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/proc/stat: convert to single_open_size()

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These two patches are supposed to "fix" failed order-4 memory
allocations which have been observed when reading /proc/stat.  The
problem has been observed on s390 as well as on x86.

To address the problem change the seq_file memory allocations to
fallback to use vmalloc, so that allocations also work if memory is
fragmented.

This approach seems to be simpler and less intrusive than changing
/proc/stat to use an interator.  Also it "fixes" other users as well,
which use seq_file's single_open() interface.

This patch (of 2):

Use seq_file's single_open_size() to preallocate a buffer that is large
enough to hold the whole output, instead of open coding it.  Also
calculate the requested size using the number of online cpus instead of
possible cpus, since the size of the output only depends on the number
of online cpus.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Ian Kent <raven@themaw.net>
Cc: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Cc: Thorsten Diehl <thorsten.diehl@de.ibm.com>
Cc: Andrea Righi <andrea@betterlinux.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Stefan Bader <stefan.bader@canonical.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Heiko Carstens 2014-07-02 15:22:37 -07:00 committed by Linus Torvalds
parent 0bc1f8b068
commit f74373a5cc
1 changed files with 2 additions and 20 deletions
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22
fs/proc/stat.c
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@ -184,29 +184,11 @@ static int show_stat(struct seq_file *p, void *v)
static int stat_open(struct inode *inode, struct file *file) static int stat_open(struct inode *inode, struct file *file)
{ {
size_t size = 1024 + 128 * num_possible_cpus(); size_t size = 1024 + 128 * num_online_cpus();
char *buf;
struct seq_file *m;
int res;
/* minimum size to display an interrupt count : 2 bytes */ /* minimum size to display an interrupt count : 2 bytes */
size += 2 * nr_irqs; size += 2 * nr_irqs;
return single_open_size(file, show_stat, NULL, size);
/* don't ask for more than the kmalloc() max size */
if (size > KMALLOC_MAX_SIZE)
size = KMALLOC_MAX_SIZE;
buf = kmalloc(size, GFP_KERNEL);
if (!buf)
return -ENOMEM;
res = single_open(file, show_stat, NULL);
if (!res) {
m = file->private_data;
m->buf = buf;
m->size = ksize(buf);
} else
kfree(buf);
return res;
} }
static const struct file_operations proc_stat_operations = { static const struct file_operations proc_stat_operations = {