In current implementation fuse_writepages_fill() tries to share the code:
for new wpa it calls tree_insert() with num_pages = 0
then switches to common code used non-modified num_pages
and increments it at the very end.
Though it triggers WARN_ON(!wpa->ia.ap.num_pages) in tree_insert()
WARNING: CPU: 1 PID: 17211 at fs/fuse/file.c:1728 tree_insert+0xab/0xc0 [fuse]
RIP: 0010:tree_insert+0xab/0xc0 [fuse]
Call Trace:
fuse_writepages_fill+0x5da/0x6a0 [fuse]
write_cache_pages+0x171/0x470
fuse_writepages+0x8a/0x100 [fuse]
do_writepages+0x43/0xe0
This patch re-works fuse_writepages_fill() to call tree_insert()
with num_pages = 1 and avoids its subsequent increment and
an extra spin_lock(&fi->lock) for newly added wpa.
Fixes: 6b2fb79963fb ("fuse: optimize writepages search")
Reported-by: kernel test robot <[email protected]>
Signed-off-by: Vasily Averin <[email protected]>
---
fs/fuse/file.c | 56 +++++++++++++++++++++++++++++---------------------------
1 file changed, 29 insertions(+), 27 deletions(-)
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index e573b0c..cf267bd 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1966,10 +1966,9 @@ static bool fuse_writepage_in_flight(struct
fuse_writepage_args *new_wpa,
struct fuse_writepage_args *old_wpa;
struct fuse_args_pages *new_ap = &new_wpa->ia.ap;
- WARN_ON(new_ap->num_pages != 0);
+ WARN_ON(new_ap->num_pages != 1);
spin_lock(&fi->lock);
- rb_erase(&new_wpa->writepages_entry, &fi->writepages);
old_wpa = fuse_find_writeback(fi, page->index, page->index);
if (!old_wpa) {
tree_insert(&fi->writepages, new_wpa);
@@ -1977,7 +1976,6 @@ static bool fuse_writepage_in_flight(struct
fuse_writepage_args *new_wpa,
return false;
}
- new_ap->num_pages = 1;
for (tmp = old_wpa->next; tmp; tmp = tmp->next) {
pgoff_t curr_index;
@@ -2020,7 +2018,7 @@ static int fuse_writepages_fill(struct page *page,
struct fuse_conn *fc = get_fuse_conn(inode);
struct page *tmp_page;
bool is_writeback;
- int err;
+ int index, err;
if (!data->ff) {
err = -EIO;
@@ -2083,44 +2081,48 @@ static int fuse_writepages_fill(struct page *page,
wpa->next = NULL;
ap->args.in_pages = true;
ap->args.end = fuse_writepage_end;
- ap->num_pages = 0;
+ ap->num_pages = 1;
wpa->inode = inode;
-
- spin_lock(&fi->lock);
- tree_insert(&fi->writepages, wpa);
- spin_unlock(&fi->lock);
-
+ index = 0;
data->wpa = wpa;
+ } else {
+ index = ap->num_pages;
}
set_page_writeback(page);
copy_highpage(tmp_page, page);
- ap->pages[ap->num_pages] = tmp_page;
- ap->descs[ap->num_pages].offset = 0;
- ap->descs[ap->num_pages].length = PAGE_SIZE;
+ ap->pages[index] = tmp_page;
+ ap->descs[index].offset = 0;
+ ap->descs[index].length = PAGE_SIZE;
inc_wb_stat(&inode_to_bdi(inode)->wb, WB_WRITEBACK);
inc_node_page_state(tmp_page, NR_WRITEBACK_TEMP);
err = 0;
- if (is_writeback && fuse_writepage_in_flight(wpa, page)) {
- end_page_writeback(page);
- data->wpa = NULL;
- goto out_unlock;
+ if (is_writeback) {
+ if (fuse_writepage_in_flight(wpa, page)) {
+ end_page_writeback(page);
+ data->wpa = NULL;
+ goto out_unlock;
+ }
+ } else if (!index) {
+ spin_lock(&fi->lock);
+ tree_insert(&fi->writepages, wpa);
+ spin_unlock(&fi->lock);
}
- data->orig_pages[ap->num_pages] = page;
-
- /*
- * Protected by fi->lock against concurrent access by
- * fuse_page_is_writeback().
- */
- spin_lock(&fi->lock);
- ap->num_pages++;
- spin_unlock(&fi->lock);
+ data->orig_pages[index] = page;
+ if (index) {
+ /*
+ * Protected by fi->lock against concurrent access by
+ * fuse_page_is_writeback().
+ */
+ spin_lock(&fi->lock);
+ ap->num_pages++;
+ spin_unlock(&fi->lock);
+ }
out_unlock:
unlock_page(page);
-
return err;
}
--
1.8.3.1
