Messages in this thread Patch in this message | | | Subject | [PATCH 6/6] fuse: optimize short direct reads | From | "Maxim V. Patlasov" <> | Date | Mon, 10 Dec 2012 11:42:28 +0400 |
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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 <mpatlasov@parallels.com> --- fs/fuse/file.c | 19 +++++++++++++------ 1 files changed, 13 insertions(+), 6 deletions(-)
diff --git a/fs/fuse/file.c b/fs/fuse/file.c index 3e0fdb7..d2094e1 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -1324,7 +1324,7 @@ EXPORT_SYMBOL_GPL(fuse_direct_io); static ssize_t __fuse_direct_read(struct file *file, const struct iovec *iov, unsigned long nr_segs, loff_t *ppos, - struct kiocb *async) + struct kiocb *async, size_t count) { ssize_t res; struct inode *inode = file->f_path.dentry->d_inode; @@ -1332,8 +1332,7 @@ static ssize_t __fuse_direct_read(struct file *file, const struct iovec *iov, if (is_bad_inode(inode)) return -EIO; - res = fuse_direct_io(file, iov, nr_segs, iov_length(iov, nr_segs), - ppos, 0, async); + res = fuse_direct_io(file, iov, nr_segs, count, ppos, 0, async); fuse_invalidate_attr(inode); @@ -1344,7 +1343,7 @@ static ssize_t fuse_direct_read(struct file *file, char __user *buf, size_t count, loff_t *ppos) { struct iovec iov = { .iov_base = buf, .iov_len = count }; - return __fuse_direct_read(file, &iov, 1, ppos, NULL); + return __fuse_direct_read(file, &iov, 1, ppos, NULL, count); } static ssize_t __fuse_direct_write(struct file *file, const struct iovec *iov, @@ -2405,8 +2404,15 @@ 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; + } + /* cannot write beyond eof asynchronously */ - if (is_sync_kiocb(iocb) || (offset + count <= i_size) || rw != WRITE) { + if (is_sync_kiocb(iocb) || (offset + count <= i_size)) { struct fuse_io_priv *io; io = kmalloc(sizeof(struct fuse_io_priv), GFP_KERNEL); @@ -2429,7 +2435,8 @@ fuse_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov, if (rw == WRITE) ret = __fuse_direct_write(file, iov, nr_segs, &pos, async_cb); else - ret = __fuse_direct_read(file, iov, nr_segs, &pos, async_cb); + ret = __fuse_direct_read(file, iov, nr_segs, &pos, async_cb, + count); if (async_cb) { fuse_aio_complete(async_cb->private, ret == count ? 0 : -EIO,
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