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

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 <jslaby@suse.cz>
Signed-off-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
parent bc6a0cbd

fs/libfs.c

+35 −0
Original line number Diff line number Diff line
@@ -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); 
EXPORT_SYMBOL(simple_sync_file);

EXPORT_SYMBOL(simple_unlink);

EXPORT_SYMBOL(simple_read_from_buffer);

EXPORT_SYMBOL(simple_write_to_buffer);

EXPORT_SYMBOL(memory_read_from_buffer);

EXPORT_SYMBOL(simple_transaction_set);

EXPORT_SYMBOL(simple_transaction_get);

include/linux/fs.h

+2 −0
Original line number Diff line number Diff line
@@ -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);