Filesystems and case-insensitivity

Posted Nov 28, 2018 21:00 UTC (Wed) by smurf (subscriber, #17840)
In reply to: Filesystems and case-insensitivity by tnoo
Parent article: Filesystems and case-insensitivity

No, you can't do it in userspace. The kernel does not have directory locking, which you'd need for an atomic "create a file while making sure that there is no other file with the same name (case-insensitive)" operation. Thus if you create "makefile" you need to scan the whole directory for any other matching filename, and that *still* doesn't stop anybody from introducing consistency errors (you can race to create "Makefile" and "MakeFile" at the same time).

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Filesystems and case-insensitivity

Posted Nov 29, 2018 9:06 UTC (Thu) by dgm (subscriber, #49227) [Link] (2 responses)

> No, you can't do it in userspace. The kernel does not have directory locking, which you'd need for an atomic "create a file while making sure that there is no other file with the same name (case-insensitive)" operation.

Yes, you can. You only need to use the canonical representation of the file name (the case-folded one) and check that file name.

Filesystems and case-insensitivity

Posted Nov 29, 2018 12:20 UTC (Thu) by smurf (subscriber, #17840) [Link] (1 responses)

You presume that there *is* a canonical representation of a file name. For case-preserving file systems, there is no such thing.

Filesystems and case-insensitivity

Posted Nov 29, 2018 15:23 UTC (Thu) by dgm (subscriber, #49227) [Link]

Well, nobody was talking about case preservation, but now that you mention it, you have three options:
- use the filesystem as case preserving (and give up case insensitivity)
- use the filesystem as canse-insensitive (and forget about case preservation)
- use xattrs
And all that, without touching a single line of kernel code.