mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-09-14 06:35:12 +00:00
/dev/zero: also implement ->read
Christophe reported a major speedup due to avoiding the iov_iter overhead, so just add this trivial function. Note that /dev/zero already implements both an iter and non-iter writes so this just makes it more symmetric. Tested-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20200903155922.1111551-1-hch@lst.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
parent
261e7818f0
commit
99f667352f
1 changed files with 22 additions and 0 deletions
|
@ -726,6 +726,27 @@ static ssize_t read_iter_zero(struct kiocb *iocb, struct iov_iter *iter)
|
||||||
return written;
|
return written;
|
||||||
}
|
}
|
||||||
|
|
||||||
|
static ssize_t read_zero(struct file *file, char __user *buf,
|
||||||
|
size_t count, loff_t *ppos)
|
||||||
|
{
|
||||||
|
size_t cleared = 0;
|
||||||
|
|
||||||
|
while (count) {
|
||||||
|
size_t chunk = min_t(size_t, count, PAGE_SIZE);
|
||||||
|
|
||||||
|
if (clear_user(buf + cleared, chunk))
|
||||||
|
return cleared ? cleared : -EFAULT;
|
||||||
|
cleared += chunk;
|
||||||
|
count -= chunk;
|
||||||
|
|
||||||
|
if (signal_pending(current))
|
||||||
|
return cleared ? cleared : -ERESTARTSYS;
|
||||||
|
cond_resched();
|
||||||
|
}
|
||||||
|
|
||||||
|
return cleared;
|
||||||
|
}
|
||||||
|
|
||||||
static int mmap_zero(struct file *file, struct vm_area_struct *vma)
|
static int mmap_zero(struct file *file, struct vm_area_struct *vma)
|
||||||
{
|
{
|
||||||
#ifndef CONFIG_MMU
|
#ifndef CONFIG_MMU
|
||||||
|
@ -921,6 +942,7 @@ static const struct file_operations zero_fops = {
|
||||||
.llseek = zero_lseek,
|
.llseek = zero_lseek,
|
||||||
.write = write_zero,
|
.write = write_zero,
|
||||||
.read_iter = read_iter_zero,
|
.read_iter = read_iter_zero,
|
||||||
|
.read = read_zero,
|
||||||
.write_iter = write_iter_zero,
|
.write_iter = write_iter_zero,
|
||||||
.mmap = mmap_zero,
|
.mmap = mmap_zero,
|
||||||
.get_unmapped_area = get_unmapped_area_zero,
|
.get_unmapped_area = get_unmapped_area_zero,
|
||||||
|
|
Loading…
Reference in a new issue