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docs: update kernel bugs table as of 5.12.3

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Two new tree mod log bugs #5 and #6 (uncovered by the zoned IO work,
though #6 has been seen in the wild on 5.10.29).

Tweak the next of some of the workarounds.

Signed-off-by: Zygo Blaxell <bees@furryterror.org>
This commit is contained in:
Zygo Blaxell
2021-05-28 23:58:43 -04:00
parent b2d4a07c6f
commit b083003cf7
1 changed files with 12 additions and 7 deletions
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19
docs/btrfs-kernel.md
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@@ -7,9 +7,9 @@ First, a warning that is not specific to bees:
severe regression that can lead to fatal metadata corruption.** severe regression that can lead to fatal metadata corruption.**
This issue is fixed in kernel 5.4.14 and later. This issue is fixed in kernel 5.4.14 and later.
**Recommended kernel versions for bees are 4.19, 5.4, 5.7, 5.8, 5.9, **Recommended kernel versions for bees are 4.19, 5.4, 5.10, 5.11, or 5.12,
5.10, or 5.11, with recent LTS and -stable updates.** The latest released with recent LTS and -stable updates.** The latest released kernel as
kernel as of this writing is 5.11.11. of this writing is 5.12.3.
4.14, 4.9, and 4.4 LTS kernels with recent updates are OK with 4.14, 4.9, and 4.4 LTS kernels with recent updates are OK with
some issues. Older kernels will be slower (a little slower or a lot some issues. Older kernels will be slower (a little slower or a lot
@@ -59,6 +59,8 @@ These bugs are particularly popular among bees users:
| 5.7 | 5.10 | kernel crash if balance receives fatal signal e.g. Ctrl-C | 5.4.93, 5.10.11, 5.11 and later | 18d3bff411c8 btrfs: don't get an EINTR during drop_snapshot for reloc | 5.7 | 5.10 | kernel crash if balance receives fatal signal e.g. Ctrl-C | 5.4.93, 5.10.11, 5.11 and later | 18d3bff411c8 btrfs: don't get an EINTR during drop_snapshot for reloc
| 5.10 | 5.10 | 20x write performance regression | 5.10.8, 5.11 and later | e076ab2a2ca7 btrfs: shrink delalloc pages instead of full inodes | 5.10 | 5.10 | 20x write performance regression | 5.10.8, 5.11 and later | e076ab2a2ca7 btrfs: shrink delalloc pages instead of full inodes
| 5.4 | 5.11 | spurious tree checker failures on extent ref hash | 5.11.5, 5.12 and later | 1119a72e223f btrfs: tree-checker: do not error out if extent ref hash doesn't match | 5.4 | 5.11 | spurious tree checker failures on extent ref hash | 5.11.5, 5.12 and later | 1119a72e223f btrfs: tree-checker: do not error out if extent ref hash doesn't match
| - | 5.11 | tree mod log issue #5 | 4.4.263, 4.9.263, 4.14.227, 4.19.183, 5.4.108, 5.10.26, 5.11.9, 5.12 and later | dbcc7d57bffc btrfs: fix race when cloning extent buffer during rewind of an old root
| - | 5.12 | tree mod log issue #6 | 4.14.233, 4.19.191, 5.4.118, 5.10.36, 5.11.20, 5.12.3, 5.13 and later | f9690f426b21 btrfs: fix race when picking most recent mod log operation for an old root
| 4.15 | - | spurious warnings from `fs/fs-writeback.c` when `flushoncommit` is enabled | - | workaround: comment out the `WARN_ON` | 4.15 | - | spurious warnings from `fs/fs-writeback.c` when `flushoncommit` is enabled | - | workaround: comment out the `WARN_ON`
"Last bad kernel" refers to that version's last stable update from "Last bad kernel" refers to that version's last stable update from
@@ -90,7 +92,10 @@ Workarounds for known kernel bugs
running both the `LOGICAL_INO` ioctl and btrfs balance at the same time, running both the `LOGICAL_INO` ioctl and btrfs balance at the same time,
which avoids kernel crashes on old kernel versions. which avoids kernel crashes on old kernel versions.
This workaround is not necessary for kernels 5.4.19, 5.5.3, 5.6 and later. The numbers for "tree mod log issue #" in the above table are arbitrary.
There are a lot of them, and they all behave fairly similarly.
This workaround is less necessary for kernels 5.4.19 and later.
* **Slow backrefs** (aka toxic extents): Under certain conditions, * **Slow backrefs** (aka toxic extents): Under certain conditions,
if the number of references to a single shared extent grows too if the number of references to a single shared extent grows too
@@ -107,7 +112,7 @@ Workarounds for known kernel bugs
This workaround is less necessary for kernels 5.4.96, 5.7 and later, This workaround is less necessary for kernels 5.4.96, 5.7 and later,
though it can still take 2 ms of CPU to resolve each extent ref on a though it can still take 2 ms of CPU to resolve each extent ref on a
fast machine. fast machine on a large, heavily fragmented file.
* **dedupe breaks `btrfs send` in old kernels**. The bees option * **dedupe breaks `btrfs send` in old kernels**. The bees option
`--workaround-btrfs-send` prevents any modification of read-only subvols `--workaround-btrfs-send` prevents any modification of read-only subvols
@@ -118,12 +123,12 @@ Workarounds for known kernel bugs
5.3.17, 5.4.4, 5.5 and later; however, some conflict between send 5.3.17, 5.4.4, 5.5 and later; however, some conflict between send
and dedupe still remains, so the workaround is still useful. and dedupe still remains, so the workaround is still useful.
`btrfs receive` is not affected by this issue. `btrfs receive` is not and has never been affected by this issue.
Unfixed kernel bugs Unfixed kernel bugs
------------------- -------------------
As of 5.11.11: As of 5.12.3:
* **The kernel does not permit `btrfs send` and dedupe to run at the * **The kernel does not permit `btrfs send` and dedupe to run at the
same time**. Recent kernels no longer crash, but now refuse one same time**. Recent kernels no longer crash, but now refuse one