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576477e73c
Recent versions of the Linux system header files cause xlogdefs.h to believe that open_datasync should be the default sync method, whereas formerly fdatasync was the default on Linux. open_datasync is a bad choice, first because it doesn't actually outperform fdatasync (in fact the reverse), and second because we try to use O_DIRECT with it, causing failures on certain filesystems (e.g., ext4 with data=journal option). This part of the patch is largely per a proposal from Marti Raudsepp. More extensive changes are likely to follow in HEAD, but this is as much change as we want to back-patch. Also clean up confusing code and incorrect documentation surrounding the fsync_writethrough option. Those changes shouldn't result in any actual behavioral change, but I chose to back-patch them anyway to keep the branches looking similar in this area. In 9.0 and HEAD, also do some copy-editing on the WAL Reliability documentation section. Back-patch to all supported branches, since any of them might get used on modern Linux versions.
22 lines
1 KiB
C
22 lines
1 KiB
C
/* src/include/port/linux.h */
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/*
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* As of July 2007, all known versions of the Linux kernel will sometimes
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* return EIDRM for a shmctl() operation when EINVAL is correct (it happens
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* when the low-order 15 bits of the supplied shm ID match the slot number
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* assigned to a newer shmem segment). We deal with this by assuming that
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* EIDRM means EINVAL in PGSharedMemoryIsInUse(). This is reasonably safe
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* since in fact Linux has no excuse for ever returning EIDRM; it doesn't
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* track removed segments in a way that would allow distinguishing them from
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* private ones. But someday that code might get upgraded, and we'd have
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* to have a kernel version test here.
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*/
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#define HAVE_LINUX_EIDRM_BUG
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/*
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* Set the default wal_sync_method to fdatasync. With recent Linux versions,
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* xlogdefs.h's normal rules will prefer open_datasync, which (a) doesn't
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* perform better and (b) causes outright failures on ext4 data=journal
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* filesystems, because those don't support O_DIRECT.
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*/
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#define PLATFORM_DEFAULT_SYNC_METHOD SYNC_METHOD_FDATASYNC
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