diff options
| -rw-r--r-- | fs/buffer.c | 15 |
1 files changed, 14 insertions, 1 deletions
diff --git a/fs/buffer.c b/fs/buffer.c index 98196327ddf0..39ff14403d13 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -1181,7 +1181,20 @@ __getblk_slow(struct block_device *bdev, sector_t block, int size) void mark_buffer_dirty(struct buffer_head *bh) { WARN_ON_ONCE(!buffer_uptodate(bh)); - if (!buffer_dirty(bh) && !test_set_buffer_dirty(bh)) + + /* + * Very *carefully* optimize the it-is-already-dirty case. + * + * Don't let the final "is it dirty" escape to before we + * perhaps modified the buffer. + */ + if (buffer_dirty(bh)) { + smp_mb(); + if (buffer_dirty(bh)) + return; + } + + if (!test_set_buffer_dirty(bh)) __set_page_dirty(bh->b_page, page_mapping(bh->b_page), 0); } |