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Make BufferIsExclusiveLocked and BufferIsDirty work for local buffers.

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These functions tried to check the state of the buffer's content lock
even for local buffers.  Since we don't use the content lock for a
local buffer, that would lead to a "false" result from
LWLockHeldByMeInMode, which would mean a misleading "false" answer
from BufferIsExclusiveLocked (we'd rather that case always return
"true") or an assertion failure in BufferIsDirty.

The core code never applies these two functions to local buffers,
and apparently no extensions do either, since we've not heard
complaints.  Still, in the name of future-proofing, let's fix
them to act as though a pinned local buffer is content-locked.

Author: Srinath Reddy <srinath2133@gmail.com>
Discussion: https://postgr.es/m/19396ef77f8.1098c4a1810508.2255483659262451647@zohocorp.com
This commit is contained in:
Tom Lane 2025-01-29 13:23:31 -05:00
parent 128897b101
commit f6ff75f796
1 changed files with 11 additions and 11 deletions
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22
src/backend/storage/buffer/bufmgr.c
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@ -2472,20 +2472,19 @@ BufferIsExclusiveLocked(Buffer buffer)
{ {
BufferDesc *bufHdr; BufferDesc *bufHdr;
Assert(BufferIsPinned(buffer));
if (BufferIsLocal(buffer)) if (BufferIsLocal(buffer))
{ {
int bufid = -buffer - 1; /* Content locks are not maintained for local buffers. */
return true;
bufHdr = GetLocalBufferDescriptor(bufid);
} }
else else
{ {
bufHdr = GetBufferDescriptor(buffer - 1); bufHdr = GetBufferDescriptor(buffer - 1);
return LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
LW_EXCLUSIVE);
} }
Assert(BufferIsPinned(buffer));
return LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
LW_EXCLUSIVE);
} }
/* /*
@ -2501,21 +2500,22 @@ BufferIsDirty(Buffer buffer)
{ {
BufferDesc *bufHdr; BufferDesc *bufHdr;
Assert(BufferIsPinned(buffer));
if (BufferIsLocal(buffer)) if (BufferIsLocal(buffer))
{ {
int bufid = -buffer - 1; int bufid = -buffer - 1;
bufHdr = GetLocalBufferDescriptor(bufid); bufHdr = GetLocalBufferDescriptor(bufid);
/* Content locks are not maintained for local buffers. */
} }
else else
{ {
bufHdr = GetBufferDescriptor(buffer - 1); bufHdr = GetBufferDescriptor(buffer - 1);
Assert(LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
LW_EXCLUSIVE));
} }
Assert(BufferIsPinned(buffer));
Assert(LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
LW_EXCLUSIVE));
return pg_atomic_read_u32(&bufHdr->state) & BM_DIRTY; return pg_atomic_read_u32(&bufHdr->state) & BM_DIRTY;
} }