btrfs: extent_io: Move the BUG_ON() in flush_write_bio() one level up

commit f4340622e02261fae599e3da936ff4808b418173 upstream.

We have a BUG_ON() in flush_write_bio() to handle the return value of
submit_one_bio().

Move the BUG_ON() one level up to all its callers.

This patch will introduce temporary variable, @flush_ret to keep code
change minimal in this patch. That variable will be cleaned up when
enhancing the error handling later.

Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
[bwh: Cherry-picked for 4.19 to ease backporting later fixes]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 128da03721d01819e90736c8a418d887771e03b1..e6dab32e37f45972d69a94539d995698b2581c3e 100644 (file)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -160,15 +160,28 @@ static int __must_check submit_one_bio(struct bio *bio, int mirror_num,
        return blk_status_to_errno(ret);
 }
 
-static void flush_write_bio(struct extent_page_data *epd)
+/*
+ * Submit bio from extent page data via submit_one_bio
+ *
+ * Return 0 if everything is OK.
+ * Return <0 for error.
+ */
+static int __must_check flush_write_bio(struct extent_page_data *epd)
 {
-       if (epd->bio) {
-               int ret;
+       int ret = 0;
 
+       if (epd->bio) {
                ret = submit_one_bio(epd->bio, 0, 0);
-               BUG_ON(ret < 0); /* -ENOMEM */
+               /*
+                * Clean up of epd->bio is handled by its endio function.
+                * And endio is either triggered by successful bio execution
+                * or the error handler of submit bio hook.
+                * So at this point, no matter what happened, we don't need
+                * to clean up epd->bio.
+                */
                epd->bio = NULL;
        }
+       return ret;
 }
 
 int __init extent_io_init(void)
@@ -3538,7 +3551,8 @@ lock_extent_buffer_for_io(struct extent_buffer *eb,
 
        if (!btrfs_try_tree_write_lock(eb)) {
                flush = 1;
-               flush_write_bio(epd);
+               ret = flush_write_bio(epd);
+               BUG_ON(ret < 0);
                btrfs_tree_lock(eb);
        }
 
@@ -3547,7 +3561,8 @@ lock_extent_buffer_for_io(struct extent_buffer *eb,
                if (!epd->sync_io)
                        return 0;
                if (!flush) {
-                       flush_write_bio(epd);
+                       ret = flush_write_bio(epd);
+                       BUG_ON(ret < 0);
                        flush = 1;
                }
                while (1) {
@@ -3588,7 +3603,8 @@ lock_extent_buffer_for_io(struct extent_buffer *eb,
 
                if (!trylock_page(p)) {
                        if (!flush) {
-                               flush_write_bio(epd);
+                               ret = flush_write_bio(epd);
+                               BUG_ON(ret < 0);
                                flush = 1;
                        }
                        lock_page(p);
@@ -3779,6 +3795,7 @@ int btree_write_cache_pages(struct address_space *mapping,
                .sync_io = wbc->sync_mode == WB_SYNC_ALL,
        };
        int ret = 0;
+       int flush_ret;
        int done = 0;
        int nr_to_write_done = 0;
        struct pagevec pvec;
@@ -3878,7 +3895,8 @@ retry:
                index = 0;
                goto retry;
        }
-       flush_write_bio(&epd);
+       flush_ret = flush_write_bio(&epd);
+       BUG_ON(flush_ret < 0);
        return ret;
 }
 
@@ -3975,7 +3993,8 @@ retry:
                         * tmpfs file mapping
                         */
                        if (!trylock_page(page)) {
-                               flush_write_bio(epd);
+                               ret = flush_write_bio(epd);
+                               BUG_ON(ret < 0);
                                lock_page(page);
                        }
 
@@ -3985,8 +4004,10 @@ retry:
                        }
 
                        if (wbc->sync_mode != WB_SYNC_NONE) {
-                               if (PageWriteback(page))
-                                       flush_write_bio(epd);
+                               if (PageWriteback(page)) {
+                                       ret = flush_write_bio(epd);
+                                       BUG_ON(ret < 0);
+                               }
                                wait_on_page_writeback(page);
                        }
 
@@ -4045,6 +4066,7 @@ retry:
 int extent_write_full_page(struct page *page, struct writeback_control *wbc)
 {
        int ret;
+       int flush_ret;
        struct extent_page_data epd = {
                .bio = NULL,
                .tree = &BTRFS_I(page->mapping->host)->io_tree,
@@ -4054,7 +4076,8 @@ int extent_write_full_page(struct page *page, struct writeback_control *wbc)
 
        ret = __extent_writepage(page, wbc, &epd);
 
-       flush_write_bio(&epd);
+       flush_ret = flush_write_bio(&epd);
+       BUG_ON(flush_ret < 0);
        return ret;
 }
 
@@ -4062,6 +4085,7 @@ int extent_write_locked_range(struct inode *inode, u64 start, u64 end,
                              int mode)
 {
        int ret = 0;
+       int flush_ret;
        struct address_space *mapping = inode->i_mapping;
        struct extent_io_tree *tree = &BTRFS_I(inode)->io_tree;
        struct page *page;
@@ -4096,7 +4120,8 @@ int extent_write_locked_range(struct inode *inode, u64 start, u64 end,
                start += PAGE_SIZE;
        }
 
-       flush_write_bio(&epd);
+       flush_ret = flush_write_bio(&epd);
+       BUG_ON(flush_ret < 0);
        return ret;
 }
 
@@ -4104,6 +4129,7 @@ int extent_writepages(struct address_space *mapping,
                      struct writeback_control *wbc)
 {
        int ret = 0;
+       int flush_ret;
        struct extent_page_data epd = {
                .bio = NULL,
                .tree = &BTRFS_I(mapping->host)->io_tree,
@@ -4112,7 +4138,8 @@ int extent_writepages(struct address_space *mapping,
        };
 
        ret = extent_write_cache_pages(mapping, wbc, &epd);
-       flush_write_bio(&epd);
+       flush_ret = flush_write_bio(&epd);
+       BUG_ON(flush_ret < 0);
        return ret;
 }