diff options
Diffstat (limited to 'src/backend/storage/buffer/bufmgr.c')
| -rw-r--r-- | src/backend/storage/buffer/bufmgr.c | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c index 8647eddcb42..f47f1b66b1f 100644 --- a/src/backend/storage/buffer/bufmgr.c +++ b/src/backend/storage/buffer/bufmgr.c @@ -1929,6 +1929,35 @@ RelationGetNumberOfBlocksInFork(Relation relation, ForkNumber forkNum) return smgrnblocks(relation->rd_smgr, forkNum); } +/* + * BufferIsPermanent + * Determines whether a buffer will potentially still be around after + * a crash. Caller must hold a buffer pin. + */ +bool +BufferIsPermanent(Buffer buffer) +{ + volatile BufferDesc *bufHdr; + + /* Local buffers are used only for temp relations. */ + if (BufferIsLocal(buffer)) + return false; + + /* Make sure we've got a real buffer, and that we hold a pin on it. */ + Assert(BufferIsValid(buffer)); + Assert(BufferIsPinned(buffer)); + + /* + * BM_PERMANENT can't be changed while we hold a pin on the buffer, so + * we need not bother with the buffer header spinlock. Even if someone + * else changes the buffer header flags while we're doing this, we assume + * that changing an aligned 2-byte BufFlags value is atomic, so we'll read + * the old value or the new value, but not random garbage. + */ + bufHdr = &BufferDescriptors[buffer - 1]; + return (bufHdr->flags & BM_PERMANENT) != 0; +} + /* --------------------------------------------------------------------- * DropRelFileNodeBuffers * |