TechPanelGM/kernel_xiaomi_sm8250
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

kernfs: implement kernfs_ops->atomic_write_len

Browse Source 
A write to a kernfs_node is buffered through a kernel buffer.  Writes
<= PAGE_SIZE are performed atomically, while larger ones are executed
in PAGE_SIZE chunks.  While this is enough for sysfs, cgroup which is
scheduled to be converted to use kernfs needs a bit more control over
it.

This patch adds kernfs_ops->atomic_write_len.  If not set (zero), the
behavior stays the same.  If set, writes upto the size are executed
atomically and larger writes are rejected with -E2BIG.

A different implementation strategy would be allowing configuring
chunking size while making the original write size available to the
write method; however, such strategy, while being more complicated,
doesn't really buy anything.  If the write implementation has to
handle chunking, the specific chunk size shouldn't matter all that
much.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Tejun Heo
2014-02-03 14:09:13 -05:00
committed by Greg Kroah-Hartman
parent d35258ef70
commit 4d3773c4bb
2 changed files with 37 additions and 20 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
include/linux/kernfs.h
View File

@@ -178,9 +178,13 @@ struct kernfs_ops {
loff_t off);
/*
* write() is bounced through kernel buffer and a write larger than
* PAGE_SIZE results in partial operation of PAGE_SIZE.
* write() is bounced through kernel buffer. If atomic_write_len
* is not set, a write larger than PAGE_SIZE results in partial
* operations of PAGE_SIZE chunks. If atomic_write_len is set,
* writes upto the specified size are executed atomically but
* larger ones are rejected with -E2BIG.
*/
size_t atomic_write_len;
ssize_t (*write)(struct kernfs_open_file *of, char *buf, size_t bytes,
loff_t off);