On 2017/12/14 22:13, Miklos Szeredi Wrote: > On Thu, Dec 14, 2017 at 7:47 AM, zhangyi (F) <yi.zhang@xxxxxxxxxx> wrote: >> fsck.overlay >> ============ >> >> fsck.overlay is used to check and optionally repair underlying >> directories of overlay-filesystem. > > Thanks for working on this. > > >> >> Check the following points: >> >> Whiteouts >> --------- >> >> A whiteout is a character device with 0/0 device number. It is used to >> record the removed files or directories, When a whiteout is found in a >> directory, there should be at least one directory or file with the same >> name in any of the corresponding lower layers. If not exist, the whiteout >> will be treated as orphan whiteout and remove. > > Okay. > >> >> Opaque directories >> ------------------ >> >> An opaque directory is a directory with "trusted.overlay.opaque" xattr >> valued "y". There are two legal situations of making opaque directory: 1) >> create directory over whiteout 2) creat directory in merged directory. If an >> opaque directory is found, corresponding matching name in lower layers might >> exist or parent directory might merged, If not, the opaque xattr will be >> treated as invalid and remove. > > Current version of overlay fs doesn't bother with removing opaque > attribute. So not sure fsck.overlay should care. Or at least is > should be an optional thing and not worth warning about, since it's > perfectly normal. > Indeed, we can introduce '-f' option to handle this (e2fsck(8)): -f Force checking even if the file system seems clean. >> >> Redirect directories >> -------------------- >> >> An redirect directory is a directory with "trusted.overlay.redirect" >> xattr valued to the path of the original location from the root of the >> overlay. It is only used when renaming a directory and "redirect dir" >> feature is enabled. If an redirect directory is found, the following >> must be met: >> >> 1) The directory store in redirect xattr should exist in one of lower >> layers. > > Okay. > >> 2) The origin directory should be redirected only once in one layer, >> which mean there is only one redirect xattr point to this origin directory in >> the specified layer. >> 3) A whiteout or an opaque directory with the same name to origin should >> exist in the same directory as the redirect directory. >> >> If not, 1) The redirect xattr is invalid and need to remove 2) One of >> the redirect xattr is redundant but not sure which one is, ask user 3) >> Create a whiteout device or set opaque xattr to an existing directory if the >> parent directory was meregd or remove xattr if not. > > Hmm, in this case also should ask the user, as it's not clear that the > "new" copy resulting from removal of whiteout on upper is the wanted > one or the "old" renamed copy. > Thanks for point this out, do you mean the newly created directory over whiteout between old renamed directory? If so, Amir have already pointed out in the first iteration and I handled it in current version. Please see: https://www.spinics.net/lists/linux-unionfs/msg03268.html Now, fsck will also check dir's redirect xattr for this case, it will add opaque xattr only when parent is merged and not redirected. >> >> Usage >> ===== >> >> 1. Ensure overlay filesystem is not mounted based on directories which >> need to check. >> >> 2. Run fsck.overlay program: >> Usage: >> fsck.overlay [-l lowerdir] [-u upperdir] [-w workdir] [-avhV] >> >> Options: >> -l, --lowerdir=LOWERDIR specify lower directories of overlayfs, >> multiple lower use ':' as separator. >> -u, --upperdir=UPPERDIR specify upper directory of overlayfs >> -w, --workdir=WORKDIR specify work directory of overlayfs > > Not sure what other fsck do, but I'd feel more logical to have the > same -olowerdir=..., etc. notation as for mount. > It's fine by me, I will change it for current version. Thanks, Yi. -- To unsubscribe from this list: send the line "unsubscribe linux-unionfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
