Fix the fault-in window size logic:
* Use a maximum window size of 1 MiB instead of BIO_MAX_VECS * PAGE_SIZE.
The previous window size was always one page because the pages variable
was accidentally being redefined in should_fault_in_pages().
* Account for page overlap (unaligned iterators).
* The nr_dirtied heuristic for guessing when there might be memory
pressure often results in very window sizes. Don't let nr_dirtied
drop below 8 pages (as btrfs does).
* Compute the window size in units of bytes, not pages.
Signed-off-by: Andreas Gruenbacher <agrue...@redhat.com>
---
fs/gfs2/file.c | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)
diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index a743a9eb602f..ac0665a70d46 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -775,8 +775,7 @@ static inline bool should_fault_in_pages(ssize_t ret,
struct iov_iter *i,
size_t *window_size)
{
size_t count = iov_iter_count(i);
- char __user *p;
- int pages = 1;
+ size_t size, offs;
if (likely(!count))
return false;
@@ -785,18 +784,20 @@ static inline bool should_fault_in_pages(ssize_t ret,
struct iov_iter *i,
if (!iter_is_iovec(i))
return false;
+ size = PAGE_SIZE;
+ offs = offset_in_page(i->iov[0].iov_base + i->iov_offset);
if (*prev_count != count || !*window_size) {
- int pages, nr_dirtied;
+ int nr_dirtied;
- pages = min_t(int, BIO_MAX_VECS, DIV_ROUND_UP(count,
PAGE_SIZE));
+ size = ALIGN(offs + count, PAGE_SIZE);
+ size = min_t(size_t, size, SZ_1M);
nr_dirtied = max(current->nr_dirtied_pause -
- current->nr_dirtied, 1);
- pages = min(pages, nr_dirtied);
+ current->nr_dirtied, 8);
+ size = min(size, nr_dirtied << PAGE_SHIFT);
}
*prev_count = count;
- p = i->iov[0].iov_base + i->iov_offset;
- *window_size = (size_t)PAGE_SIZE * pages - offset_in_page(p);
+ *window_size = size - offs;
return true;
}
--
2.33.1
