73 lines
2.9 KiB
Diff
73 lines
2.9 KiB
Diff
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From 2c39bd88a9b0db207c1158c76bbbe0b484dec9dd Mon Sep 17 00:00:00 2001
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From: Colin Walters <walters@verbum.org>
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Date: Fri, 3 Dec 2021 14:35:12 -0500
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Subject: [PATCH] repo: Change locking for summary regeneration to be shared
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This is trying to address:
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https://pagure.io/fedora-iot/issue/48
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Basically we changed rpm-ostree to start doing a shared lock during
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commit by default, but this broke because pungi is starting a process
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doing a commit for each architecture, and then trying to regenerate
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the summary after each one.
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This patch is deleting a big comment with a rationale for why
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summary regeneration should be exclusive. Point by point:
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> This makes sure the commits and deltas don't get
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> deleted while generating the summary.
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But prune operations require an exclusive lock, which means that
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data still can't be deleted when the summary grabs a shared lock.
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> It also means we can be sure refs
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> won't be created/updated/deleted during the operation, without having to
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> add exclusive locks to those operations which would prevent concurrent
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> commits from working.
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First: The status quo *has* prevented concurrent commits from working!
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There is no real locking solution to this problem. What we really
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need to do here is regenerate the summary after each commit *or*
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when the caller decides to do it and e.g. include deltas at the same
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time.
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It's OK if multiple threads race to regenerate the summary;
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last-one-wins behavior here is totally fine.
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---
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src/libostree/ostree-repo.c | 10 ++--------
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1 file changed, 2 insertions(+), 8 deletions(-)
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diff --git a/src/libostree/ostree-repo.c b/src/libostree/ostree-repo.c
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index 74cea37f2..a9be9f948 100644
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--- a/src/libostree/ostree-repo.c
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+++ b/src/libostree/ostree-repo.c
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@@ -6105,7 +6105,7 @@ summary_add_ref_entry (OstreeRepo *self,
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* and refs in %OSTREE_SUMMARY_COLLECTION_MAP are guaranteed to be in
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* lexicographic order.
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*
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- * Locking: exclusive
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+ * Locking: shared (Prior to 2021.7, this was exclusive)
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*/
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gboolean
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ostree_repo_regenerate_summary (OstreeRepo *self,
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@@ -6113,16 +6113,10 @@ ostree_repo_regenerate_summary (OstreeRepo *self,
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GCancellable *cancellable,
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GError **error)
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{
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- /* Take an exclusive lock. This makes sure the commits and deltas don't get
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- * deleted while generating the summary. It also means we can be sure refs
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- * won't be created/updated/deleted during the operation, without having to
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- * add exclusive locks to those operations which would prevent concurrent
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- * commits from working.
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- */
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g_autoptr(OstreeRepoAutoLock) lock = NULL;
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gboolean no_deltas_in_summary = FALSE;
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- lock = ostree_repo_auto_lock_push (self, OSTREE_REPO_LOCK_EXCLUSIVE,
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+ lock = ostree_repo_auto_lock_push (self, OSTREE_REPO_LOCK_SHARED,
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cancellable, error);
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if (!lock)
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return FALSE;
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