fuse: pass iov[] to fuse_get_user_pages()

The patch makes preliminary work for the next patch optimizing scatter-gather
direct IO. The idea is to allow fuse_get_user_pages() to pack as many iov-s
to each fuse request as possible. So, here we only rework all related
call-paths to carry iov[] from fuse_direct_IO() to fuse_get_user_pages().

Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

1 files changed, 49 insertions, 54 deletions

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 3384a200b3ee..542ad97b103a 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1056,14 +1056,18 @@ static inline void fuse_page_descs_length_init(struct fuse_req *req)
                         req->page_descs[i].offset;
 }
 
-static int fuse_get_user_pages(struct fuse_req *req, const char __user *buf,
+static int fuse_get_user_pages(struct fuse_req *req, struct iov_iter *ii,
                                size_t *nbytesp, int write)
 {
         size_t nbytes = *nbytesp;
-        unsigned long user_addr = (unsigned long) buf;
-        unsigned offset = user_addr & ~PAGE_MASK;
+        size_t frag_size = min(iov_iter_single_seg_count(ii), nbytes);
+        unsigned long user_addr;
+        unsigned offset;
         int npages;
 
+        user_addr = (unsigned long)ii->iov->iov_base + ii->iov_offset;
+        offset = user_addr & ~PAGE_MASK;
+
         /* Special case for kernel I/O: can copy directly into the buffer */
         if (segment_eq(get_fs(), KERNEL_DS)) {
                 if (write)
@@ -1071,10 +1075,12 @@ static int fuse_get_user_pages(struct fuse_req *req, const char __user *buf,
                 else
                         req->out.args[0].value = (void *) user_addr;
 
+                iov_iter_advance(ii, frag_size);
+                *nbytesp = frag_size;
                 return 0;
         }
 
-        nbytes = min_t(size_t, nbytes, FUSE_MAX_PAGES_PER_REQ << PAGE_SHIFT);
+        nbytes = min_t(size_t, frag_size, FUSE_MAX_PAGES_PER_REQ << PAGE_SHIFT);
         npages = (nbytes + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
         npages = clamp(npages, 1, FUSE_MAX_PAGES_PER_REQ);
         npages = get_user_pages_fast(user_addr, npages, !write, req->pages);
@@ -1092,17 +1098,19 @@ static int fuse_get_user_pages(struct fuse_req *req, const char __user *buf,
 
         nbytes = (req->num_pages << PAGE_SHIFT) - req->page_descs[0].offset;
 
-        if (*nbytesp < nbytes)
+        if (frag_size < nbytes)
                 req->page_descs[req->num_pages - 1].length -=
-                        nbytes - *nbytesp;
+                        nbytes - frag_size;
 
-        *nbytesp = min(*nbytesp, nbytes);
+        *nbytesp = min(frag_size, nbytes);
+        iov_iter_advance(ii, *nbytesp);
 
         return 0;
 }
 
-ssize_t fuse_direct_io(struct file *file, const char __user *buf,
-                       size_t count, loff_t *ppos, int write)
+static ssize_t __fuse_direct_io(struct file *file, const struct iovec *iov,
+                                unsigned long nr_segs, size_t count,
+                                loff_t *ppos, int write)
 {
         struct fuse_file *ff = file->private_data;
         struct fuse_conn *fc = ff->fc;
@@ -1110,6 +1118,9 @@ ssize_t fuse_direct_io(struct file *file, const char __user *buf,
         loff_t pos = *ppos;
         ssize_t res = 0;
         struct fuse_req *req;
+        struct iov_iter ii;
+
+        iov_iter_init(&ii, iov, nr_segs, count, 0);
 
         req = fuse_get_req(fc, FUSE_MAX_PAGES_PER_REQ);
         if (IS_ERR(req))
@@ -1119,7 +1130,7 @@ ssize_t fuse_direct_io(struct file *file, const char __user *buf,
                 size_t nres;
                 fl_owner_t owner = current->files;
                 size_t nbytes = min(count, nmax);
-                int err = fuse_get_user_pages(req, buf, &nbytes, write);
+                int err = fuse_get_user_pages(req, &ii, &nbytes, write);
                 if (err) {
                         res = err;
                         break;
@@ -1142,7 +1153,6 @@ ssize_t fuse_direct_io(struct file *file, const char __user *buf,
                 count -= nres;
                 res += nres;
                 pos += nres;
-                buf += nres;
                 if (nres != nbytes)
                         break;
                 if (count) {
@@ -1159,10 +1169,17 @@ ssize_t fuse_direct_io(struct file *file, const char __user *buf,
 
         return res;
 }
+
+ssize_t fuse_direct_io(struct file *file, const char __user *buf,
+                       size_t count, loff_t *ppos, int write)
+{
+        struct iovec iov = { .iov_base = (void *)buf, .iov_len = count };
+        return __fuse_direct_io(file, &iov, 1, count, ppos, write);
+}
 EXPORT_SYMBOL_GPL(fuse_direct_io);
 
-static ssize_t fuse_direct_read(struct file *file, char __user *buf,
-                                     size_t count, loff_t *ppos)
+static ssize_t __fuse_direct_read(struct file *file, const struct iovec *iov,
+                                  unsigned long nr_segs, loff_t *ppos)
 {
         ssize_t res;
         struct inode *inode = file->f_path.dentry->d_inode;
@@ -1170,22 +1187,31 @@ static ssize_t fuse_direct_read(struct file *file, char __user *buf,
         if (is_bad_inode(inode))
                 return -EIO;
 
-        res = fuse_direct_io(file, buf, count, ppos, 0);
+        res = __fuse_direct_io(file, iov, nr_segs, iov_length(iov, nr_segs),
+                               ppos, 0);
 
         fuse_invalidate_attr(inode);
 
         return res;
 }
 
-static ssize_t __fuse_direct_write(struct file *file, const char __user *buf,
-                                   size_t count, loff_t *ppos)
+static ssize_t fuse_direct_read(struct file *file, char __user *buf,
+                                     size_t count, loff_t *ppos)
+{
+        struct iovec iov = { .iov_base = (void *)buf, .iov_len = count };
+        return __fuse_direct_read(file, &iov, 1, ppos);
+}
+
+static ssize_t __fuse_direct_write(struct file *file, const struct iovec *iov,
+                                   unsigned long nr_segs, loff_t *ppos)
 {
         struct inode *inode = file->f_path.dentry->d_inode;
+        size_t count = iov_length(iov, nr_segs);
         ssize_t res;
 
         res = generic_write_checks(file, ppos, &count, 0);
         if (!res) {
-                res = fuse_direct_io(file, buf, count, ppos, 1);
+                res = __fuse_direct_io(file, iov, nr_segs, count, ppos, 1);
                 if (res > 0)
                         fuse_write_update_size(inode, *ppos);
         }
@@ -1198,6 +1224,7 @@ static ssize_t __fuse_direct_write(struct file *file, const char __user *buf,
 static ssize_t fuse_direct_write(struct file *file, const char __user *buf,
                                  size_t count, loff_t *ppos)
 {
+        struct iovec iov = { .iov_base = (void *)buf, .iov_len = count };
         struct inode *inode = file->f_path.dentry->d_inode;
         ssize_t res;
 
@@ -1206,7 +1233,7 @@ static ssize_t fuse_direct_write(struct file *file, const char __user *buf,
 
         /* Don't allow parallel writes to the same file */
         mutex_lock(&inode->i_mutex);
-        res = __fuse_direct_write(file, buf, count, ppos);
+        res = __fuse_direct_write(file, &iov, 1, ppos);
         mutex_unlock(&inode->i_mutex);
 
         return res;
@@ -2167,41 +2194,6 @@ int fuse_notify_poll_wakeup(struct fuse_conn *fc,
         return 0;
 }
 
-static ssize_t fuse_loop_dio(struct file *filp, const struct iovec *iov,
-                             unsigned long nr_segs, loff_t *ppos, int rw)
-{
-        const struct iovec *vector = iov;
-        ssize_t ret = 0;
-
-        while (nr_segs > 0) {
-                void __user *base;
-                size_t len;
-                ssize_t nr;
-
-                base = vector->iov_base;
-                len = vector->iov_len;
-                vector++;
-                nr_segs--;
-
-                if (rw == WRITE)
-                        nr = __fuse_direct_write(filp, base, len, ppos);
-                else
-                        nr = fuse_direct_read(filp, base, len, ppos);
-
-                if (nr < 0) {
-                        if (!ret)
-                                ret = nr;
-                        break;
-                }
-                ret += nr;
-                if (nr != len)
-                        break;
-        }
-
-        return ret;
-}
-
-
 static ssize_t
 fuse_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
                         loff_t offset, unsigned long nr_segs)
@@ -2213,7 +2205,10 @@ fuse_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
         file = iocb->ki_filp;
         pos = offset;
 
-        ret = fuse_loop_dio(file, iov, nr_segs, &pos, rw);
+        if (rw == WRITE)
+                ret = __fuse_direct_write(file, iov, nr_segs, &pos);
+        else
+                ret = __fuse_direct_read(file, iov, nr_segs, &pos);
 
         return ret;
 }