From: Omar Sandoval <osandov@xxxxxx> Hi, Al, This is a respin of my linkat() AT_REPLACE series, previously posted here: https://patchwork.kernel.org/patch/9636735/ https://patchwork.kernel.org/patch/9636733/ There are no changes since v2, only a rebase onto v4.17-rc2 and some minor additions to the commit messages. The goal is to allow for updating a file atomically in-place with an O_TMPFILE like so: - open temporary file with O_TMPFILE - write temporary file contents - fsync temporary file - atomically replace permanent location with the temporary file - fsync parent directory Patch 1 implements the VFS support for this flag. The implementation resembles sys_renameat2(), and I took care to preserve all of the original error cases and make the new error cases consistent with rename. Previously, we discussed extending renameat2() instead of linkat() for this, but this makes a mess of rename and also forces us to special-case the parent directory for O_TMPFILEs in implementations of i_op->rename(), so I still think linkat() is a better fit. Patch 2 adds support for AT_REPLACE to Btrfs. That's the codebase I'm most familiar with so that's where I started, but it should be straightforward to implement for other filesystems. v1 of this series had some incorrect dentry fiddling, so now I just unhash the replaced dentry for simplicity. Please take a look. Thanks! Cc: Xi Wang <xi@xxxxxxxxxxxxxxxxx> Omar Sandoval (2): fs: add AT_REPLACE flag for linkat() which replaces the target Btrfs: add support for linkat() AT_REPLACE fs/btrfs/inode.c | 65 ++++++++++++- fs/ecryptfs/inode.c | 2 +- fs/namei.c | 181 +++++++++++++++++++++++++++++-------- fs/nfsd/vfs.c | 2 +- fs/overlayfs/overlayfs.h | 2 +- include/linux/fs.h | 3 +- include/uapi/linux/fcntl.h | 1 + 7 files changed, 211 insertions(+), 45 deletions(-) -- 2.17.0
