int mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)
static inline void mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)
{
return 0;
}
static inline int mpol_misplaced(struct page *page, struct vm_area_struct *vma,

52
mm/mempolicy.c
View File

@ -2914,62 +2914,45 @@ int mpol_parse_str(char *str, struct mempolicy **mpol)
* @maxlen: length of @buffer
* @pol: pointer to mempolicy to be formatted
*
* Convert a mempolicy into a string.
* Returns the number of characters in buffer (if positive)
* or an error (negative)
* Convert @pol into a string. If @buffer is too short, truncate the string.
* Recommend a @maxlen of at least 32 for the longest mode, "interleave", the
* longest flag, "relative", and to display at least a few node ids.
*/
int mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)
void mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)
{
char *p = buffer;
int l;
nodemask_t nodes;
unsigned short mode;
unsigned short flags = pol ? pol->flags : 0;
nodemask_t nodes = NODE_MASK_NONE;
unsigned short mode = MPOL_DEFAULT;
unsigned short flags = 0;
/*
* Sanity check: room for longest mode, flag and some nodes
*/
VM_BUG_ON(maxlen < strlen("interleave") + strlen("relative") + 16);
if (!pol || pol == &default_policy)
mode = MPOL_DEFAULT;
else
if (pol && pol != &default_policy) {
mode = pol->mode;
flags = pol->flags;
}
switch (mode) {
case MPOL_DEFAULT:
nodes_clear(nodes);
break;
case MPOL_PREFERRED:
nodes_clear(nodes);
if (flags & MPOL_F_LOCAL)
mode = MPOL_LOCAL;
else
node_set(pol->v.preferred_node, nodes);
break;
case MPOL_BIND:
/* Fall through */
case MPOL_INTERLEAVE:
nodes = pol->v.nodes;
break;
default:
return -EINVAL;
WARN_ON_ONCE(1);
snprintf(p, maxlen, "unknown");
return;
}
l = strlen(policy_modes[mode]);
if (buffer + maxlen < p + l + 1)
return -ENOSPC;
strcpy(p, policy_modes[mode]);
p += l;
p += snprintf(p, maxlen, policy_modes[mode]);
if (flags & MPOL_MODE_FLAGS) {
if (buffer + maxlen < p + 2)
return -ENOSPC;
*p++ = '=';
p += snprintf(p, buffer + maxlen - p, "=");
/*
* Currently, the only defined flags are mutually exclusive
@ -2981,10 +2964,7 @@ int mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)
}
if (!nodes_empty(nodes)) {
if (buffer + maxlen < p + 2)
return -ENOSPC;
*p++ = ':';
p += snprintf(p, buffer + maxlen - p, ":");
p += nodelist_scnprintf(p, buffer + maxlen - p, nodes);
}
return p - buffer;
}