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Subject[PATCH 13/23] fs: don't change the address limit for ->read_iter in __kernel_read
Date
If we read to a file that implements ->read_iter there is no need
to change the address limit if we send a kvec down.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
fs/read_write.c | 40 +++++++++++++++++++++++++---------------
1 file changed, 25 insertions(+), 15 deletions(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index 6a2170eaee64f9..8bec4418543994 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -421,7 +421,6 @@ static ssize_t new_sync_read(struct file *filp, char __user *buf, size_t len, lo

ssize_t __kernel_read(struct file *file, void *buf, size_t count, loff_t *pos)
{
- mm_segment_t old_fs = get_fs();
ssize_t ret;

if (WARN_ON_ONCE(!(file->f_mode & FMODE_READ)))
@@ -431,14 +430,25 @@ ssize_t __kernel_read(struct file *file, void *buf, size_t count, loff_t *pos)

if (count > MAX_RW_COUNT)
count = MAX_RW_COUNT;
- set_fs(KERNEL_DS);
- if (file->f_op->read)
+ if (file->f_op->read) {
+ mm_segment_t old_fs = get_fs();
+
+ set_fs(KERNEL_DS);
ret = file->f_op->read(file, (void __user *)buf, count, pos);
- else if (file->f_op->read_iter)
- ret = new_sync_read(file, (void __user *)buf, count, pos);
- else
+ set_fs(old_fs);
+ } else if (file->f_op->read_iter) {
+ struct kvec iov = { .iov_base = buf, .iov_len = count };
+ struct kiocb kiocb;
+ struct iov_iter iter;
+
+ init_sync_kiocb(&kiocb, file);
+ kiocb.ki_pos = *pos;
+ iov_iter_kvec(&iter, READ, &iov, 1, count);
+ ret = file->f_op->read_iter(&kiocb, &iter);
+ *pos = kiocb.ki_pos;
+ } else {
ret = -EINVAL;
- set_fs(old_fs);
+ }
if (ret > 0) {
fsnotify_access(file);
add_rchar(current, ret);
@@ -520,7 +530,14 @@ ssize_t __kernel_write(struct file *file, const void *buf, size_t count,

if (count > MAX_RW_COUNT)
count = MAX_RW_COUNT;
- if (file->f_op->write_iter) {
+ if (file->f_op->write) {
+ mm_segment_t old_fs = get_fs();
+
+ set_fs(KERNEL_DS);
+ ret = file->f_op->write(file, (__force const char __user *)buf,
+ count, pos);
+ set_fs(old_fs);
+ } else if (file->f_op->write_iter) {
struct kvec iov = { .iov_base = (void *)buf, .iov_len = count };
struct kiocb kiocb;
struct iov_iter iter;
@@ -531,13 +548,6 @@ ssize_t __kernel_write(struct file *file, const void *buf, size_t count,
ret = file->f_op->write_iter(&kiocb, &iter);
if (ret > 0)
*pos = kiocb.ki_pos;
- } else if (file->f_op->write) {
- mm_segment_t old_fs = get_fs();
-
- set_fs(KERNEL_DS);
- ret = file->f_op->write(file, (__force const char __user *)buf,
- count, pos);
- set_fs(old_fs);
} else {
ret = -EINVAL;
}
--
2.26.2
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