Add a lock that will be needed by the next patch.
I am submitting this as a separate patch, because the act of adding an
extra field to "struct block_device" affects performance significantly.
So that performance change from adding the lock field can be
differentiated from the performance change of locking.
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
---
drivers/char/raw.c | 2 -
fs/block_dev.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++++--
include/linux/fs.h | 4 +++
3 files changed, 63 insertions(+), 3 deletions(-)
Index: linux-3.5-rc6-devel/include/linux/fs.h
===================================================================
--- linux-3.5-rc6-devel.orig/include/linux/fs.h 2012-07-16 20:20:12.000000000 +0200
+++ linux-3.5-rc6-devel/include/linux/fs.h 2012-07-16 01:29:21.000000000 +0200
@@ -713,6 +713,8 @@ struct block_device {
int bd_fsfreeze_count;
/* Mutex for freeze */
struct mutex bd_fsfreeze_mutex;
+ /* A semaphore that prevents I/O while block size is being changed */
+ struct rw_semaphore bd_block_size_semaphore;
};
/*
--
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