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 <[email protected]> --- 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; }; /* -- 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/
