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path: root/fs/btrfs/extent_io.c
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Diffstat (limited to 'fs/btrfs/extent_io.c')
-rw-r--r--fs/btrfs/extent_io.c13
1 files changed, 13 insertions, 0 deletions
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 7441245b1ceb..61594eaf1f89 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4333,6 +4333,19 @@ int read_extent_buffer_pages(struct extent_buffer *eb, int wait, int mirror_num,
if (test_and_set_bit(EXTENT_BUFFER_READING, &eb->bflags))
goto done;
+ /*
+ * Between the initial test_bit(EXTENT_BUFFER_UPTODATE) and the above
+ * test_and_set_bit(EXTENT_BUFFER_READING), someone else could have
+ * started and finished reading the same eb. In this case, UPTODATE
+ * will now be set, and we shouldn't read it in again.
+ */
+ if (unlikely(test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags))) {
+ clear_bit(EXTENT_BUFFER_READING, &eb->bflags);
+ smp_mb__after_atomic();
+ wake_up_bit(&eb->bflags, EXTENT_BUFFER_READING);
+ return 0;
+ }
+
clear_bit(EXTENT_BUFFER_READ_ERR, &eb->bflags);
eb->read_mirror = 0;
check_buffer_tree_ref(eb);