-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 27.05.2011 11:45, Hugo Mills wrote: > On Fri, May 27, 2011 at 10:30:29AM +0100, Stephane Chazelas wrote: >> 2011-05-27 10:12:24 +0100, Hugo Mills: >> [skipped useful clarification] >>> >>> That's all rather dense, and probably too much information. Hope >>> it's helpful, though. >> [...] >> >> It is, thanks. >> >> How would one end up in a situation where the output of "btrfs >> sub list ." has: >> >> ID 287 top level 285 path data >> >> How could a "subvolume 285" become a "top level"? > >> How does one get a subvolume with a top-level other than "5"? > > This just means that subvolume 287 was created (somewhere) inside > subvolume 285. > > Due to the way that the FS trees and subvolumes work, there's no > global namespace structure in btrfs; that is, there's no single data > structure that represents the entirety of the file/directory hierarchy > in the filesystem. Instead, it's broken up into these sub-namespaces > called subvolumes, and we only record parent/child relationships for > each subvolume separately. The "full path" you get from "btrfs subv > list" is reconstructed from that information in userspace(*). > > Hugo. > > (*) Here's how it does it: > > The userspace tool gets a list of every subvolume by looking at the FS > tree. It uses the corresponding back-refs to get the inode that > represents each of those FS trees inside its parent: > > Subvol inode in subvol > 256 991 5 > 257 896 256 > 258 1073 257 > > From the inode numbers, it can then recursively walk back up the > directory path to the top of each subvolume: > > Subvol inode in subvol relative path > 256 991 5 henry > 257 896 256 edward/mary > 258 1073 257 elizabeth > > From that, it can then reconstruct the full pathnames, by walking back > up the subvolume tree: > > subvol 258 is elizabeth in 257 > is edward/mary/elizabeth in 256 > is henry/edward/mary/elizabeth in 5 Just one (hopefully) short question: A line in the ouput of btrfs subvolume list like ID 257 top level 5 path test1/test1.1 says that the subvolume with name test1.1 (the last segment of the path) and ID 257 has the path test1/test1.1 starting at the top level subvolume which has ID 5 ?
Thanks, Andreas -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iQIcBAEBAgAGBQJN33ezAAoJEJIcBJ3+Xkgi3egP/25y7JjnHJ9ZfQ2TF0cVWlhh 4FSHKhXlokH7E8fMcBbwP6YTB2zJioRkdWKmzoNjAvLlL8QkI7PvljAipe7YMgai Zq+FNzN2y6qkpNBhdpJC0rnURbtD7neDdcRCDF3uatP2p+m6UghfPyTfqX31h1qc UOp+3r+HLvlhAtKILxRaIZHidpS9ThZyN2mFHyKbyMMCoFYRXlJwL8xurPWdInbQ sgjDmXVstsnoTcDaCsdWfUkRiLyPeiieOgCiB0X+/GdEG/gE6ICtzOf93fIeJu/B CdGoaOSz73UIPdXstqiawhKxB83Ly68GNfoc/mrjFEml91KalGUnq/6f/344u6mB 2Ipwn1dpeC5ImwZO+VEc1HSv/GPCWyotUFzjV8NB/CcYYehX8GiNY0cSaT0NjTzs ycUOOJUTWHTmavdT8ryDILPqSsqzMnN9NnrjJhs7EjEXSkvRxNQ4vUNOsWvCPjJl HlooInMQ8/QTBkBLPkkiHWmhNuUaMPH6DJ85v6RNpFLiyf9TFDzBJvvyrZbkWx2y tIvg8C1oKuZ1iulZidfY36h2wf4u/DuYgNYPSL0vsdOfABStn9MBeqPbqeF6fF42 AJ0gzVd+cqIWiFbnXEi4Zxt72l1DViLqe3Rxij2u00QOPRMtgGoKcwY7WmLKBnU5 1/vjmYvTJNnShewXMvsh =zCSk -----END PGP SIGNATURE----- -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
