gadget: improve device lookup, add helper for mount point lookup #6873
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Look out for symlinks that point nowhere. The osutil.FileExists() helper already uses os.Stat() internally and that will catch symlinks pointing nowhere. However, add a safety check in case anyone tweaks the osutil implementation. Signed-off-by: Maciej Borzecki <maciej.zenon.borzecki@canonical.com>
Add a helper for locating mount points of given filesystem structure. Signed-off-by: Maciej Borzecki <maciej.zenon.borzecki@canonical.com>
It is in Go 1.12+ only. Signed-off-by: Maciej Borzecki <maciej.zenon.borzecki@canonical.com>
Signed-off-by: Maciej Borzecki <maciej.zenon.borzecki@canonical.com>
chipaca
approved these changes
May 16, 2019
zyga
reviewed
May 17, 2019
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Looks good, I've added one comment about a case where mount entries shadow older entries. I also wonder if the kind of lookup should not belong in osutil (with a helper function to match so that PositionedVolume can stay here), simply because of the fact that looking at mount table is tricky.
gadget/device_linux.go
Outdated
| return "", fmt.Errorf("cannot read mount info: %v", err) | ||
| } | ||
| for _, entry := range mountInfo { | ||
| if entry.MountSource != devpath || entry.FsType != ps.Filesystem { |
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I would add a small snippet like this here:
if mountPoint != "" && (mountPoint == entry.MountDir || strings.HasPrefix(mountPoint, entry.MountDir + "/")) {
// mount entry clobbers visibility to previously discovered match
mountPoint = "" // clobbered
}
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There's a break couple of lines down, so the loop will finish once a match is found. This makes me think, I should restructure the loop bit to make the lookup easier to read.
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Pushed an update, should be clearer now.
Signed-off-by: Maciej Borzecki <maciej.zenon.borzecki@canonical.com>
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Add a helper for a filesystem structure mount point lookup. Take a live core18 system, for a structure
EFI Systemdefined like this:we should be able to idenfity
/boot/efias its mount point.Improve the lookup of matching devices. Although
os.FileExists()already doesos.Stat()and that will catch symlinks pointing nowhere, try the belt and suspenders approach to be on the safe side should somebody tweak the implementation.cc @cmatsuoka