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Allow users to tag images in read/only image stores #881

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Apr 28, 2021
Merged

Allow users to tag images in read/only image stores #881

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31 changes: 31 additions & 0 deletions store.go
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Original file line number Diff line number Diff line change
Expand Up @@ -2115,6 +2115,37 @@ func (s *store) SetNames(id string, names []string) error {
return ristore.SetNames(id, deduped)
}

// Check is id refers to a RO Store
ristores, err := s.ROImageStores()
if err != nil {
return err
}
for _, s := range ristores {
store := s
store.RLock()
defer store.Unlock()
if modified, err := store.Modified(); modified || err != nil {
if err = store.Load(); err != nil {
return err
}
}
if i, err := store.Get(id); err == nil {
// Unlock R/O lock and lock with R/W lock
// Previous defer.Unlock() will free the new lock.
ristore.Unlock()
ristore.Lock()
if len(deduped) > 1 {
// Do not want to create image name in R/W storage
deduped = deduped[1:]
}
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Can someone walk me through what's going on from line 2135 to 2140?
Why is the lock we take on 2136 read-write if the lock taken at line 2107 was read-only?
Why do we drop the first (and only the first) name of the possibly many names that the image record in the read-only store has attached to it when adding a record to the read-write store that will include the new name? What happens when someone calls us without exactly the set of names in i.Names?

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The first name is the existing image, the follow on names are the names being tagged.
Since we did not find the first name in the Read/Write store, but only in the Read/Only store, we want to add the new names to the readwrite store. We need the read/write lock now, so close the existing read/only lock and create a read/write lock, and then create images with the new name.

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The existing image can have had multiple names attached to it, and there's no requirement that SetNames() include more names than were already set on the image. That sort of explains the > 1 test for me, but it sounds like you're making an assumption here that isn't correct.
The read-write store was already locked for writing on line 2107. I still don't see the point of releasing the lock on line 2135 only to reacquire it on the very next line.

_, err := ristore.Create(id, deduped, i.TopLayer, i.Metadata, i.Created, i.Digest)
if err == nil {
return ristore.Save()
}
return err
}
}

rcstore, err := s.ContainerStore()
if err != nil {
return err
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5 changes: 5 additions & 0 deletions tests/stores.bats
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Expand Up @@ -106,6 +106,11 @@ load helpers
[ "$status" -eq 0 ]
[ "$output" != "" ]

run storage --storage-opt ${STORAGE_DRIVER}.imagestore=${TESTDIR}/ro-root add-names -n newimage $lowerimage
[ "$status" -eq 0 ]
run storage --storage-opt ${STORAGE_DRIVER}.imagestore=${TESTDIR}/ro-root delete-image newimage
[ "$status" -eq 0 ]

# Create a container based on the lowerimage.
run storage --storage-opt ${STORAGE_DRIVER}.imagestore=${TESTDIR}/ro-root --debug=false create-container "$lowerimage"
[ "$status" -eq 0 ]
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