NFS: alloc nfs_read/write_data as direct I/O is scheduled

Re-arrange the logic in the NFS direct I/O path so that nfs_read/write_data
structs are allocated just before they are scheduled, rather than
allocating them all at once before we start scheduling requests.

Signed-off-by: Chuck Lever <cel@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 65 insertions, 145 deletions

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index b1630d53fbb1..e25b7595b7ad 100644
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -68,8 +68,6 @@ struct nfs_direct_req {
         struct kref             kref;           /* release manager */
 
         /* I/O parameters */
-        struct list_head        list,           /* nfs_read/write_data structs */
-                                rewrite_list;   /* saved nfs_write_data structs */
         struct nfs_open_context *ctx;           /* file open context info */
         struct kiocb *          iocb;           /* controlling i/o request */
         struct inode *          inode;          /* target file of i/o */
@@ -82,6 +80,7 @@ struct nfs_direct_req {
         struct completion       completion;     /* wait for i/o completion */
 
         /* commit state */
+        struct list_head        rewrite_list;   /* saved nfs_write_data structs */
         struct nfs_write_data * commit_data;    /* special write_data for commits */
         int                     flags;
 #define NFS_ODIRECT_DO_COMMIT           (1)     /* an unstable reply was received */
@@ -116,6 +115,11 @@ static inline int nfs_direct_count_pages(unsigned long user_addr, size_t size)
         return page_count;
 }
 
+static inline unsigned int nfs_max_pages(unsigned int size)
+{
+        return (size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
+}
+
 /**
  * nfs_direct_IO - NFS address space operation for direct I/O
  * @rw: direction (read or write)
@@ -164,8 +168,8 @@ static inline struct nfs_direct_req *nfs_direct_req_alloc(void)
                 return NULL;
 
         kref_init(&dreq->kref);
+        kref_get(&dreq->kref);
         init_completion(&dreq->completion);
-        INIT_LIST_HEAD(&dreq->list);
         INIT_LIST_HEAD(&dreq->rewrite_list);
         dreq->iocb = NULL;
         dreq->ctx = NULL;
@@ -228,49 +232,6 @@ static void nfs_direct_complete(struct nfs_direct_req *dreq)
 }
 
 /*
- * Note we also set the number of requests we have in the dreq when we are
- * done.  This prevents races with I/O completion so we will always wait
- * until all requests have been dispatched and completed.
- */
-static struct nfs_direct_req *nfs_direct_read_alloc(size_t nbytes, size_t rsize)
-{
-        struct list_head *list;
-        struct nfs_direct_req *dreq;
-        unsigned int rpages = (rsize + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
-
-        dreq = nfs_direct_req_alloc();
-        if (!dreq)
-                return NULL;
-
-        list = &dreq->list;
-        for(;;) {
-                struct nfs_read_data *data = nfs_readdata_alloc(rpages);
-
-                if (unlikely(!data)) {
-                        while (!list_empty(list)) {
-                                data = list_entry(list->next,
-                                                  struct nfs_read_data, pages);
-                                list_del(&data->pages);
-                                nfs_readdata_free(data);
-                        }
-                        kref_put(&dreq->kref, nfs_direct_req_release);
-                        return NULL;
-                }
-
-                INIT_LIST_HEAD(&data->pages);
-                list_add(&data->pages, list);
-
-                data->req = (struct nfs_page *) dreq;
-                get_dreq(dreq);
-                if (nbytes <= rsize)
-                        break;
-                nbytes -= rsize;
-        }
-        kref_get(&dreq->kref);
-        return dreq;
-}
-
-/*
  * We must hold a reference to all the pages in this direct read request
  * until the RPCs complete.  This could be long *after* we are woken up in
  * nfs_direct_wait (for instance, if someone hits ^C on a slow server).
@@ -305,42 +266,53 @@ static const struct rpc_call_ops nfs_read_direct_ops = {
 };
 
 /*
- * For each nfs_read_data struct that was allocated on the list, dispatch
- * an NFS READ operation.  If get_user_pages() fails, we stop sending reads.
- * Read length accounting is handled by nfs_direct_read_result().
- * Otherwise, if no requests have been sent, just return an error.
+ * For each rsize'd chunk of the user's buffer, dispatch an NFS READ
+ * operation.  If nfs_readdata_alloc() or get_user_pages() fails,
+ * bail and stop sending more reads.  Read length accounting is
+ * handled automatically by nfs_direct_read_result().  Otherwise, if
+ * no requests have been sent, just return an error.
  */
 static ssize_t nfs_direct_read_schedule(struct nfs_direct_req *dreq, unsigned long user_addr, size_t count, loff_t pos)
 {
         struct nfs_open_context *ctx = dreq->ctx;
         struct inode *inode = ctx->dentry->d_inode;
-        struct list_head *list = &dreq->list;
         size_t rsize = NFS_SERVER(inode)->rsize;
+        unsigned int rpages = nfs_max_pages(rsize);
         unsigned int pgbase;
         int result;
         ssize_t started = 0;
-        struct nfs_read_data *data;
+
+        get_dreq(dreq);
 
         pgbase = user_addr & ~PAGE_MASK;
         do {
+                struct nfs_read_data *data;
                 size_t bytes;
 
+                result = -ENOMEM;
+                data = nfs_readdata_alloc(rpages);
+                if (unlikely(!data))
+                        break;
+
                 bytes = rsize;
                 if (count < rsize)
                         bytes = count;
 
-                BUG_ON(list_empty(list));
-                data = list_entry(list->next, struct nfs_read_data, pages);
-                list_del_init(&data->pages);
-
                 data->npages = nfs_direct_count_pages(user_addr, bytes);
                 down_read(&current->mm->mmap_sem);
                 result = get_user_pages(current, current->mm, user_addr,
                                         data->npages, 1, 0, data->pagevec, NULL);
                 up_read(&current->mm->mmap_sem);
-                if (unlikely(result < data->npages))
-                        goto out_err;
+                if (unlikely(result < data->npages)) {
+                        if (result > 0)
+                                nfs_direct_release_pages(data->pagevec, result);
+                        nfs_readdata_release(data);
+                        break;
+                }
 
+                get_dreq(dreq);
+
+                data->req = (struct nfs_page *) dreq;
                 data->inode = inode;
                 data->cred = ctx->cred;
                 data->args.fh = NFS_FH(inode);
@@ -378,21 +350,9 @@ static ssize_t nfs_direct_read_schedule(struct nfs_direct_req *dreq, unsigned lo
 
                 count -= bytes;
         } while (count != 0);
-        BUG_ON(!list_empty(list));
-        return 0;
 
-out_err:
-        if (result > 0)
-                nfs_direct_release_pages(data->pagevec, result);
-
-        list_add(&data->pages, list);
-        while (!list_empty(list)) {
-                data = list_entry(list->next, struct nfs_read_data, pages);
-                list_del(&data->pages);
-                nfs_readdata_free(data);
-                if (put_dreq(dreq))
-                        nfs_direct_complete(dreq);
-        }
+        if (put_dreq(dreq))
+                nfs_direct_complete(dreq);
 
         if (started)
                 return 0;
@@ -401,13 +361,13 @@ out_err:
 
 static ssize_t nfs_direct_read(struct kiocb *iocb, unsigned long user_addr, size_t count, loff_t pos)
 {
-        ssize_t result;
+        ssize_t result = 0;
         sigset_t oldset;
         struct inode *inode = iocb->ki_filp->f_mapping->host;
         struct rpc_clnt *clnt = NFS_CLIENT(inode);
         struct nfs_direct_req *dreq;
 
-        dreq = nfs_direct_read_alloc(count, NFS_SERVER(inode)->rsize);
+        dreq = nfs_direct_req_alloc();
         if (!dreq)
                 return -ENOMEM;
 
@@ -428,9 +388,8 @@ static ssize_t nfs_direct_read(struct kiocb *iocb, unsigned long user_addr, size
 
 static void nfs_direct_free_writedata(struct nfs_direct_req *dreq)
 {
-        list_splice_init(&dreq->rewrite_list, &dreq->list);
-        while (!list_empty(&dreq->list)) {
-                struct nfs_write_data *data = list_entry(dreq->list.next, struct nfs_write_data, pages);
+        while (!list_empty(&dreq->rewrite_list)) {
+                struct nfs_write_data *data = list_entry(dreq->rewrite_list.next, struct nfs_write_data, pages);
                 list_del(&data->pages);
                 nfs_direct_release_pages(data->pagevec, data->npages);
                 nfs_writedata_release(data);
@@ -584,47 +543,6 @@ static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode
 }
 #endif
 
-static struct nfs_direct_req *nfs_direct_write_alloc(size_t nbytes, size_t wsize)
-{
-        struct list_head *list;
-        struct nfs_direct_req *dreq;
-        unsigned int wpages = (wsize + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
-
-        dreq = nfs_direct_req_alloc();
-        if (!dreq)
-                return NULL;
-
-        list = &dreq->list;
-        for(;;) {
-                struct nfs_write_data *data = nfs_writedata_alloc(wpages);
-
-                if (unlikely(!data)) {
-                        while (!list_empty(list)) {
-                                data = list_entry(list->next,
-                                                  struct nfs_write_data, pages);
-                                list_del(&data->pages);
-                                nfs_writedata_free(data);
-                        }
-                        kref_put(&dreq->kref, nfs_direct_req_release);
-                        return NULL;
-                }
-
-                INIT_LIST_HEAD(&data->pages);
-                list_add(&data->pages, list);
-
-                data->req = (struct nfs_page *) dreq;
-                get_dreq(dreq);
-                if (nbytes <= wsize)
-                        break;
-                nbytes -= wsize;
-        }
-
-        nfs_alloc_commit_data(dreq);
-
-        kref_get(&dreq->kref);
-        return dreq;
-}
-
 static void nfs_direct_write_result(struct rpc_task *task, void *calldata)
 {
         struct nfs_write_data *data = calldata;
@@ -677,43 +595,55 @@ static const struct rpc_call_ops nfs_write_direct_ops = {
 };
 
 /*
- * For each nfs_write_data struct that was allocated on the list, dispatch
- * an NFS WRITE operation.  If get_user_pages() fails, we stop sending writes.
- * Write length accounting is handled by nfs_direct_write_result().
- * Otherwise, if no requests have been sent, just return an error.
+ * For each wsize'd chunk of the user's buffer, dispatch an NFS WRITE
+ * operation.  If nfs_writedata_alloc() or get_user_pages() fails,
+ * bail and stop sending more writes.  Write length accounting is
+ * handled automatically by nfs_direct_write_result().  Otherwise, if
+ * no requests have been sent, just return an error.
  */
 static ssize_t nfs_direct_write_schedule(struct nfs_direct_req *dreq, unsigned long user_addr, size_t count, loff_t pos, int sync)
 {
         struct nfs_open_context *ctx = dreq->ctx;
         struct inode *inode = ctx->dentry->d_inode;
-        struct list_head *list = &dreq->list;
         size_t wsize = NFS_SERVER(inode)->wsize;
+        unsigned int wpages = nfs_max_pages(wsize);
         unsigned int pgbase;
         int result;
         ssize_t started = 0;
-        struct nfs_write_data *data;
+
+        get_dreq(dreq);
 
         pgbase = user_addr & ~PAGE_MASK;
         do {
+                struct nfs_write_data *data;
                 size_t bytes;
 
+                result = -ENOMEM;
+                data = nfs_writedata_alloc(wpages);
+                if (unlikely(!data))
+                        break;
+
                 bytes = wsize;
                 if (count < wsize)
                         bytes = count;
 
-                BUG_ON(list_empty(list));
-                data = list_entry(list->next, struct nfs_write_data, pages);
-
                 data->npages = nfs_direct_count_pages(user_addr, bytes);
                 down_read(&current->mm->mmap_sem);
                 result = get_user_pages(current, current->mm, user_addr,
                                         data->npages, 0, 0, data->pagevec, NULL);
                 up_read(&current->mm->mmap_sem);
-                if (unlikely(result < data->npages))
-                        goto out_err;
+                if (unlikely(result < data->npages)) {
+                        if (result > 0)
+                                nfs_direct_release_pages(data->pagevec, result);
+                        nfs_writedata_release(data);
+                        break;
+                }
+
+                get_dreq(dreq);
 
                 list_move_tail(&data->pages, &dreq->rewrite_list);
 
+                data->req = (struct nfs_page *) dreq;
                 data->inode = inode;
                 data->cred = ctx->cred;
                 data->args.fh = NFS_FH(inode);
@@ -752,21 +682,9 @@ static ssize_t nfs_direct_write_schedule(struct nfs_direct_req *dreq, unsigned l
 
                 count -= bytes;
         } while (count != 0);
-        BUG_ON(!list_empty(list));
-        return 0;
-
-out_err:
-        if (result > 0)
-                nfs_direct_release_pages(data->pagevec, result);
 
-        list_add(&data->pages, list);
-        while (!list_empty(list)) {
-                data = list_entry(list->next, struct nfs_write_data, pages);
-                list_del(&data->pages);
-                nfs_writedata_free(data);
-                if (put_dreq(dreq))
-                        nfs_direct_write_complete(dreq, inode);
-        }
+        if (put_dreq(dreq))
+                nfs_direct_write_complete(dreq, inode);
 
         if (started)
                 return 0;
@@ -775,7 +693,7 @@ out_err:
 
 static ssize_t nfs_direct_write(struct kiocb *iocb, unsigned long user_addr, size_t count, loff_t pos)
 {
-        ssize_t result;
+        ssize_t result = 0;
         sigset_t oldset;
         struct inode *inode = iocb->ki_filp->f_mapping->host;
         struct rpc_clnt *clnt = NFS_CLIENT(inode);
@@ -783,9 +701,11 @@ static ssize_t nfs_direct_write(struct kiocb *iocb, unsigned long user_addr, siz
         size_t wsize = NFS_SERVER(inode)->wsize;
         int sync = 0;
 
-        dreq = nfs_direct_write_alloc(count, wsize);
+        dreq = nfs_direct_req_alloc();
         if (!dreq)
                 return -ENOMEM;
+        nfs_alloc_commit_data(dreq);
+
         if (dreq->commit_data == NULL || count < wsize)
                 sync = FLUSH_STABLE;