| Message ID | e8863e289577e0dc1e365b5419bf2d1c9a24ae3d.1729218573.git.baolin.wang@linux.alibaba.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Improve the tmpfs large folio read performance | expand |
On Thu, Oct 17, 2024 at 8:00 PM Baolin Wang <baolin.wang@linux.alibaba.com> wrote: > > 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 s/performace/performance > in the following patch. > > Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com> The patch looks good to me. Reviewed-by: Yang Shi <shy828301@gmail.com> > --- > mm/shmem.c | 35 +++++++++++------------------------ > 1 file changed, 11 insertions(+), 24 deletions(-) > > diff --git a/mm/shmem.c b/mm/shmem.c > index 66eae800ffab..93642aa8d1aa 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -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; > } > -- > 2.39.3 >
diff --git a/mm/shmem.c b/mm/shmem.c index 66eae800ffab..93642aa8d1aa 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -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(-)