fs/macos: preserve the inode a rename overwrites#700
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The macOS virtio-fs passthrough addresses inodes by their volfs path
("/.vol/{dev}/{ino}"), which only resolves while the inode still has a
directory entry. A rename that REPLACES an existing target drops that
target's last link, but unlike do_unlink -- which stashes an fd to the
doomed inode in InodeData.unlinked_fd -- rename never preserved the
overwritten inode. Any FUSE op the guest later issues on it then resolves
a dangling volfs path and returns ENOENT.
This breaks the common atomic write-new-then-rename-over pattern when the
guest still holds the old target open: apt/dpkg rewrite /var/lib/dpkg/status
this way while apt holds it open, so apt's final close reports
"Problem closing the file /var/lib/dpkg/status - close (2: No such file or
directory)" even though the install succeeded. It reproduces on any
overlayfs upperdir backed by this server.
Mirror do_unlink: grab an fd to the target before renamex_np (replace case
only -- not RENAME_SWAP/RENAME_EXCL) and hand it to the displaced inode on
success. store_unlinked_fd now reports whether a tracked inode took
ownership so the caller closes the fd otherwise instead of leaking it.
Signed-off-by: Alex NOVAC <acdtrx@gmail.com>
acdtrx
requested review from
MatiasVara,
dorindabassey,
jakecorrenti,
mtjhrc,
slp and
tylerfanelli
as code owners
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The macOS virtio-fs passthrough addresses inodes by their volfs path ("/.vol/{dev}/{ino}"), which only resolves while the inode still has a directory entry. A rename that REPLACES an existing target drops that target's last link, but unlike do_unlink -- which stashes an fd to the doomed inode in InodeData.unlinked_fd -- rename never preserved the overwritten inode. Any FUSE op the guest later issues on it then resolves a dangling volfs path and returns ENOENT.
This breaks the common atomic write-new-then-rename-over pattern when the guest still holds the old target open: apt/dpkg rewrite /var/lib/dpkg/status this way while apt holds it open, so apt's final close reports "Problem closing the file /var/lib/dpkg/status - close (2: No such file or directory)" even though the install succeeded. It reproduces on any overlayfs upperdir backed by this server.
Mirror do_unlink: grab an fd to the target before renamex_np (replace case only -- not RENAME_SWAP/RENAME_EXCL) and hand it to the displaced inode on success. store_unlinked_fd now reports whether a tracked inode took ownership so the caller closes the fd otherwise instead of leaking it.
Built on macOS/aarch64 and verified in a downstream consumer — apt-based setup recipes that previously failed at dpkg's close now succeed.