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pkg/mount.Mount: speedup (remove Mounted check)

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This was added in PR #6669 (commit f87afda123) because it was
otherwise impossible to do a re-mount of already mounted file system.

It is way better to just remove the Mounted() check altogether.

This change might potentially lead to multiple mounts to the same
mount point, so I audited all the users (except tests) and it looks
like no one is doing that:

 * volume/local maintains 'mounted' flag for every volume
 * pkg/chrootarchive already calls Mounted() before Mount()
   (so it actually parsed /proc/self/mountinfo twice, oops!)
 * daemon.mountVolumes() is called for docker cp only, and
   it is called once
 * daemon/graphdriver/zfs keeps track of 'mounted' status
 * daemon/graphdriver/devmapper: ditto
 * daemon.createSecretsDir() is only called once during container start

Surely I might have easily missed something so this needs a careful
review.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
This commit is contained in:
Kir Kolyshkin 2020-03-09 12:24:06 -07:00
parent d5595a5845
commit 83ed668688
1 changed files with 8 additions and 13 deletions
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21
pkg/mount/mount.go
View file

@ -97,24 +97,19 @@ func Mounted(mountpoint string) (bool, error) {
return len(entries) > 0, nil
}
// Mount will mount filesystem according to the specified configuration, on the
// condition that the target path is *not* already mounted. Options must be
// specified like the mount or fstab unix commands: "opt1=val1,opt2=val2". See
// flags.go for supported option flags.
// Mount will mount filesystem according to the specified configuration.
// Options must be specified like the mount or fstab unix commands:
// "opt1=val1,opt2=val2". See flags.go for supported option flags.
func Mount(device, target, mType, options string) error {
flag, data := parseOptions(options)
if flag&REMOUNT != REMOUNT {
if mounted, err := Mounted(target); err != nil || mounted {
return err
}
}
return mount(device, target, mType, uintptr(flag), data)
}
// ForceMount will mount a filesystem according to the specified configuration,
// *regardless* if the target path is not already mounted. Options must be
// specified like the mount or fstab unix commands: "opt1=val1,opt2=val2". See
// flags.go for supported option flags.
// Mount will mount filesystem according to the specified configuration.
// Options must be specified like the mount or fstab unix commands:
// "opt1=val1,opt2=val2". See flags.go for supported option flags.
//
// Deprecated: use Mount instead.
func ForceMount(device, target, mType, options string) error {
flag, data := parseOptions(options)
return mount(device, target, mType, uintptr(flag), data)