From 439ee5f0c5080d4fd15fda0c5bbee1fb3a57894e Mon Sep 17 00:00:00 2001 From: Maxim Patlasov Date: Fri, 14 Dec 2012 19:21:26 +0400 Subject: [PATCH] fuse: optimize short direct reads If user requested direct read beyond EOF, we can skip sending fuse requests for positions beyond EOF because userspace would ACK them with zero bytes read anyway. We can trust to i_size in fuse_direct_IO for such cases because it's called from fuse_file_aio_read() and the latter updates fuse attributes including i_size. Signed-off-by: Maxim Patlasov Signed-off-by: Miklos Szeredi --- fs/fuse/file.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/fs/fuse/file.c b/fs/fuse/file.c index ba1d50369c24..8f39f7b8cef2 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -1331,7 +1331,8 @@ EXPORT_SYMBOL_GPL(fuse_direct_io); static ssize_t __fuse_direct_read(struct fuse_io_priv *io, const struct iovec *iov, - unsigned long nr_segs, loff_t *ppos) + unsigned long nr_segs, loff_t *ppos, + size_t count) { ssize_t res; struct file *file = io->file; @@ -1340,8 +1341,7 @@ static ssize_t __fuse_direct_read(struct fuse_io_priv *io, if (is_bad_inode(inode)) return -EIO; - res = fuse_direct_io(io, iov, nr_segs, iov_length(iov, nr_segs), - ppos, 0); + res = fuse_direct_io(io, iov, nr_segs, count, ppos, 0); fuse_invalidate_attr(inode); @@ -1353,7 +1353,7 @@ static ssize_t fuse_direct_read(struct file *file, char __user *buf, { struct fuse_io_priv io = { .async = 0, .file = file }; struct iovec iov = { .iov_base = buf, .iov_len = count }; - return __fuse_direct_read(&io, &iov, 1, ppos); + return __fuse_direct_read(&io, &iov, 1, ppos, count); } static ssize_t __fuse_direct_write(struct fuse_io_priv *io, @@ -2369,6 +2369,13 @@ fuse_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov, inode = file->f_mapping->host; i_size = i_size_read(inode); + /* optimization for short read */ + if (rw != WRITE && offset + count > i_size) { + if (offset >= i_size) + return 0; + count = i_size - offset; + } + io = kmalloc(sizeof(struct fuse_io_priv), GFP_KERNEL); if (!io) return -ENOMEM; @@ -2392,13 +2399,13 @@ fuse_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov, * to wait on real async I/O requests, so we must submit this request * synchronously. */ - if (!is_sync_kiocb(iocb) && (offset + count > i_size) && rw == WRITE) + if (!is_sync_kiocb(iocb) && (offset + count > i_size)) io->async = false; if (rw == WRITE) ret = __fuse_direct_write(io, iov, nr_segs, &pos); else - ret = __fuse_direct_read(io, iov, nr_segs, &pos); + ret = __fuse_direct_read(io, iov, nr_segs, &pos, count); if (io->async) { fuse_aio_complete(io, ret < 0 ? ret : 0, -1); -- GitLab