Kent Overstreet 83d539b1b0 bcachefs: Fix check_snapshot_exists() restart handling
Codepaths that create entries in the snapshots btree currently call
bch2_mark_snapshot(), which updates the in-memory snapshot table, before
transaction commit.

This is because bch2_mark_snapshot() is an atomic trigger, run with
btree write locks held, and isn't allowed to fail - but it might need to
reallocate the table, hence we call it early when we're still allowed to
fail.

This is generally harmless - if we fail, we'll have left an entry in the
snapshots table around, but nothing will reference it and it'll get
overwritten if reused by another transaction.

But check_snapshot_exists(), which reconstructs snapshots when the
snapshots btree has been corrupted or lost, was erronously rechecking if
the snapshot exists inside the transaction commit loop - so on
transaction restart (in this case mem_realloced), the second iteration
would return without repairing.

This code needs some cleanup: splitting out a "maybe realloc snapshots
table" helper would have avoided this, that will be in the next patch.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2025-04-03 12:11:43 -04:00
2024-09-01 20:43:24 -07:00
2025-02-04 11:27:45 -05:00
2022-09-28 09:02:20 +02:00
2025-03-09 13:45:25 -10:00
2024-03-18 03:36:32 -06:00

Linux kernel
============

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