[PATCH v8 4/4] vfs: Add vfs_copy_file_range() support for pagecache copies
From: Anna Schumaker <hidden>
Date: 2015-11-06 21:28:10
Also in:
linux-btrfs, linux-fsdevel, linux-nfs
Subsystem:
filesystems (vfs and infrastructure), the rest · Maintainers:
Alexander Viro, Christian Brauner, Linus Torvalds
This allows us to have an in-kernel copy mechanism that avoids frequent switches between kernel and user space. This is especially useful so NFSD can support server-side copies. The default (flags=0) means to first attempt copy acceleration, but use the pagecache if that fails. I moved the rw_verify_area() calls into the fallback code since some filesystems can handle reflinking a large range. Signed-off-by: Anna Schumaker <redacted> Reviewed-by: Darrick J. Wong <redacted> Reviewed-by: Padraig Brady <redacted> Reviewed-by: Christoph Hellwig <hch@lst.de> --- fs/read_write.c | 37 ++++++++++++++++++++++++++----------- 1 file changed, 26 insertions(+), 11 deletions(-)
diff --git a/fs/read_write.c b/fs/read_write.c
index 97c15ca..a093830 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c@@ -1329,6 +1329,24 @@ COMPAT_SYSCALL_DEFINE4(sendfile64, int, out_fd, int, in_fd, } #endif +static ssize_t vfs_copy_fr_copy(struct file *file_in, loff_t pos_in, + struct file *file_out, loff_t pos_out, + size_t len) +{ + ssize_t ret = rw_verify_area(READ, file_in, &pos_in, len); + + if (ret >= 0) { + len = ret; + ret = rw_verify_area(WRITE, file_out, &pos_out, len); + if (ret >= 0) + len = ret; + } + if (ret < 0) + return ret; + + return do_splice_direct(file_in, &pos_in, file_out, &pos_out, len, 0); +} + /* * copy_file_range() differs from regular file read and write in that it * specifically allows return partial success. When it does so is up to
@@ -1345,17 +1363,9 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in, if (flags != 0) return -EINVAL; - /* copy_file_range allows full ssize_t len, ignoring MAX_RW_COUNT */ - ret = rw_verify_area(READ, file_in, &pos_in, len); - if (ret >= 0) - ret = rw_verify_area(WRITE, file_out, &pos_out, len); - if (ret < 0) - return ret; - if (!(file_in->f_mode & FMODE_READ) || !(file_out->f_mode & FMODE_WRITE) || - (file_out->f_flags & O_APPEND) || - !file_out->f_op->copy_file_range) + (file_out->f_flags & O_APPEND)) return -EBADF; /* this could be relaxed once a method supports cross-fs copies */
@@ -1369,8 +1379,13 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in, if (ret) return ret; - ret = file_out->f_op->copy_file_range(file_in, pos_in, file_out, pos_out, - len, flags); + ret = -EOPNOTSUPP; + if (file_out->f_op->copy_file_range) + ret = file_out->f_op->copy_file_range(file_in, pos_in, file_out, + pos_out, len, flags); + if (ret == -EOPNOTSUPP) + ret = vfs_copy_fr_copy(file_in, pos_in, file_out, pos_out, len); + if (ret > 0) { fsnotify_access(file_in); add_rchar(current, ret);
--
2.6.2