NFS: Use wait_on_atomic_t() for unlock after readahead

The use of wait_on_atomic_t() for waiting on I/O to complete before
unlocking allows us to git rid of the NFS_IO_INPROGRESS flag, and thus the
nfs_iocounter's flags member, and finally the nfs_iocounter altogether.
The count of I/O is moved to the lock context, and the counter
increment/decrement functions become simple enough to open-code.

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
[Trond: Fix up conflict with existing function nfs_wait_atomic_killable()]
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

6 files changed, 23 insertions, 70 deletions

diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 178ec8da028f..4ef8f5addcad 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -756,7 +756,7 @@ do_unlk(struct file *filp, int cmd, struct file_lock *fl, int is_local)
 
         l_ctx = nfs_get_lock_context(nfs_file_open_context(filp));
         if (!IS_ERR(l_ctx)) {
-                status = nfs_iocounter_wait(&l_ctx->io_count);
+                status = nfs_iocounter_wait(l_ctx);
                 nfs_put_lock_context(l_ctx);
                 if (status < 0)
                         return status;
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 74fb1223c2f5..4b63d1bd5820 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -71,19 +71,25 @@ nfs_fattr_to_ino_t(struct nfs_fattr *fattr)
         return nfs_fileid_to_ino_t(fattr->fileid);
 }
 
-/**
- * nfs_wait_bit_killable - helper for functions that are sleeping on bit locks
- * @word: long word containing the bit lock
- */
-int nfs_wait_bit_killable(struct wait_bit_key *key, int mode)
+static int nfs_wait_killable(int mode)
 {
         freezable_schedule_unsafe();
         if (signal_pending_state(mode, current))
                 return -ERESTARTSYS;
         return 0;
 }
+
+int nfs_wait_bit_killable(struct wait_bit_key *key, int mode)
+{
+        return nfs_wait_killable(mode);
+}
 EXPORT_SYMBOL_GPL(nfs_wait_bit_killable);
 
+int nfs_wait_atomic_killable(atomic_t *p)
+{
+        return nfs_wait_killable(TASK_KILLABLE);
+}
+
 /**
  * nfs_compat_user_ino64 - returns the user-visible inode number
  * @fileid: 64-bit fileid
@@ -699,7 +705,7 @@ static void nfs_init_lock_context(struct nfs_lock_context *l_ctx)
         l_ctx->lockowner.l_owner = current->files;
         l_ctx->lockowner.l_pid = current->tgid;
         INIT_LIST_HEAD(&l_ctx->list);
-        nfs_iocounter_init(&l_ctx->io_count);
+        atomic_set(&l_ctx->io_count, 0);
 }
 
 static struct nfs_lock_context *__nfs_find_lock_context(struct nfs_open_context *ctx)
diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index ee81792d2886..4e8cc942336c 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -238,7 +238,7 @@ extern void nfs_pgheader_init(struct nfs_pageio_descriptor *desc,
                               struct nfs_pgio_header *hdr,
                               void (*release)(struct nfs_pgio_header *hdr));
 void nfs_set_pgio_error(struct nfs_pgio_header *hdr, int error, loff_t pos);
-int nfs_iocounter_wait(struct nfs_io_counter *c);
+int nfs_iocounter_wait(struct nfs_lock_context *l_ctx);
 
 extern const struct nfs_pageio_ops nfs_pgio_rw_ops;
 struct nfs_pgio_header *nfs_pgio_header_alloc(const struct nfs_rw_ops *);
@@ -252,12 +252,6 @@ void nfs_free_request(struct nfs_page *req);
 struct nfs_pgio_mirror *
 nfs_pgio_current_mirror(struct nfs_pageio_descriptor *desc);
 
-static inline void nfs_iocounter_init(struct nfs_io_counter *c)
-{
-        c->flags = 0;
-        atomic_set(&c->io_count, 0);
-}
-
 static inline bool nfs_pgio_has_mirroring(struct nfs_pageio_descriptor *desc)
 {
         WARN_ON_ONCE(desc->pg_mirror_count < 1);
@@ -386,6 +380,7 @@ extern void nfs_clear_inode(struct inode *);
 extern void nfs_evict_inode(struct inode *);
 void nfs_zap_acl_cache(struct inode *inode);
 extern int nfs_wait_bit_killable(struct wait_bit_key *key, int mode);
+extern int nfs_wait_atomic_killable(atomic_t *p);
 
 /* super.c */
 extern const struct super_operations nfs_sops;
diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index eeddbf0bf4c4..cb7e73ba059c 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -101,53 +101,18 @@ nfs_page_free(struct nfs_page *p)
         kmem_cache_free(nfs_page_cachep, p);
 }
 
-static void
-nfs_iocounter_inc(struct nfs_io_counter *c)
-{
-        atomic_inc(&c->io_count);
-}
-
-static void
-nfs_iocounter_dec(struct nfs_io_counter *c)
-{
-        if (atomic_dec_and_test(&c->io_count)) {
-                clear_bit(NFS_IO_INPROGRESS, &c->flags);
-                smp_mb__after_atomic();
-                wake_up_bit(&c->flags, NFS_IO_INPROGRESS);
-        }
-}
-
-static int
-__nfs_iocounter_wait(struct nfs_io_counter *c)
-{
-        wait_queue_head_t *wq = bit_waitqueue(&c->flags, NFS_IO_INPROGRESS);
-        DEFINE_WAIT_BIT(q, &c->flags, NFS_IO_INPROGRESS);
-        int ret = 0;
-
-        do {
-                prepare_to_wait(wq, &q.wait, TASK_KILLABLE);
-                set_bit(NFS_IO_INPROGRESS, &c->flags);
-                if (atomic_read(&c->io_count) == 0)
-                        break;
-                ret = nfs_wait_bit_killable(&q.key, TASK_KILLABLE);
-        } while (atomic_read(&c->io_count) != 0 && !ret);
-        finish_wait(wq, &q.wait);
-        return ret;
-}
-
 /**
  * nfs_iocounter_wait - wait for i/o to complete
- * @c: nfs_io_counter to use
+ * @l_ctx: nfs_lock_context with io_counter to use
  *
  * returns -ERESTARTSYS if interrupted by a fatal signal.
  * Otherwise returns 0 once the io_count hits 0.
  */
 int
-nfs_iocounter_wait(struct nfs_io_counter *c)
+nfs_iocounter_wait(struct nfs_lock_context *l_ctx)
 {
-        if (atomic_read(&c->io_count) == 0)
-                return 0;
-        return __nfs_iocounter_wait(c);
+        return wait_on_atomic_t(&l_ctx->io_count, nfs_wait_atomic_killable,
+                        TASK_KILLABLE);
 }
 
 /*
@@ -370,7 +335,7 @@ nfs_create_request(struct nfs_open_context *ctx, struct page *page,
                 return ERR_CAST(l_ctx);
         }
         req->wb_lock_context = l_ctx;
-        nfs_iocounter_inc(&l_ctx->io_count);
+        atomic_inc(&l_ctx->io_count);
 
         /* Initialize the request struct. Initially, we assume a
          * long write-back delay. This will be adjusted in
@@ -431,7 +396,8 @@ static void nfs_clear_request(struct nfs_page *req)
                 req->wb_page = NULL;
         }
         if (l_ctx != NULL) {
-                nfs_iocounter_dec(&l_ctx->io_count);
+                if (atomic_dec_and_test(&l_ctx->io_count))
+                        wake_up_atomic_t(&l_ctx->io_count);
                 nfs_put_lock_context(l_ctx);
                 req->wb_lock_context = NULL;
         }
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 94828b3f8c95..8ba4f717b413 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -1565,14 +1565,6 @@ static void nfs_writeback_result(struct rpc_task *task,
         }
 }
 
-static int nfs_wait_atomic_killable(atomic_t *key)
-{
-        if (fatal_signal_pending(current))
-                return -ERESTARTSYS;
-        freezable_schedule_unsafe();
-        return 0;
-}
-
 static int wait_on_commit(struct nfs_mds_commit_info *cinfo)
 {
         return wait_on_atomic_t(&cinfo->rpcs_out,
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index 9eee972863a7..196aaceafda7 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -60,18 +60,12 @@ struct nfs_lockowner {
         pid_t l_pid;
 };
 
-#define NFS_IO_INPROGRESS 0
-struct nfs_io_counter {
-        unsigned long flags;
-        atomic_t io_count;
-};
-
 struct nfs_lock_context {
         atomic_t count;
         struct list_head list;
         struct nfs_open_context *open_context;
         struct nfs_lockowner lockowner;
-        struct nfs_io_counter io_count;
+        atomic_t io_count;
 };
 
 struct nfs4_state;