From: Qu Wenruo <wqu@xxxxxxxx>
commit 2e3c25136adfb293d517e17f761d3b8a43a8fc22 upstream.
This function needs some extra checks on locked pages and eb. For error
handling we need to unlock locked pages and the eb.
There is a rare >0 return value branch, where all pages get locked
while write bio is not flushed.
Thankfully it's handled by the only caller, btree_write_cache_pages(),
as later write_one_eb() call will trigger submit_one_bio(). So there
shouldn't be any problem.
Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Ben Hutchings <ben.hutchings@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/btrfs/extent_io.c | 27 ++++++++++++++++++++++-----
1 file changed, 22 insertions(+), 5 deletions(-)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3554,19 +3554,27 @@ void wait_on_extent_buffer_writeback(str
TASK_UNINTERRUPTIBLE);
}
+/*
+ * Lock eb pages and flush the bio if we can't the locks
+ *
+ * Return 0 if nothing went wrong
+ * Return >0 is same as 0, except bio is not submitted
+ * Return <0 if something went wrong, no page is locked
+ */
static noinline_for_stack int
lock_extent_buffer_for_io(struct extent_buffer *eb,
struct btrfs_fs_info *fs_info,
struct extent_page_data *epd)
{
- int i, num_pages;
+ int i, num_pages, failed_page_nr;
int flush = 0;
int ret = 0;
if (!btrfs_try_tree_write_lock(eb)) {
- flush = 1;
ret = flush_write_bio(epd);
- BUG_ON(ret < 0);
+ if (ret < 0)
+ return ret;
+ flush = 1;
btrfs_tree_lock(eb);
}
@@ -3576,7 +3584,8 @@ lock_extent_buffer_for_io(struct extent_
return 0;
if (!flush) {
ret = flush_write_bio(epd);
- BUG_ON(ret < 0);
+ if (ret < 0)
+ return ret;
flush = 1;
}
while (1) {
@@ -3618,7 +3627,10 @@ lock_extent_buffer_for_io(struct extent_
if (!trylock_page(p)) {
if (!flush) {
ret = flush_write_bio(epd);
- BUG_ON(ret < 0);
+ if (ret < 0) {
+ failed_page_nr = i;
+ goto err_unlock;
+ }
flush = 1;
}
lock_page(p);
@@ -3626,6 +3638,11 @@ lock_extent_buffer_for_io(struct extent_
}
return ret;
+err_unlock:
+ /* Unlock already locked pages */
+ for (i = 0; i < failed_page_nr; i++)
+ unlock_page(eb->pages[i]);
+ return ret;
}
static void end_extent_buffer_writeback(struct extent_buffer *eb)
