From: Omar Sandoval <osandov@xxxxxx> Hello, This series adds an AT_LINK_REPLACE flag to linkat() which allows atomically replacing the destination if it exists. This is a respin of an old series [1] that I was convinced to resend due to some recent interest [2][3]. Patch 1 adds a flags argument to i_ops->link() in preparation. Patch 2 adds the VFS support. Patch 3 fixes an inode leak in btrfs_link(), included in this series because it conflicts with patch 4. Patch 4 adds support for AT_LINK_REPLACE to Btrfs. I've also included a man-page patch (with an example program), an xfs_io patch, and an fstest. Some outstanding issues: - The Btrfs implementation does a d_drop() on the replaced dentry. We probably want a d_replace() helper for filesystems to use. - Should AT_LINK_REPLACE be limited to O_TMPFILE? In my opinion, the answer is no. After all, `ln -f` is not that exotic. - Should AT_LINK_REPLACE guarantee data integrity? Again, I think the answer is no. That's more suited to something like Amir's AT_ATOMIC proposal [4]. Changes since v3: - Rebased on v5.5. - Added patches 1 and 3. - Incorporated Al's feedback on various error cases in patch 2. - Renamed the flag to AT_LINK_REPLACE. Thanks! 1: https://lore.kernel.org/linux-fsdevel/cover.1524549513.git.osandov@xxxxxx/ 2: https://lore.kernel.org/linux-fsdevel/3326.1579019665@xxxxxxxxxxxxxxxxxxxxxx/ 3: https://lore.kernel.org/linux-fsdevel/364531.1579265357@xxxxxxxxxxxxxxxxxxxxxx/ 4: https://lore.kernel.org/linux-fsdevel/20190527172655.9287-1-amir73il@xxxxxxxxx/ Cc: David Howells <dhowells@xxxxxxxxxx> Cc: Amir Goldstein <amir73il@xxxxxxxxx> Cc: Xi Wang <xi@xxxxxxxxxxxxxxxxx> Omar Sandoval (4): fs: add flags argument to i_op->link() fs: add AT_LINK_REPLACE flag for linkat() which replaces the target Btrfs: fix inode reference count leak in btrfs_link() error path Btrfs: add support for linkat() AT_REPLACE fs/9p/vfs_inode.c | 5 +- fs/9p/vfs_inode_dotl.c | 5 +- fs/affs/affs.h | 2 +- fs/affs/namei.c | 6 +- fs/afs/dir.c | 7 +- fs/bad_inode.c | 2 +- fs/bfs/dir.c | 7 +- fs/btrfs/inode.c | 70 ++++++++++++++-- fs/ceph/dir.c | 5 +- fs/cifs/cifsfs.h | 2 +- fs/cifs/link.c | 5 +- fs/coda/dir.c | 5 +- fs/ecryptfs/inode.c | 7 +- fs/ext2/namei.c | 5 +- fs/ext4/namei.c | 7 +- fs/f2fs/namei.c | 5 +- fs/fuse/dir.c | 5 +- fs/gfs2/inode.c | 5 +- fs/hfsplus/dir.c | 5 +- fs/hostfs/hostfs_kern.c | 5 +- fs/jffs2/dir.c | 8 +- fs/jfs/namei.c | 7 +- fs/libfs.c | 6 +- fs/minix/namei.c | 5 +- fs/namei.c | 166 +++++++++++++++++++++++++++++-------- fs/nfs/dir.c | 6 +- fs/nfs/internal.h | 2 +- fs/nfsd/vfs.c | 2 +- fs/nilfs2/namei.c | 5 +- fs/ocfs2/namei.c | 6 +- fs/overlayfs/dir.c | 5 +- fs/overlayfs/overlayfs.h | 2 +- fs/reiserfs/namei.c | 5 +- fs/sysv/namei.c | 7 +- fs/ubifs/dir.c | 5 +- fs/udf/namei.c | 5 +- fs/ufs/namei.c | 5 +- fs/xfs/xfs_iops.c | 6 +- include/linux/fs.h | 6 +- include/uapi/linux/fcntl.h | 1 + mm/shmem.c | 6 +- 41 files changed, 341 insertions(+), 90 deletions(-) -- 2.25.0
