helpers.linux.fs: add dentry_path_first_mount() #426
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osandov
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Aug 14, 2024
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I love the idea, but I'm not a fan of the name. One option would be to overload d_path even more so that it can take a dentry with no mount:
def d_path( # type: ignore # Need positional-only arguments.
arg1: Object, arg2: Optional[Object] = None
) -> bytes:
if arg2 is None:
try:
mnt = container_of(arg1.mnt, "struct mount", "mnt")
except AttributeError:
dentry = arg1
mnt = ... your code to find the first mount
else:
dentry = arg1.dentry.read_()
else:
mnt = container_of(arg1, "struct mount", "mnt")
dentry = arg2.read_()(And in that case, maybe underspecify which mount we choose in case we want a different heuristic later.)
What do you think?
That's even better! I am not 100% attached to the specific heuristic either. It's really just a way to get any path for a dentry that goes all the way down to the root filesystem. I'll update this, probably tomorrow though. Thanks! |
There are some diagnostic use cases where all one has is a dentry and no vfsmount. This is technically ambiguous, because a superblock may be mounted in several places due to bind mounts, filesystem namespaces, etc. The dentry's full path would depend on the specific mount point. But when we're doing debugging, we frequently just want any representative filesystem path for the dentry. It turns out that the kernel always puts new mountpoints at the end of the superblock's list of mounts, so the first one is likely to be the most relevant anyway. Thus, arbitrarily choosing this first mountpoint is a good way to get a representative path. Update d_path() to accept a single dentry as well. Signed-off-by: Stephen Brennan <[email protected]>
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This is a bit of a drive-by helper idea, inspired by something we have in drgn-tools. We frequently want a way to just convert a dentry to a path even if we don't know the vfsmount associated with the path we want. This helper is a good way to do it. Let me know your thoughts!