LU-7981 llite: take trunc_sem only at vvp layer

The lli_trunc_sem is taken in 'read' mode in both
ll_page_mkwrite and vvp_io_fault_start. This can lead to a
deadlock with another thread which asks for the semaphore
in write mode between thse two read calls.

Since all users of lli_trunc_sem are in the vvp layer, we
can satisfy the requirement to exclude truncate by taking
the semaphore only in vvp_io_fault_start.

Signed-off-by: Patrick Farrell <paf@cray.com>
Change-Id: I7341d179f550835ccebfb1bb2d90260c1d5d0ff8
Reviewed-on: http://review.whamcloud.com/19315
Tested-by: Jenkins
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andriy Skulsyh
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>

diff --git a/lustre/llite/llite_mmap.c b/lustre/llite/llite_mmap.c
index 7d7177c..aea44c7 100644 (file)
--- a/lustre/llite/llite_mmap.c
+++ b/lustre/llite/llite_mmap.c
@@ -206,17 +206,11 @@ static int ll_page_mkwrite0(struct vm_area_struct *vma, struct page *vmpage,
 
        set = cfs_block_sigsinv(sigmask(SIGKILL) | sigmask(SIGTERM));
 
-       /* we grab lli_trunc_sem to exclude truncate case.
-        * Otherwise, we could add dirty pages into osc cache
-        * while truncate is on-going. */
        inode = vvp_object_inode(io->ci_obj);
        lli = ll_i2info(inode);
-       down_read(&lli->lli_trunc_sem);
 
        result = cl_io_loop(env, io);
 
-       up_read(&lli->lli_trunc_sem);
-
        cfs_restore_sigs(set);
 
         if (result == 0) {