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README: upgrade kernel requirement to 4.4.3 because of kernel bugs

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Zygo Blaxell
2016-12-07 22:01:45 -05:00
parent 1cd6263552
commit d82909387d
1 changed files with 14 additions and 7 deletions
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21
README.md
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@@ -223,20 +223,25 @@ Other Caveats
A Brief List Of Btrfs Kernel Bugs
---------------------------------
Fixed bugs:
Missing features (usually not available in older LTS kernels):
* 3.13: `FILE_EXTENT_SAME` ioctl added. No way to reliably dedup with
concurrent modifications before this.
* 3.16: `SEARCH_V2` ioctl added. Bees could use `SEARCH` instead.
* 4.2: `FILE_EXTENT_SAME` no longer updates mtime, can be used at EOF.
Kernel deadlock bugs fixed.
Bug fixes (sometimes included in older LTS kernels):
* 4.5: hang in the `INO_PATHS` ioctl used by Bees.
* 4.5: use-after-free in the `FILE_EXTENT_SAME` ioctl used by Bees.
* 4.7: *slow backref* bug no longer triggers a softlockup panic. It still
too long to resolve a block address to a root/inode/offset triple.
Fixed bugs not yet integrated in mainline Linux:
* 7f8e406 ("btrfs: improve delayed refs iterations"): reduces the cost
of LOGICAL_INO ioctl from 30-70% of bees running time to under 5%.
* 7f8e406 ("btrfs: improve delayed refs iterations"): significantly
reduces the CPU time cost of the LOGICAL_INO ioctl (from 30-70% of
bees running time to under 5%).
Unfixed kernel bugs (as of 4.5.7) with workarounds in Bees:
@@ -282,8 +287,10 @@ Unfixed kernel bugs (as of 4.5.7) with workarounds in Bees:
the filesystem after a crash). Alternatively, place BEESHOME on a
non-btrfs filesystem.
* If the fsync() BeesTempFile::make_copy is removed, the filesystem
hangs within a few hours, requiring a reboot to recover.
* If the `fsync()` in `BeesTempFile::make_copy` is removed, the filesystem
hangs within a few hours, requiring a reboot to recover. On the other
hand, there may be net performance benefits to calling `fsync()` before
or after each dedup. This needs further investigation.
Not really a bug, but a gotcha nonetheless:
@@ -314,7 +321,7 @@ Requirements
TODO: remove the one function used from this library.
It supports a feature Bees no longer implements.
* Linux kernel 4.2 or later
* Linux kernel 4.4.3 or later
Don't bother trying to make Bees work with older kernels.
It won't end well.