fuse: make fuse_direct_io() aware about AIO

The patch implements passing "struct fuse_io_priv *io" down the stack up to
fuse_send_read/write where it is used to submit request asynchronously.
io->async==0 designates synchronous processing.

Non-trivial part of the patch is changes in fuse_direct_io(): resources
like fuse requests and user pages cannot be released immediately in async
case.

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

4 files changed, 58 insertions, 21 deletions

diff --git a/fs/fuse/cuse.c b/fs/fuse/cuse.c
index c59c097eb2e9..b3aaf7b3578b 100644
--- a/fs/fuse/cuse.c
+++ b/fs/fuse/cuse.c
@@ -92,8 +92,9 @@ static ssize_t cuse_read(struct file *file, char __user *buf, size_t count,
 {
         loff_t pos = 0;
         struct iovec iov = { .iov_base = buf, .iov_len = count };
+        struct fuse_io_priv io = { .async = 0, .file = file };
 
-        return fuse_direct_io(file, &iov, 1, count, &pos, 0);
+        return fuse_direct_io(&io, &iov, 1, count, &pos, 0);
 }
 
 static ssize_t cuse_write(struct file *file, const char __user *buf,
@@ -101,12 +102,13 @@ static ssize_t cuse_write(struct file *file, const char __user *buf,
 {
         loff_t pos = 0;
         struct iovec iov = { .iov_base = (void __user *)buf, .iov_len = count };
+        struct fuse_io_priv io = { .async = 0, .file = file };
 
         /*
          * No locking or generic_write_checks(), the server is
          * responsible for locking and sanity checks.
          */
-        return fuse_direct_io(file, &iov, 1, count, &pos, 1);
+        return fuse_direct_io(&io, &iov, 1, count, &pos, 1);
 }
 
 static int cuse_open(struct inode *inode, struct file *file)
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index be5c7e13320c..07bdb14ae7a3 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -111,7 +111,7 @@ static void restore_sigs(sigset_t *oldset)
         sigprocmask(SIG_SETMASK, oldset, NULL);
 }
 
-static void __fuse_get_request(struct fuse_req *req)
+void __fuse_get_request(struct fuse_req *req)
 {
         atomic_inc(&req->count);
 }
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 4002889fbcc1..e207dcdf32c0 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -593,14 +593,16 @@ static size_t fuse_async_req_send(struct fuse_conn *fc, struct fuse_req *req,
         req->io = io;
         req->end = fuse_aio_complete_req;
 
+        __fuse_get_request(req);
         fuse_request_send_background(fc, req);
 
         return num_bytes;
 }
 
-static size_t fuse_send_read(struct fuse_req *req, struct file *file,
+static size_t fuse_send_read(struct fuse_req *req, struct fuse_io_priv *io,
                              loff_t pos, size_t count, fl_owner_t owner)
 {
+        struct file *file = io->file;
         struct fuse_file *ff = file->private_data;
         struct fuse_conn *fc = ff->fc;
 
@@ -611,6 +613,10 @@ static size_t fuse_send_read(struct fuse_req *req, struct file *file,
                 inarg->read_flags |= FUSE_READ_LOCKOWNER;
                 inarg->lock_owner = fuse_lock_owner_id(fc, owner);
         }
+
+        if (io->async)
+                return fuse_async_req_send(fc, req, count, io);
+
         fuse_request_send(fc, req);
         return req->out.args[0].size;
 }
@@ -631,6 +637,7 @@ static void fuse_read_update_size(struct inode *inode, loff_t size,
 
 static int fuse_readpage(struct file *file, struct page *page)
 {
+        struct fuse_io_priv io = { .async = 0, .file = file };
         struct inode *inode = page->mapping->host;
         struct fuse_conn *fc = get_fuse_conn(inode);
         struct fuse_req *req;
@@ -663,7 +670,7 @@ static int fuse_readpage(struct file *file, struct page *page)
         req->num_pages = 1;
         req->pages[0] = page;
         req->page_descs[0].length = count;
-        num_read = fuse_send_read(req, file, pos, count, NULL);
+        num_read = fuse_send_read(req, &io, pos, count, NULL);
         err = req->out.h.error;
         fuse_put_request(fc, req);
 
@@ -873,9 +880,10 @@ static void fuse_write_fill(struct fuse_req *req, struct fuse_file *ff,
         req->out.args[0].value = outarg;
 }
 
-static size_t fuse_send_write(struct fuse_req *req, struct file *file,
+static size_t fuse_send_write(struct fuse_req *req, struct fuse_io_priv *io,
                               loff_t pos, size_t count, fl_owner_t owner)
 {
+        struct file *file = io->file;
         struct fuse_file *ff = file->private_data;
         struct fuse_conn *fc = ff->fc;
         struct fuse_write_in *inarg = &req->misc.write.in;
@@ -886,6 +894,10 @@ static size_t fuse_send_write(struct fuse_req *req, struct file *file,
                 inarg->write_flags |= FUSE_WRITE_LOCKOWNER;
                 inarg->lock_owner = fuse_lock_owner_id(fc, owner);
         }
+
+        if (io->async)
+                return fuse_async_req_send(fc, req, count, io);
+
         fuse_request_send(fc, req);
         return req->misc.write.out.size;
 }
@@ -909,11 +921,12 @@ static size_t fuse_send_write_pages(struct fuse_req *req, struct file *file,
         size_t res;
         unsigned offset;
         unsigned i;
+        struct fuse_io_priv io = { .async = 0, .file = file };
 
         for (i = 0; i < req->num_pages; i++)
                 fuse_wait_on_page_writeback(inode, req->pages[i]->index);
 
-        res = fuse_send_write(req, file, pos, count, NULL);
+        res = fuse_send_write(req, &io, pos, count, NULL);
 
         offset = req->page_descs[0].offset;
         count = res;
@@ -1251,10 +1264,11 @@ static inline int fuse_iter_npages(const struct iov_iter *ii_p)
         return min(npages, FUSE_MAX_PAGES_PER_REQ);
 }
 
-ssize_t fuse_direct_io(struct file *file, const struct iovec *iov,
+ssize_t fuse_direct_io(struct fuse_io_priv *io, const struct iovec *iov,
                        unsigned long nr_segs, size_t count, loff_t *ppos,
                        int write)
 {
+        struct file *file = io->file;
         struct fuse_file *ff = file->private_data;
         struct fuse_conn *fc = ff->fc;
         size_t nmax = write ? fc->max_write : fc->max_read;
@@ -1280,11 +1294,12 @@ ssize_t fuse_direct_io(struct file *file, const struct iovec *iov,
                 }
 
                 if (write)
-                        nres = fuse_send_write(req, file, pos, nbytes, owner);
+                        nres = fuse_send_write(req, io, pos, nbytes, owner);
                 else
-                        nres = fuse_send_read(req, file, pos, nbytes, owner);
+                        nres = fuse_send_read(req, io, pos, nbytes, owner);
 
-                fuse_release_user_pages(req, !write);
+                if (!io->async)
+                        fuse_release_user_pages(req, !write);
                 if (req->out.h.error) {
                         if (!res)
                                 res = req->out.h.error;
@@ -1314,16 +1329,18 @@ ssize_t fuse_direct_io(struct file *file, const struct iovec *iov,
 }
 EXPORT_SYMBOL_GPL(fuse_direct_io);
 
-static ssize_t __fuse_direct_read(struct file *file, const struct iovec *iov,
+static ssize_t __fuse_direct_read(struct fuse_io_priv *io,
+                                  const struct iovec *iov,
                                   unsigned long nr_segs, loff_t *ppos)
 {
         ssize_t res;
+        struct file *file = io->file;
         struct inode *inode = file_inode(file);
 
         if (is_bad_inode(inode))
                 return -EIO;
 
-        res = fuse_direct_io(file, iov, nr_segs, iov_length(iov, nr_segs),
+        res = fuse_direct_io(io, iov, nr_segs, iov_length(iov, nr_segs),
                              ppos, 0);
 
         fuse_invalidate_attr(inode);
@@ -1334,21 +1351,24 @@ static ssize_t __fuse_direct_read(struct file *file, const struct iovec *iov,
 static ssize_t fuse_direct_read(struct file *file, char __user *buf,
                                      size_t count, loff_t *ppos)
 {
+        struct fuse_io_priv io = { .async = 0, .file = file };
         struct iovec iov = { .iov_base = buf, .iov_len = count };
-        return __fuse_direct_read(file, &iov, 1, ppos);
+        return __fuse_direct_read(&io, &iov, 1, ppos);
 }
 
-static ssize_t __fuse_direct_write(struct file *file, const struct iovec *iov,
+static ssize_t __fuse_direct_write(struct fuse_io_priv *io,
+                                   const struct iovec *iov,
                                    unsigned long nr_segs, loff_t *ppos)
 {
+        struct file *file = io->file;
         struct inode *inode = file_inode(file);
         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, iov, nr_segs, count, ppos, 1);
-                if (res > 0)
+                res = fuse_direct_io(io, iov, nr_segs, count, ppos, 1);
+                if (!io->async && res > 0)
                         fuse_write_update_size(inode, *ppos);
         }
 
@@ -1363,13 +1383,14 @@ static ssize_t fuse_direct_write(struct file *file, const char __user *buf,
         struct iovec iov = { .iov_base = (void __user *)buf, .iov_len = count };
         struct inode *inode = file_inode(file);
         ssize_t res;
+        struct fuse_io_priv io = { .async = 0, .file = file };
 
         if (is_bad_inode(inode))
                 return -EIO;
 
         /* Don't allow parallel writes to the same file */
         mutex_lock(&inode->i_mutex);
-        res = __fuse_direct_write(file, &iov, 1, ppos);
+        res = __fuse_direct_write(&io, &iov, 1, ppos);
         mutex_unlock(&inode->i_mutex);
 
         return res;
@@ -2339,14 +2360,23 @@ fuse_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
         ssize_t ret = 0;
         struct file *file = NULL;
         loff_t pos = 0;
+        struct fuse_io_priv *io;
 
         file = iocb->ki_filp;
         pos = offset;
 
+        io = kzalloc(sizeof(struct fuse_io_priv), GFP_KERNEL);
+        if (!io)
+                return -ENOMEM;
+
+        io->file = file;
+
         if (rw == WRITE)
-                ret = __fuse_direct_write(file, iov, nr_segs, &pos);
+                ret = __fuse_direct_write(io, iov, nr_segs, &pos);
         else
-                ret = __fuse_direct_read(file, iov, nr_segs, &pos);
+                ret = __fuse_direct_read(io, iov, nr_segs, &pos);
+
+        kfree(io);
 
         return ret;
 }
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index aea072413c47..337169a406c9 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -732,6 +732,11 @@ struct fuse_req *fuse_get_req(struct fuse_conn *fc, unsigned npages);
 struct fuse_req *fuse_get_req_for_background(struct fuse_conn *fc,
                                              unsigned npages);
 
+/*
+ * Increment reference count on request
+ */
+void __fuse_get_request(struct fuse_req *req);
+
 /**
  * Get a request, may fail with -ENOMEM,
  * useful for callers who doesn't use req->pages[]
@@ -846,7 +851,7 @@ int fuse_reverse_inval_entry(struct super_block *sb, u64 parent_nodeid,
 
 int fuse_do_open(struct fuse_conn *fc, u64 nodeid, struct file *file,
                  bool isdir);
-ssize_t fuse_direct_io(struct file *file, const struct iovec *iov,
+ssize_t fuse_direct_io(struct fuse_io_priv *io, const struct iovec *iov,
                        unsigned long nr_segs, size_t count, loff_t *ppos,
                        int write);
 long fuse_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg,