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jpillora / media-sort

Automatically organise your movies and tv series
MIT License
120 stars 21 forks source link

Add an 'mv' action which bangs out to '/bin/mv' to avoid bogus 'cross-device' issue #29

Open codeaholics opened 4 years ago

codeaholics commented 4 years ago

I appreciate this is likely to be controversial, so I understand if you don't want to merge it.

This commit adds a new mv action (--action). It simply execs /bin/mv.

The reason for this is that on BTRFS subvolumes (which my NAS uses), the Go os.Rename() call returns "invalid cross-device link", so the move() function falls back to making a new copy of the file and then deleting the original.

However, attempting the same move via the command line mv util works instantly. It turns out the BTRFS can make a copy-on-write copy of the file even though it's moving the file between sub-volumes. The mv util initially attempts a rename() syscall (which is the same as Go's os.Rename()), but if it gets EXDEV back then it falls back to making an ioctl call to make a copy-on-write copy.

The impact of this is that when moving large (4K) movies or whole TV series between BTRFS subvolumes, media-sort can take a very long time, while mv works instantly.

I've raised a bug report in Go (which has been effectively converted to an enhancement request): https://github.com/golang/go/issues/41487. In the meantime, this PR is a stop-gap measure.

jpillora commented 4 years ago

Thanks for the PR! Do posix systems all place mv under /bin? Is it better to use the abs path rather than do a PATH lookup?

codeaholics commented 4 years ago

I believe so, yes. I was surprised not to find it in /sbin. I guess we could do a path search, but that would be a lot more effort for what I don't believe would be a huge gain.