From: Omar Sandoval <osandov@xxxxxx> This is a proof-of-concept patch series implementing an AT_REPLACE flag for linkat(2) which allows us to replace the target. This is a nice primitive on its own, but it's most interesting when combined with O_TMPFILE, as it allows you to do an atomic update of a file with an O_TMPFILE. 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. Patch 2 adds a dcache helper for filesystem implementations of AT_REPLACE. I'm not entirely convinced that it's 100% correct. Patch 3 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. Any comments are welcome. Cc: Xi Wang <xi@xxxxxxxxxxxxxxxxx> Omar Sandoval (3): fs: add AT_REPLACE flag for linkat() which replaces the target vfs: add d_replace() Btrfs: add support for linkat() AT_REPLACE fs/btrfs/inode.c | 59 ++++++++++++++- fs/dcache.c | 68 +++++++++++++++-- fs/ecryptfs/inode.c | 2 +- fs/namei.c | 180 +++++++++++++++++++++++++++++++++++---------- fs/nfsd/vfs.c | 2 +- fs/overlayfs/overlayfs.h | 2 +- include/linux/dcache.h | 1 + include/linux/fs.h | 3 +- include/uapi/linux/fcntl.h | 1 + 9 files changed, 267 insertions(+), 51 deletions(-) -- 2.10.2 -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
