sched: Remove proliferation of wait_on_bit() action functions

The current "wait_on_bit" interface requires an 'action'
function to be provided which does the actual waiting.
There are over 20 such functions, many of them identical.
Most cases can be satisfied by one of just two functions, one
which uses io_schedule() and one which just uses schedule().

So:
 Rename wait_on_bit and        wait_on_bit_lock to
        wait_on_bit_action and wait_on_bit_lock_action
 to make it explicit that they need an action function.

 Introduce new wait_on_bit{,_lock} and wait_on_bit{,_lock}_io
 which are *not* given an action function but implicitly use
 a standard one.
 The decision to error-out if a signal is pending is now made
 based on the 'mode' argument rather than being encoded in the action
 function.

 All instances of the old wait_on_bit and wait_on_bit_lock which
 can use the new version have been changed accordingly and their
 action functions have been discarded.
 wait_on_bit{_lock} does not return any specific error code in the
 event of a signal so the caller must check for non-zero and
 interpolate their own error code as appropriate.

The wait_on_bit() call in __fscache_wait_on_invalidate() was
ambiguous as it specified TASK_UNINTERRUPTIBLE but used
fscache_wait_bit_interruptible as an action function.
David Howells confirms this should be uniformly
"uninterruptible"

The main remaining user of wait_on_bit{,_lock}_action is NFS
which needs to use a freezer-aware schedule() call.

A comment in fs/gfs2/glock.c notes that having multiple 'action'
functions is useful as they display differently in the 'wchan'
field of 'ps'. (and /proc/$PID/wchan).
As the new bit_wait{,_io} functions are tagged "__sched", they
will not show up at all, but something higher in the stack.  So
the distinction will still be visible, only with different
function names (gds2_glock_wait versus gfs2_glock_dq_wait in the
gfs2/glock.c case).

Since first version of this patch (against 3.15) two new action
functions appeared, on in NFS and one in CIFS.  CIFS also now
uses an action function that makes the same freezer aware
schedule call as NFS.

Signed-off-by: NeilBrown <neilb@suse.de>
Acked-by: David Howells <dhowells@redhat.com> (fscache, keys)
Acked-by: Steven Whitehouse <swhiteho@redhat.com> (gfs2)
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steve French <sfrench@samba.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140707051603.28027.72349.stgit@notabene.brown
Signed-off-by: Ingo Molnar <mingo@kernel.org>

7 files changed, 13 insertions, 21 deletions

diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 4042ff58fe3f..524dd80d1898 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -361,8 +361,8 @@ start:
          * Prevent starvation issues if someone is doing a consistency
          * sync-to-disk
          */
-        ret = wait_on_bit(&NFS_I(mapping->host)->flags, NFS_INO_FLUSHING,
-                        nfs_wait_bit_killable, TASK_KILLABLE);
+        ret = wait_on_bit_action(&NFS_I(mapping->host)->flags, NFS_INO_FLUSHING,
+                                 nfs_wait_bit_killable, TASK_KILLABLE);
         if (ret)
                 return ret;
 
diff --git a/fs/nfs/filelayout/filelayoutdev.c b/fs/nfs/filelayout/filelayoutdev.c
index 44bf0140a4c7..e2a0361e24c6 100644
--- a/fs/nfs/filelayout/filelayoutdev.c
+++ b/fs/nfs/filelayout/filelayoutdev.c
@@ -783,8 +783,8 @@ nfs4_fl_select_ds_fh(struct pnfs_layout_segment *lseg, u32 j)
 static void nfs4_wait_ds_connect(struct nfs4_pnfs_ds *ds)
 {
         might_sleep();
-        wait_on_bit(&ds->ds_state, NFS4DS_CONNECTING,
-                        nfs_wait_bit_killable, TASK_KILLABLE);
+        wait_on_bit_action(&ds->ds_state, NFS4DS_CONNECTING,
+                           nfs_wait_bit_killable, TASK_KILLABLE);
 }
 
 static void nfs4_clear_ds_conn_bit(struct nfs4_pnfs_ds *ds)
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 9927913c97c2..b7b710e7d08e 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -1074,8 +1074,8 @@ int nfs_revalidate_mapping(struct inode *inode, struct address_space *mapping)
          * the bit lock here if it looks like we're going to be doing that.
          */
         for (;;) {
-                ret = wait_on_bit(bitlock, NFS_INO_INVALIDATING,
-                                  nfs_wait_bit_killable, TASK_KILLABLE);
+                ret = wait_on_bit_action(bitlock, NFS_INO_INVALIDATING,
+                                         nfs_wait_bit_killable, TASK_KILLABLE);
                 if (ret)
                         goto out;
                 spin_lock(&inode->i_lock);
diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index 848f6853c59e..42f121182167 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -1251,8 +1251,8 @@ int nfs4_wait_clnt_recover(struct nfs_client *clp)
         might_sleep();
 
         atomic_inc(&clp->cl_count);
-        res = wait_on_bit(&clp->cl_state, NFS4CLNT_MANAGER_RUNNING,
-                        nfs_wait_bit_killable, TASK_KILLABLE);
+        res = wait_on_bit_action(&clp->cl_state, NFS4CLNT_MANAGER_RUNNING,
+                                 nfs_wait_bit_killable, TASK_KILLABLE);
         if (res)
                 goto out;
         if (clp->cl_cons_state < 0)
diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index b6ee3a6ee96d..6104d3500b49 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -138,12 +138,6 @@ nfs_iocounter_wait(struct nfs_io_counter *c)
         return __nfs_iocounter_wait(c);
 }
 
-static int nfs_wait_bit_uninterruptible(void *word)
-{
-        io_schedule();
-        return 0;
-}
-
 /*
  * nfs_page_group_lock - lock the head of the page group
  * @req - request in group that is to be locked
@@ -158,7 +152,6 @@ nfs_page_group_lock(struct nfs_page *req)
         WARN_ON_ONCE(head != head->wb_head);
 
         wait_on_bit_lock(&head->wb_flags, PG_HEADLOCK,
-                        nfs_wait_bit_uninterruptible,
                         TASK_UNINTERRUPTIBLE);
 }
 
@@ -425,9 +418,8 @@ void nfs_release_request(struct nfs_page *req)
 int
 nfs_wait_on_request(struct nfs_page *req)
 {
-        return wait_on_bit(&req->wb_flags, PG_BUSY,
-                        nfs_wait_bit_uninterruptible,
-                        TASK_UNINTERRUPTIBLE);
+        return wait_on_bit_io(&req->wb_flags, PG_BUSY,
+                              TASK_UNINTERRUPTIBLE);
 }
 
 /*
diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 6fdcd233d6f7..a8914b335617 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -1885,7 +1885,7 @@ pnfs_layoutcommit_inode(struct inode *inode, bool sync)
         if (test_and_set_bit(NFS_INO_LAYOUTCOMMITTING, &nfsi->flags)) {
                 if (!sync)
                         goto out;
-                status = wait_on_bit_lock(&nfsi->flags,
+                status = wait_on_bit_lock_action(&nfsi->flags,
                                 NFS_INO_LAYOUTCOMMITTING,
                                 nfs_wait_bit_killable,
                                 TASK_KILLABLE);
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 98ff061ccaf3..f05f321f9d3d 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -397,7 +397,7 @@ int nfs_writepages(struct address_space *mapping, struct writeback_control *wbc)
         int err;
 
         /* Stop dirtying of new pages while we sync */
-        err = wait_on_bit_lock(bitlock, NFS_INO_FLUSHING,
+        err = wait_on_bit_lock_action(bitlock, NFS_INO_FLUSHING,
                         nfs_wait_bit_killable, TASK_KILLABLE);
         if (err)
                 goto out_err;
@@ -1475,7 +1475,7 @@ int nfs_commit_inode(struct inode *inode, int how)
                         return error;
                 if (!may_wait)
                         goto out_mark_dirty;
-                error = wait_on_bit(&NFS_I(inode)->flags,
+                error = wait_on_bit_action(&NFS_I(inode)->flags,
                                 NFS_INO_COMMIT,
                                 nfs_wait_bit_killable,
                                 TASK_KILLABLE);