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Subject[PATCH 3/3] seq_file: convert seq buffer to vmalloc
Date
seq_files are often used for debugging.  When things are going wrong
due to failed physically contiguous allocations, the exponentially
growing physically contiguous allocations in seq_read can make things
worse. There is no need for physically contiguous memory, so switch
to virtually contiguous memory instead.

Signed-off-by: Colin Cross <ccross@android.com>
---
fs/seq_file.c | 23 ++++++++++-------------
1 files changed, 10 insertions(+), 13 deletions(-)

diff --git a/fs/seq_file.c b/fs/seq_file.c
index 8d9778c..7045656 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -9,6 +9,7 @@
#include <linux/module.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
+#include <linux/vmalloc.h>

#include <asm/uaccess.h>
#include <asm/page.h>
@@ -76,15 +77,11 @@ int seq_reserve(struct seq_file *m, size_t size)
{
void *buf;

- /* don't ask for more than the kmalloc() max size */
- if (size > KMALLOC_MAX_SIZE)
- size = KMALLOC_MAX_SIZE;
-
- buf = kmalloc(size, GFP_KERNEL);
+ buf = vmalloc(size);
if (!buf)
return -ENOMEM;

- kfree(m->buf);
+ vfree(m->buf);
m->buf = buf;
m->size = size;

@@ -106,7 +103,7 @@ static int traverse(struct seq_file *m, loff_t offset)
return 0;
}
if (!m->buf) {
- m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
+ m->buf = vmalloc(m->size = PAGE_SIZE);
if (!m->buf)
return -ENOMEM;
}
@@ -145,8 +142,8 @@ static int traverse(struct seq_file *m, loff_t offset)

Eoverflow:
m->op->stop(m, p);
- kfree(m->buf);
- m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
+ vfree(m->buf);
+ m->buf = vmalloc(m->size <<= 1);
return !m->buf ? -ENOMEM : -EAGAIN;
}

@@ -199,7 +196,7 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
m->version = file->f_version;
/* grab buffer if we didn't have one */
if (!m->buf) {
- m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
+ m->buf = vmalloc(m->size = PAGE_SIZE);
if (!m->buf)
goto Enomem;
}
@@ -239,8 +236,8 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
if (m->count < m->size)
goto Fill;
m->op->stop(m, p);
- kfree(m->buf);
- m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
+ vfree(m->buf);
+ m->buf = vmalloc(m->size <<= 1);
if (!m->buf)
goto Enomem;
m->count = 0;
@@ -355,7 +352,7 @@ EXPORT_SYMBOL(seq_lseek);
int seq_release(struct inode *inode, struct file *file)
{
struct seq_file *m = file->private_data;
- kfree(m->buf);
+ vfree(m->buf);
kfree(m);
return 0;
}
--
1.7.4.1


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