Discarding buffers uses a bunch of atomic operations when discarding buffers because ...... I can't think of a reason. Use a cmpxchg loop to clear all the necessary flags. In most (all?) cases this will be a single atomic operations.
Signed-off-by: Mel Gorman <[email protected]> --- fs/buffer.c | 14 +++++++++----- include/linux/buffer_head.h | 5 +++++ 2 files changed, 14 insertions(+), 5 deletions(-) diff --git a/fs/buffer.c b/fs/buffer.c index 9ddb9fc..e80012d 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -1485,14 +1485,18 @@ EXPORT_SYMBOL(set_bh_page); */ static void discard_buffer(struct buffer_head * bh) { + unsigned long b_state, b_state_old; + lock_buffer(bh); clear_buffer_dirty(bh); bh->b_bdev = NULL; - clear_buffer_mapped(bh); - clear_buffer_req(bh); - clear_buffer_new(bh); - clear_buffer_delay(bh); - clear_buffer_unwritten(bh); + b_state = bh->b_state; + for (;;) { + b_state_old = cmpxchg(&bh->b_state, b_state, (b_state & ~BUFFER_FLAGS_DISCARD)); + if (b_state_old == b_state) + break; + b_state = b_state_old; + } unlock_buffer(bh); } diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h index c40302f..95f565a 100644 --- a/include/linux/buffer_head.h +++ b/include/linux/buffer_head.h @@ -77,6 +77,11 @@ struct buffer_head { atomic_t b_count; /* users using this buffer_head */ }; +/* Bits that are cleared during an invalidate */ +#define BUFFER_FLAGS_DISCARD \ + (1 << BH_Mapped | 1 << BH_New | 1 << BH_Req | \ + 1 << BH_Delay | 1 << BH_Unwritten) + /* * macro tricks to expand the set_buffer_foo(), clear_buffer_foo() * and buffer_foo() functions. -- 1.8.4.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
