@@ -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.
-*/
-#define MAX_KMALLOC_SIZE 0x20000
+/* Back in April 2005, Linus 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_alloc_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 Linus 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.
+ */
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_alloc_up_to(&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_alloc_up_to(&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);
@@ -638,6 +638,36 @@ int default_mtd_writev(struct mtd_info *mtd, const struct kvec *vecs,
return ret;
}
+/* mtd_alloc_up_to - called, for example by mtd_{read,write} and
+ * jffs2_scan_medium, to handle smaller (i.e. degraded) buffer
+ * allocations under low- or fragmented-memory situations where
+ * such reduced allocations, from a requested ideal, are allowed.
+ */
+
+#define MAX_KMALLOC_SIZE 0x20000
+
+void *mtd_alloc_up_to(size_t *size)
+{
+ gfp_t flags;
+ size_t try;
+ void *kbuf;
+
+ try = min_t(size_t, *size, MAX_KMALLOC_SIZE);
+
+ do {
+ flags = ((size == PAGE_SIZE) ?
+ GFP_KERNEL :
+ (__GFP_NOWARN | __GFP_WAIT |
+ __GFP_NORETRY | __GFP_NO_KSWAPD));
+
+ kbuf = kmalloc(try, flags);
+ } while (!kbuf && ((try >>= 1) >= PAGE_SIZE));
+
+ *size = try;
+
+ return kbuf;
+}
+
EXPORT_SYMBOL_GPL(add_mtd_device);
EXPORT_SYMBOL_GPL(del_mtd_device);
EXPORT_SYMBOL_GPL(get_mtd_device);
@@ -648,6 +678,7 @@ EXPORT_SYMBOL_GPL(__put_mtd_device);
EXPORT_SYMBOL_GPL(register_mtd_user);
EXPORT_SYMBOL_GPL(unregister_mtd_user);
EXPORT_SYMBOL_GPL(default_mtd_writev);
+EXPORT_SYMBOL_GPL(mtd_alloc_up_to);
#ifdef CONFIG_PROC_FS
@@ -117,14 +117,15 @@ int jffs2_scan_medium(struct jffs2_sb_info *c)
else
buf_size = PAGE_SIZE;
- /* Respect kmalloc limitations */
- if (buf_size > 128*1024)
- buf_size = 128*1024;
+ D1(printk(KERN_DEBUG "Trying to allocate readbuf of %d "
+ "bytes\n", buf_size));
- D1(printk(KERN_DEBUG "Allocating readbuf of %d bytes\n", buf_size));
- flashbuf = kmalloc(buf_size, GFP_KERNEL);
+ flashbuf = mtd_alloc_up_to(&buf_size);
if (!flashbuf)
return -ENOMEM;
+
+ D1(printk(KERN_DEBUG "Allocated readbuf of %d bytes\n",
+ buf_size));
}
if (jffs2_sum_active()) {
@@ -348,7 +348,8 @@ int default_mtd_writev(struct mtd_info *mtd, const struct kvec *vecs,
int default_mtd_readv(struct mtd_info *mtd, struct kvec *vecs,
unsigned long count, loff_t from, size_t *retlen);
+void *mtd_alloc_up_to(size_t *size);
+
#ifdef CONFIG_MTD_PARTITIONS
void mtd_erase_callback(struct erase_info *instr);
#else
--