btrfs: pass a valid extent map cache pointer to __get_extent_map()

We can pass a valid em cache pointer down to __get_extent_map() and
drop the validity check. This avoids the special case, the call stacks
are simple:

btrfs_read_folio
  btrfs_do_readpage
    __get_extent_map

extent_readahead
  contiguous_readpages
    btrfs_do_readpage
      __get_extent_map

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 6eebfe9d9a650a6c1bd56bdab2490e420de88d65..e73bffcaf763ba2c44f6641dd5d58f87f46c0608 100644 (file)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -970,7 +970,9 @@ static struct extent_map *__get_extent_map(struct inode *inode, struct page *pag
 {
        struct extent_map *em;
 
-       if (em_cached && *em_cached) {
+       ASSERT(em_cached);
+
+       if (*em_cached) {
                em = *em_cached;
                if (extent_map_in_tree(em) && start >= em->start &&
                    start < extent_map_end(em)) {
@@ -983,7 +985,7 @@ static struct extent_map *__get_extent_map(struct inode *inode, struct page *pag
        }
 
        em = btrfs_get_extent(BTRFS_I(inode), page, start, len);
-       if (em_cached && !IS_ERR(em)) {
+       if (!IS_ERR(em)) {
                BUG_ON(*em_cached);
                refcount_inc(&em->refs);
                *em_cached = em;
@@ -1154,11 +1156,14 @@ int btrfs_read_folio(struct file *file, struct folio *folio)
        u64 start = page_offset(page);
        u64 end = start + PAGE_SIZE - 1;
        struct btrfs_bio_ctrl bio_ctrl = { .opf = REQ_OP_READ };
+       struct extent_map *em_cached = NULL;
        int ret;
 
        btrfs_lock_and_flush_ordered_range(inode, start, end, NULL);
 
-       ret = btrfs_do_readpage(page, NULL, &bio_ctrl, NULL);
+       ret = btrfs_do_readpage(page, &em_cached, &bio_ctrl, NULL);
+       free_extent_map(em_cached);
+
        /*
         * If btrfs_do_readpage() failed we will want to submit the assembled
         * bio to do the cleanup.
@@ -1176,6 +1181,8 @@ static inline void contiguous_readpages(struct page *pages[], int nr_pages,
        struct btrfs_inode *inode = page_to_inode(pages[0]);
        int index;
 
+       ASSERT(em_cached);
+
        btrfs_lock_and_flush_ordered_range(inode, start, end, NULL);
 
        for (index = 0; index < nr_pages; index++) {