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Subject[patch -v2 13/23] introduce memory_read_from_buffer
This patch introduces memory_read_from_buffer.

The only difference between memory_read_from_buffer and simple_read_from_buffer
is which address space the function copies to.

simple_read_from_buffer copies to user space memory.
memory_read_from_buffer copies to normal memory.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
---
fs/libfs.c | 18 ++++++++++++++++++
include/linux/fs.h | 5 ++++-
2 files changed, 22 insertions(+), 1 deletion(-)
Index: 2.6-git/fs/libfs.c
===================================================================
--- 2.6-git.orig/fs/libfs.c
+++ 2.6-git/fs/libfs.c
@@ -528,6 +528,23 @@ ssize_t simple_read_from_buffer(void __u
return count;
}

+ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
+ const void *from, size_t available)
+{
+ loff_t pos = *ppos;
+
+ if (pos < 0)
+ return -EINVAL;
+ if (pos >= available)
+ return 0;
+ if (count > available - pos)
+ count = available - pos;
+ memcpy(to, from + pos, count);
+ *ppos = pos + count;
+
+ return count;
+}
+
/*
* Transaction based IO.
* The file expects a single write which triggers the transaction, and then
@@ -800,6 +817,7 @@ EXPORT_SYMBOL(simple_statfs);
EXPORT_SYMBOL(simple_sync_file);
EXPORT_SYMBOL(simple_unlink);
EXPORT_SYMBOL(simple_read_from_buffer);
+EXPORT_SYMBOL(memory_read_from_buffer);
EXPORT_SYMBOL(simple_transaction_get);
EXPORT_SYMBOL(simple_transaction_read);
EXPORT_SYMBOL(simple_transaction_release);
Index: 2.6-git/include/linux/fs.h
===================================================================
--- 2.6-git.orig/include/linux/fs.h
+++ 2.6-git/include/linux/fs.h
@@ -2000,7 +2000,10 @@ extern int simple_fill_super(struct supe
extern int simple_pin_fs(struct file_system_type *, struct vfsmount **mount, int *count);
extern void simple_release_fs(struct vfsmount **mount, int *count);

-extern ssize_t simple_read_from_buffer(void __user *, size_t, loff_t *, const void *, size_t);
+extern ssize_t simple_read_from_buffer(void __user *to, size_t count,
+ loff_t *ppos, const void *from, size_t available);
+extern ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
+ const void *from, size_t available);

#ifdef CONFIG_MIGRATION
extern int buffer_migrate_page(struct address_space *,
--


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