new helper: iov_iter_get_pages_alloc()

same as iov_iter_get_pages(), except that pages array is allocated
(kmalloc if possible, vmalloc if that fails) and left for caller to
free.  Lustre and NFS ->direct_IO() switched to it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

4 files changed, 167 insertions, 257 deletions

diff --git a/drivers/staging/lustre/lustre/llite/rw26.c b/drivers/staging/lustre/lustre/llite/rw26.c
index f718585c9e08..6b5994577b6b 100644
--- a/drivers/staging/lustre/lustre/llite/rw26.c
+++ b/drivers/staging/lustre/lustre/llite/rw26.c
@@ -218,14 +218,11 @@ static void ll_free_user_pages(struct page **pages, int npages, int do_dirty)
         int i;
 
         for (i = 0; i < npages; i++) {
-                if (pages[i] == NULL)
-                        break;
                 if (do_dirty)
                         set_page_dirty_lock(pages[i]);
                 page_cache_release(pages[i]);
         }
-
-        OBD_FREE_LARGE(pages, npages * sizeof(*pages));
+        kvfree(pages);
 }
 
 ssize_t ll_direct_rw_pages(const struct lu_env *env, struct cl_io *io,
@@ -370,10 +367,9 @@ static ssize_t ll_direct_IO_26(int rw, struct kiocb *iocb,
         struct file *file = iocb->ki_filp;
         struct inode *inode = file->f_mapping->host;
         struct ccc_object *obj = cl_inode2ccc(inode);
-        long count = iov_iter_count(iter);
-        long tot_bytes = 0, result = 0;
+        ssize_t count = iov_iter_count(iter);
+        ssize_t tot_bytes = 0, result = 0;
         struct ll_inode_info *lli = ll_i2info(inode);
-        unsigned long seg = 0;
         long size = MAX_DIO_SIZE;
         int refcheck;
 
@@ -407,63 +403,49 @@ static ssize_t ll_direct_IO_26(int rw, struct kiocb *iocb,
                 mutex_lock(&inode->i_mutex);
 
         LASSERT(obj->cob_transient_pages == 0);
-        for (seg = 0; seg < iter->nr_segs; seg++) {
-                long iov_left = iter->iov[seg].iov_len;
-                unsigned long user_addr = (unsigned long)iter->iov[seg].iov_base;
+        while (iov_iter_count(iter)) {
+                struct page **pages;
+                size_t offs;
 
+                count = min_t(size_t, iov_iter_count(iter), size);
                 if (rw == READ) {
                         if (file_offset >= i_size_read(inode))
                                 break;
-                        if (file_offset + iov_left > i_size_read(inode))
-                                iov_left = i_size_read(inode) - file_offset;
+                        if (file_offset + count > i_size_read(inode))
+                                count = i_size_read(inode) - file_offset;
                 }
 
-                while (iov_left > 0) {
-                        struct page **pages;
-                        int page_count, max_pages = 0;
-                        long bytes;
-
-                        bytes = min(size, iov_left);
-                        page_count = ll_get_user_pages(rw, user_addr, bytes,
-                                                       &pages, &max_pages);
-                        if (likely(page_count > 0)) {
-                                if (unlikely(page_count <  max_pages))
-                                        bytes = page_count << PAGE_CACHE_SHIFT;
-                                result = ll_direct_IO_26_seg(env, io, rw, inode,
-                                                             file->f_mapping,
-                                                             bytes, file_offset,
-                                                             pages, page_count);
-                                ll_free_user_pages(pages, max_pages, rw==READ);
-                        } else if (page_count == 0) {
-                                GOTO(out, result = -EFAULT);
-                        } else {
-                                result = page_count;
-                        }
-                        if (unlikely(result <= 0)) {
-                                /* If we can't allocate a large enough buffer
-                                 * for the request, shrink it to a smaller
-                                 * PAGE_SIZE multiple and try again.
-                                 * We should always be able to kmalloc for a
-                                 * page worth of page pointers = 4MB on i386. */
-                                if (result == -ENOMEM &&
-                                    size > (PAGE_CACHE_SIZE / sizeof(*pages)) *
-                                           PAGE_CACHE_SIZE) {
-                                        size = ((((size / 2) - 1) |
-                                                 ~CFS_PAGE_MASK) + 1) &
-                                                CFS_PAGE_MASK;
-                                        CDEBUG(D_VFSTRACE,"DIO size now %lu\n",
-                                               size);
-                                        continue;
-                                }
-
-                                GOTO(out, result);
+                result = iov_iter_get_pages_alloc(iter, &pages, count, &offs);
+                if (likely(result > 0)) {
+                        int n = (result + offs + PAGE_SIZE - 1) / PAGE_SIZE;
+                        result = ll_direct_IO_26_seg(env, io, rw, inode,
+                                                     file->f_mapping,
+                                                     result, file_offset,
+                                                     pages, n);
+                        ll_free_user_pages(pages, n, rw==READ);
+                }
+                if (unlikely(result <= 0)) {
+                        /* If we can't allocate a large enough buffer
+                         * for the request, shrink it to a smaller
+                         * PAGE_SIZE multiple and try again.
+                         * We should always be able to kmalloc for a
+                         * page worth of page pointers = 4MB on i386. */
+                        if (result == -ENOMEM &&
+                            size > (PAGE_CACHE_SIZE / sizeof(*pages)) *
+                                   PAGE_CACHE_SIZE) {
+                                size = ((((size / 2) - 1) |
+                                         ~CFS_PAGE_MASK) + 1) &
+                                        CFS_PAGE_MASK;
+                                CDEBUG(D_VFSTRACE,"DIO size now %lu\n",
+                                       size);
+                                continue;
                         }
 
-                        tot_bytes += result;
-                        file_offset += result;
-                        iov_left -= result;
-                        user_addr += result;
+                        GOTO(out, result);
                 }
+                iov_iter_advance(iter, result);
+                tot_bytes += result;
+                file_offset += result;
         }
 out:
         LASSERT(obj->cob_transient_pages == 0);
diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index 1d34f454989e..b122fe21fea0 100644
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -322,60 +322,37 @@ static const struct nfs_pgio_completion_ops nfs_direct_read_completion_ops = {
  * 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_segment(struct nfs_pageio_descriptor *desc,
-                                                const struct iovec *iov,
-                                                loff_t pos, bool uio)
-{
-        struct nfs_direct_req *dreq = desc->pg_dreq;
-        struct nfs_open_context *ctx = dreq->ctx;
-        struct inode *inode = ctx->dentry->d_inode;
-        unsigned long user_addr = (unsigned long)iov->iov_base;
-        size_t count = iov->iov_len;
-        size_t rsize = NFS_SERVER(inode)->rsize;
-        unsigned int pgbase;
-        int result;
-        ssize_t started = 0;
-        struct page **pagevec = NULL;
-        unsigned int npages;
-
-        do {
-                size_t bytes;
-                int i;
 
-                pgbase = user_addr & ~PAGE_MASK;
-                bytes = min(max_t(size_t, rsize, PAGE_SIZE), count);
+static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq,
+                                              struct iov_iter *iter,
+                                              loff_t pos)
+{
+        struct nfs_pageio_descriptor desc;
+        struct inode *inode = dreq->inode;
+        ssize_t result = -EINVAL;
+        size_t requested_bytes = 0;
+        size_t rsize = max_t(size_t, NFS_SERVER(inode)->rsize, PAGE_SIZE);
 
-                result = -ENOMEM;
-                npages = nfs_page_array_len(pgbase, bytes);
-                if (!pagevec)
-                        pagevec = kmalloc(npages * sizeof(struct page *),
-                                          GFP_KERNEL);
-                if (!pagevec)
-                        break;
-                if (uio) {
-                        down_read(&current->mm->mmap_sem);
-                        result = get_user_pages(current, current->mm, user_addr,
-                                        npages, 1, 0, pagevec, NULL);
-                        up_read(&current->mm->mmap_sem);
-                        if (result < 0)
-                                break;
-                } else {
-                        WARN_ON(npages != 1);
-                        result = get_kernel_page(user_addr, 1, pagevec);
-                        if (WARN_ON(result != 1))
-                                break;
-                }
+        NFS_PROTO(dreq->inode)->read_pageio_init(&desc, dreq->inode,
+                             &nfs_direct_read_completion_ops);
+        get_dreq(dreq);
+        desc.pg_dreq = dreq;
+        atomic_inc(&inode->i_dio_count);
 
-                if ((unsigned)result < npages) {
-                        bytes = result * PAGE_SIZE;
-                        if (bytes <= pgbase) {
-                                nfs_direct_release_pages(pagevec, result);
-                                break;
-                        }
-                        bytes -= pgbase;
-                        npages = result;
-                }
+        while (iov_iter_count(iter)) {
+                struct page **pagevec;
+                size_t bytes;
+                size_t pgbase;
+                unsigned npages, i;
 
+                result = iov_iter_get_pages_alloc(iter, &pagevec, 
+                                                  rsize, &pgbase);
+                if (result < 0)
+                        break;
+        
+                bytes = result;
+                iov_iter_advance(iter, bytes);
+                npages = (result + pgbase + PAGE_SIZE - 1) / PAGE_SIZE;
                 for (i = 0; i < npages; i++) {
                         struct nfs_page *req;
                         unsigned int req_len = min_t(size_t, bytes, PAGE_SIZE - pgbase);
@@ -389,55 +366,21 @@ static ssize_t nfs_direct_read_schedule_segment(struct nfs_pageio_descriptor *de
                         }
                         req->wb_index = pos >> PAGE_SHIFT;
                         req->wb_offset = pos & ~PAGE_MASK;
-                        if (!nfs_pageio_add_request(desc, req)) {
-                                result = desc->pg_error;
+                        if (!nfs_pageio_add_request(&desc, req)) {
+                                result = desc.pg_error;
                                 nfs_release_request(req);
                                 break;
                         }
                         pgbase = 0;
                         bytes -= req_len;
-                        started += req_len;
-                        user_addr += req_len;
+                        requested_bytes += req_len;
                         pos += req_len;
-                        count -= req_len;
                         dreq->bytes_left -= req_len;
                 }
-                /* The nfs_page now hold references to these pages */
                 nfs_direct_release_pages(pagevec, npages);
-        } while (count != 0 && result >= 0);
-
-        kfree(pagevec);
-
-        if (started)
-                return started;
-        return result < 0 ? (ssize_t) result : -EFAULT;
-}
-
-static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq,
-                                              struct iov_iter *iter,
-                                              loff_t pos, bool uio)
-{
-        struct nfs_pageio_descriptor desc;
-        struct inode *inode = dreq->inode;
-        ssize_t result = -EINVAL;
-        size_t requested_bytes = 0;
-        unsigned long seg;
-
-        NFS_PROTO(dreq->inode)->read_pageio_init(&desc, dreq->inode,
-                             &nfs_direct_read_completion_ops);
-        get_dreq(dreq);
-        desc.pg_dreq = dreq;
-        atomic_inc(&inode->i_dio_count);
-
-        for (seg = 0; seg < iter->nr_segs; seg++) {
-                const struct iovec *vec = &iter->iov[seg];
-                result = nfs_direct_read_schedule_segment(&desc, vec, pos, uio);
+                kvfree(pagevec);
                 if (result < 0)
                         break;
-                requested_bytes += result;
-                if ((size_t)result < vec->iov_len)
-                        break;
-                pos += vec->iov_len;
         }
 
         nfs_pageio_complete(&desc);
@@ -521,7 +464,7 @@ ssize_t nfs_file_direct_read(struct kiocb *iocb, struct iov_iter *iter,
                 dreq->iocb = iocb;
 
         NFS_I(inode)->read_io += count;
-        result = nfs_direct_read_schedule_iovec(dreq, iter, pos, uio);
+        result = nfs_direct_read_schedule_iovec(dreq, iter, pos);
 
         mutex_unlock(&inode->i_mutex);
 
@@ -677,109 +620,6 @@ static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode
 }
 #endif
 
-/*
- * NB: Return the value of the first error return code.  Subsequent
- *     errors after the first one are ignored.
- */
-/*
- * 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_segment(struct nfs_pageio_descriptor *desc,
-                                                 const struct iovec *iov,
-                                                 loff_t pos, bool uio)
-{
-        struct nfs_direct_req *dreq = desc->pg_dreq;
-        struct nfs_open_context *ctx = dreq->ctx;
-        struct inode *inode = ctx->dentry->d_inode;
-        unsigned long user_addr = (unsigned long)iov->iov_base;
-        size_t count = iov->iov_len;
-        size_t wsize = NFS_SERVER(inode)->wsize;
-        unsigned int pgbase;
-        int result;
-        ssize_t started = 0;
-        struct page **pagevec = NULL;
-        unsigned int npages;
-
-        do {
-                size_t bytes;
-                int i;
-
-                pgbase = user_addr & ~PAGE_MASK;
-                bytes = min(max_t(size_t, wsize, PAGE_SIZE), count);
-
-                result = -ENOMEM;
-                npages = nfs_page_array_len(pgbase, bytes);
-                if (!pagevec)
-                        pagevec = kmalloc(npages * sizeof(struct page *), GFP_KERNEL);
-                if (!pagevec)
-                        break;
-
-                if (uio) {
-                        down_read(&current->mm->mmap_sem);
-                        result = get_user_pages(current, current->mm, user_addr,
-                                                npages, 0, 0, pagevec, NULL);
-                        up_read(&current->mm->mmap_sem);
-                        if (result < 0)
-                                break;
-                } else {
-                        WARN_ON(npages != 1);
-                        result = get_kernel_page(user_addr, 0, pagevec);
-                        if (WARN_ON(result != 1))
-                                break;
-                }
-
-                if ((unsigned)result < npages) {
-                        bytes = result * PAGE_SIZE;
-                        if (bytes <= pgbase) {
-                                nfs_direct_release_pages(pagevec, result);
-                                break;
-                        }
-                        bytes -= pgbase;
-                        npages = result;
-                }
-
-                for (i = 0; i < npages; i++) {
-                        struct nfs_page *req;
-                        unsigned int req_len = min_t(size_t, bytes, PAGE_SIZE - pgbase);
-
-                        req = nfs_create_request(dreq->ctx, dreq->inode,
-                                                 pagevec[i],
-                                                 pgbase, req_len);
-                        if (IS_ERR(req)) {
-                                result = PTR_ERR(req);
-                                break;
-                        }
-                        nfs_lock_request(req);
-                        req->wb_index = pos >> PAGE_SHIFT;
-                        req->wb_offset = pos & ~PAGE_MASK;
-                        if (!nfs_pageio_add_request(desc, req)) {
-                                result = desc->pg_error;
-                                nfs_unlock_and_release_request(req);
-                                break;
-                        }
-                        pgbase = 0;
-                        bytes -= req_len;
-                        started += req_len;
-                        user_addr += req_len;
-                        pos += req_len;
-                        count -= req_len;
-                        dreq->bytes_left -= req_len;
-                }
-                /* The nfs_page now hold references to these pages */
-                nfs_direct_release_pages(pagevec, npages);
-        } while (count != 0 && result >= 0);
-
-        kfree(pagevec);
-
-        if (started)
-                return started;
-        return result < 0 ? (ssize_t) result : -EFAULT;
-}
-
 static void nfs_direct_write_completion(struct nfs_pgio_header *hdr)
 {
         struct nfs_direct_req *dreq = hdr->dreq;
@@ -859,15 +699,27 @@ static const struct nfs_pgio_completion_ops nfs_direct_write_completion_ops = {
         .completion = nfs_direct_write_completion,
 };
 
+
+/*
+ * NB: Return the value of the first error return code.  Subsequent
+ *     errors after the first one are ignored.
+ */
+/*
+ * 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_iovec(struct nfs_direct_req *dreq,
                                                struct iov_iter *iter,
-                                               loff_t pos, bool uio)
+                                               loff_t pos)
 {
         struct nfs_pageio_descriptor desc;
         struct inode *inode = dreq->inode;
         ssize_t result = 0;
         size_t requested_bytes = 0;
-        unsigned long seg;
+        size_t wsize = max_t(size_t, NFS_SERVER(inode)->wsize, PAGE_SIZE);
 
         NFS_PROTO(inode)->write_pageio_init(&desc, inode, FLUSH_COND_STABLE,
                               &nfs_direct_write_completion_ops);
@@ -875,16 +727,50 @@ static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq,
         get_dreq(dreq);
         atomic_inc(&inode->i_dio_count);
 
-        NFS_I(dreq->inode)->write_io += iov_iter_count(iter);
-        for (seg = 0; seg < iter->nr_segs; seg++) {
-                const struct iovec *vec = &iter->iov[seg];
-                result = nfs_direct_write_schedule_segment(&desc, vec, pos, uio);
+        NFS_I(inode)->write_io += iov_iter_count(iter);
+        while (iov_iter_count(iter)) {
+                struct page **pagevec;
+                size_t bytes;
+                size_t pgbase;
+                unsigned npages, i;
+
+                result = iov_iter_get_pages_alloc(iter, &pagevec, 
+                                                  wsize, &pgbase);
                 if (result < 0)
                         break;
-                requested_bytes += result;
-                if ((size_t)result < vec->iov_len)
+
+                bytes = result;
+                iov_iter_advance(iter, bytes);
+                npages = (result + pgbase + PAGE_SIZE - 1) / PAGE_SIZE;
+                for (i = 0; i < npages; i++) {
+                        struct nfs_page *req;
+                        unsigned int req_len = min_t(size_t, bytes, PAGE_SIZE - pgbase);
+
+                        req = nfs_create_request(dreq->ctx, inode,
+                                                 pagevec[i],
+                                                 pgbase, req_len);
+                        if (IS_ERR(req)) {
+                                result = PTR_ERR(req);
+                                break;
+                        }
+                        nfs_lock_request(req);
+                        req->wb_index = pos >> PAGE_SHIFT;
+                        req->wb_offset = pos & ~PAGE_MASK;
+                        if (!nfs_pageio_add_request(&desc, req)) {
+                                result = desc.pg_error;
+                                nfs_unlock_and_release_request(req);
+                                break;
+                        }
+                        pgbase = 0;
+                        bytes -= req_len;
+                        requested_bytes += req_len;
+                        pos += req_len;
+                        dreq->bytes_left -= req_len;
+                }
+                nfs_direct_release_pages(pagevec, npages);
+                kvfree(pagevec);
+                if (result < 0)
                         break;
-                pos += vec->iov_len;
         }
         nfs_pageio_complete(&desc);
 
@@ -985,7 +871,7 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter,
         if (!is_sync_kiocb(iocb))
                 dreq->iocb = iocb;
 
-        result = nfs_direct_write_schedule_iovec(dreq, iter, pos, uio);
+        result = nfs_direct_write_schedule_iovec(dreq, iter, pos);
 
         if (mapping->nrpages) {
                 invalidate_inode_pages2_range(mapping,
diff --git a/include/linux/uio.h b/include/linux/uio.h
index 2f8825b06680..4876e9f2a58f 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -73,6 +73,8 @@ void iov_iter_init(struct iov_iter *i, int direction, const struct iovec *iov,
                         unsigned long nr_segs, size_t count);
 ssize_t iov_iter_get_pages(struct iov_iter *i, struct page **pages,
                         size_t maxsize, size_t *start);
+ssize_t iov_iter_get_pages_alloc(struct iov_iter *i, struct page ***pages,
+                        size_t maxsize, size_t *start);
 int iov_iter_npages(const struct iov_iter *i, int maxpages);
 
 static inline size_t iov_iter_count(struct iov_iter *i)
diff --git a/mm/iov_iter.c b/mm/iov_iter.c
index 0b677f8f9bad..a5c691c1a283 100644
--- a/mm/iov_iter.c
+++ b/mm/iov_iter.c
@@ -1,6 +1,8 @@
 #include <linux/export.h>
 #include <linux/uio.h>
 #include <linux/pagemap.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
 
 size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
                          struct iov_iter *i)
@@ -263,6 +265,44 @@ ssize_t iov_iter_get_pages(struct iov_iter *i,
 }
 EXPORT_SYMBOL(iov_iter_get_pages);
 
+ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
+                   struct page ***pages, size_t maxsize,
+                   size_t *start)
+{
+        size_t offset = i->iov_offset;
+        const struct iovec *iov = i->iov;
+        size_t len;
+        unsigned long addr;
+        void *p;
+        int n;
+        int res;
+
+        len = iov->iov_len - offset;
+        if (len > i->count)
+                len = i->count;
+        if (len > maxsize)
+                len = maxsize;
+        addr = (unsigned long)iov->iov_base + offset;
+        len += *start = addr & (PAGE_SIZE - 1);
+        addr &= ~(PAGE_SIZE - 1);
+        n = (len + PAGE_SIZE - 1) / PAGE_SIZE;
+        
+        p = kmalloc(n * sizeof(struct page *), GFP_KERNEL);
+        if (!p)
+                p = vmalloc(n * sizeof(struct page *));
+        if (!p)
+                return -ENOMEM;
+
+        res = get_user_pages_fast(addr, n, (i->type & WRITE) != WRITE, p);
+        if (unlikely(res < 0)) {
+                kvfree(p);
+                return res;
+        }
+        *pages = p;
+        return (res == n ? len : res * PAGE_SIZE) - *start;
+}
+EXPORT_SYMBOL(iov_iter_get_pages_alloc);
+
 int iov_iter_npages(const struct iov_iter *i, int maxpages)
 {
         size_t offset = i->iov_offset;