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Commit 3e45cf5e authored by Grant Erickson's avatar Grant Erickson Committed by David Woodhouse
Browse files

mtd: mtdchar: retry large buffer allocations 



Replace direct call to kmalloc for a potentially large, contiguous
buffer allocation with one to mtd_kmalloc_up_to which helps ensure the
operation can succeed under low-memory, highly- fragmented situations
albeit somewhat more slowly.

Signed-off-by: default avatarGrant Erickson <marathon96@gmail.com>
Tested-by: default avatarBen Gardiner <bengardiner@nanometrics.ca>
Tested-by: default avatarStefano Babic <sbabic@denx.de>
Signed-off-by: default avatarArtem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: default avatarDavid Woodhouse <David.Woodhouse@intel.com>
parent 33b53716

drivers/mtd/mtdchar.c

+23 −27
Original line number Diff line number Diff line
@@ -166,10 +166,23 @@ static int mtd_close(struct inode *inode, struct file *file) 
	return 0;

} /* mtd_close */



/* FIXME: This _really_ needs to die. In 2.5, we should lock the

   userspace buffer down and use it directly with readv/writev.

/* Back in June 2001, dwmw2 wrote:

 *

 *   FIXME: This _really_ needs to die. In 2.5, we should lock the

 *   userspace buffer down and use it directly with readv/writev.

 *

 * The implementation below, using mtd_kmalloc_up_to, mitigates

 * allocation failures when the system is under low-memory situations

 * or if memory is highly fragmented at the cost of reducing the

 * performance of the requested transfer due to a smaller buffer size.

 *

 * A more complex but more memory-efficient implementation based on

 * get_user_pages and iovecs to cover extents of those pages is a

 * longer-term goal, as intimated by dwmw2 above. However, for the

 * write case, this requires yet more complex head and tail transfer

 * handling when those head and tail offsets and sizes are such that

 * alignment requirements are not met in the NAND subdriver.

 */

#define MAX_KMALLOC_SIZE 0x20000



static ssize_t mtd_read(struct file *file, char __user *buf, size_t count,loff_t *ppos)

{
@@ -179,6 +192,7 @@ static ssize_t mtd_read(struct file *file, char __user *buf, size_t count,loff_t 
	size_t total_retlen=0;

	int ret=0;

	int len;

	size_t size = count;

	char *kbuf;



	DEBUG(MTD_DEBUG_LEVEL0,"MTD_read\n");
@@ -189,23 +203,12 @@ static ssize_t mtd_read(struct file *file, char __user *buf, size_t count,loff_t 
	if (!count)

		return 0;



	/* FIXME: Use kiovec in 2.5 to lock down the user's buffers

	   and pass them directly to the MTD functions */



	if (count > MAX_KMALLOC_SIZE)

		kbuf=kmalloc(MAX_KMALLOC_SIZE, GFP_KERNEL);

	else

		kbuf=kmalloc(count, GFP_KERNEL);



	kbuf = mtd_kmalloc_up_to(mtd, &size);

	if (!kbuf)

		return -ENOMEM;



	while (count) {



		if (count > MAX_KMALLOC_SIZE)

			len = MAX_KMALLOC_SIZE;

		else

			len = count;

		len = min_t(size_t, count, size);



		switch (mfi->mode) {

		case MTD_MODE_OTP_FACTORY:
@@ -268,6 +271,7 @@ static ssize_t mtd_write(struct file *file, const char __user *buf, size_t count 
{

	struct mtd_file_info *mfi = file->private_data;

	struct mtd_info *mtd = mfi->mtd;

	size_t size = count;

	char *kbuf;

	size_t retlen;

	size_t total_retlen=0;
@@ -285,20 +289,12 @@ static ssize_t mtd_write(struct file *file, const char __user *buf, size_t count 
	if (!count)

		return 0;



	if (count > MAX_KMALLOC_SIZE)

		kbuf=kmalloc(MAX_KMALLOC_SIZE, GFP_KERNEL);

	else

		kbuf=kmalloc(count, GFP_KERNEL);



	kbuf = mtd_kmalloc_up_to(mtd, &size);

	if (!kbuf)

		return -ENOMEM;



	while (count) {



		if (count > MAX_KMALLOC_SIZE)

			len = MAX_KMALLOC_SIZE;

		else

			len = count;

		len = min_t(size_t, count, size);



		if (copy_from_user(kbuf, buf, len)) {

			kfree(kbuf);