Commit 6a727b43 authored by Jiri Slaby's avatar Jiri Slaby Committed by Rafael J. Wysocki

FS / libfs: Implement simple_write_to_buffer

It will be used in suspend code and serves as an easy wrap around
copy_from_user. Similar to simple_read_from_buffer, it takes care
of transfers with proper lengths depending on available and count
parameters and advances ppos appropriately.
Signed-off-by: default avatarJiri Slaby <>
Signed-off-by: default avatarRafael J. Wysocki <>
parent bc6a0cbd
......@@ -546,6 +546,40 @@ ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
return count;
* simple_write_to_buffer - copy data from user space to the buffer
* @to: the buffer to write to
* @available: the size of the buffer
* @ppos: the current position in the buffer
* @from: the user space buffer to read from
* @count: the maximum number of bytes to read
* The simple_write_to_buffer() function reads up to @count bytes from the user
* space address starting at @from into the buffer @to at offset @ppos.
* On success, the number of bytes written is returned and the offset @ppos is
* advanced by this number, or negative value is returned on error.
ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
const void __user *from, size_t count)
loff_t pos = *ppos;
size_t res;
if (pos < 0)
return -EINVAL;
if (pos >= available || !count)
return 0;
if (count > available - pos)
count = available - pos;
res = copy_from_user(to + pos, from, count);
if (res == count)
return -EFAULT;
count -= res;
*ppos = pos + count;
return count;
* memory_read_from_buffer - copy data from the buffer
* @to: the kernel space buffer to read to
......@@ -864,6 +898,7 @@ EXPORT_SYMBOL(simple_statfs);
......@@ -2362,6 +2362,8 @@ extern void simple_release_fs(struct vfsmount **mount, int *count);
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 simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
const void __user *from, size_t count);
extern int simple_fsync(struct file *, struct dentry *, int);
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment