@@ -3106,27 +3106,19 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
unsigned long offset;
int error = 0;
ssize_t retval = 0;
- loff_t *ppos = &iocb->ki_pos;
- index = *ppos >> PAGE_SHIFT;
- offset = *ppos & ~PAGE_MASK;
+ offset = iocb->ki_pos & ~PAGE_MASK;
for (;;) {
struct folio *folio = NULL;
struct page *page = NULL;
- pgoff_t end_index;
unsigned long nr, ret;
- loff_t i_size = i_size_read(inode);
+ loff_t end_offset, i_size = i_size_read(inode);
- end_index = i_size >> PAGE_SHIFT;
- if (index > end_index)
+ if (unlikely(iocb->ki_pos >= i_size))
break;
- if (index == end_index) {
- nr = i_size & ~PAGE_MASK;
- if (nr <= offset)
- break;
- }
+ index = iocb->ki_pos >> PAGE_SHIFT;
error = shmem_get_folio(inode, index, 0, &folio, SGP_READ);
if (error) {
if (error == -EINVAL)
@@ -3148,18 +3140,14 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
* We must evaluate after, since reads (unlike writes)
* are called without i_rwsem protection against truncate
*/
- nr = PAGE_SIZE;
i_size = i_size_read(inode);
- end_index = i_size >> PAGE_SHIFT;
- if (index == end_index) {
- nr = i_size & ~PAGE_MASK;
- if (nr <= offset) {
- if (folio)
- folio_put(folio);
- break;
- }
+ if (unlikely(iocb->ki_pos >= i_size)) {
+ if (folio)
+ folio_put(folio);
+ break;
}
- nr -= offset;
+ end_offset = min_t(loff_t, i_size, iocb->ki_pos + to->count);
+ nr = min_t(loff_t, end_offset - iocb->ki_pos, PAGE_SIZE - offset);
if (folio) {
/*
@@ -3199,8 +3187,8 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
retval += ret;
offset += ret;
- index += offset >> PAGE_SHIFT;
offset &= ~PAGE_MASK;
+ iocb->ki_pos += ret;
if (!iov_iter_count(to))
break;
@@ -3211,7 +3199,6 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
cond_resched();
}
- *ppos = ((loff_t) index << PAGE_SHIFT) + offset;
file_accessed(file);
return retval ? retval : error;
}
Use iocb->ki_pos to check if the read bytes exceeds the file size and to calculate the bytes to be read can help simplify the code logic. Meanwhile, this is also a preparation for improving tmpfs large folios read performace in the following patch. Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com> --- mm/shmem.c | 35 +++++++++++------------------------ 1 file changed, 11 insertions(+), 24 deletions(-)