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Do not use free space caching!

DISCUSSION Josef Bacik 4 participants 6 messages Mar 30, 2011 – Apr 1, 2011 Btrfs file system

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#0 lore raw

Hello,

Just found a big bug in the free space caching stuff that will result in early ENOSPC. I'm working on fixing this bug, but it won't be until tomorrow that I'll have it completely working, so for now make sure to mount -o clear_cache so that it just clears the cache and doesn't use it.

NOTE: It doesn't cause problems other than early ENOSPC, you won't get corruption or anything like that, tho you could possibly panic.

Sorry for the inconvenience. Thanks,

Josef

#1 lore raw
Quoted 11 lines · Josef Bacik

Hello,

Just found a big bug in the free space caching stuff that will result in early ENOSPC. I'm working on fixing this bug, but it won't be until tomorrow that I'll have it completely working, so for now make sure to mount -o clear_cache so that it just clears the cache and doesn't use it.

NOTE: It doesn't cause problems other than early ENOSPC, you won't get corruption or anything like that, tho you could possibly panic.

Sorry for the inconvenience. Thanks,

Any chance you could provide a little more information about which kernels are affected? Is it any kernel with free space cache support (is 2.6.38.x included?) - and if so, do you plan on submitting the fix to the stable kernel series?

Signature · 1 line
Calvin Walton <[email protected]>
#2 lore raw
Quoted 11 lines · Calvin Walton
Quoted 10 lines · Josef Bacik

Hello,

Just found a big bug in the free space caching stuff that will result in early ENOSPC. I'm working on fixing this bug, but it won't be until tomorrow that I'll have it completely working, so for now make sure to mount -o clear_cache so that it just clears the cache and doesn't use it.

NOTE: It doesn't cause problems other than early ENOSPC, you won't get corruption or anything like that, tho you could possibly panic.

Quoted 7 lines
Quoted 1 line

Sorry for the inconvenience. Thanks,

Any chance you could provide a little more information about which kernels are affected? Is it any kernel with free space cache support (is 2.6.38.x included?) - and if so, do you plan on submitting the fix to the stable kernel series?

Yeah it affects any kernel that has the free space cache feature, which I think started in .37. Course you have to have specifically enabled it, so it's not a huge problem. I've submitted a patch, but since it's currently an optional feature I don't think it needs to go to stable. Thanks,

Josef

#3 lore raw
Quoted 5 lines · Josef Bacik
Quoted 4 lines · Calvin Walton
Quoted 3 lines · Josef Bacik

Hello,

Just found a big bug in the free space caching stuff that will resu=

lt in

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early ENOSPC. I'm working on fixing this bug, but it won't be unti=

l

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tomorrow that I'll have it completely working, so for now make sure=

to

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mount -o clear_cache so that it just clears the cache and doesn't u=

se it.

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NOTE: It doesn't cause problems other than early ENOSPC, you won't =

get

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Quoted 5 lines
Quoted 3 lines

corruption or anything like that, tho you could possibly panic.

Sorry for the inconvenience. Thanks,

Any chance you could provide a little more information about which kernels are affected? Is it any kernel with free space cache support=

(is

Quoted 1 line
Quoted 1 line

2.6.38.x included?) - and if so, do you plan on submitting the fix t=

o

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the stable kernel series?

Yeah it affects any kernel that has the free space cache feature, whi=

ch I think

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started in .37. Course you have to have specifically enabled it, so =

it's not a

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huge problem. I've submitted a patch, but since it's currently an op=

tional

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feature I don't think it needs to go to stable. Thanks,

So it will have to wait for 2.6.39? If possible please push it for=20 inclusion it in the next stable of 2.6.38, as 2.6.39 is a few months=20 away and i wont risk an early RC for my system

Thanks

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Josef
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#4 lore raw
In reply to Josef Bacik
Quoted 9 lines · Josef Bacik
Quoted 7 lines · Calvin Walton
Quoted 6 lines · Josef Bacik

Hello,

Just found a big bug in the free space caching stuff that will result in early ENOSPC. I'm working on fixing this bug, but it won't be until tomorrow that I'll have it completely working, so for now make sure to mount -o clear_cache so that it just clears the cache and doesn't use it.

Quoted 4 lines

Yeah it affects any kernel that has the free space cache feature, which I think started in .37. Course you have to have specifically enabled it, so it's not a huge problem. I've submitted a patch, but since it's currently an optional feature I don't think it needs to go to stable. Thanks,

If you don't think the full fix is appropriate for the stable kernel, what about sending a simple patch to stable that just disables the free space caching support?

That should be enough to stop any adventurous users (of the kind who don't read mailing lists) from trying the free space caching support, and possibly hitting this bug.

Signature · 1 line
Calvin Walton <[email protected]>
#5 lore raw

Excerpts from Calvin Walton's message of 2011-04-01 13:56:51 -0400:

Quoted 15 lines · Josef Bacik
Quoted 9 lines · Calvin Walton
Quoted 7 lines · Josef Bacik
Quoted 6 lines

Hello,

Just found a big bug in the free space caching stuff that will result in early ENOSPC. I'm working on fixing this bug, but it won't be until tomorrow that I'll have it completely working, so for now make sure to mount -o clear_cache so that it just clears the cache and doesn't use it.

Quoted 4 lines

Yeah it affects any kernel that has the free space cache feature, which I think started in .37. Course you have to have specifically enabled it, so it's not a huge problem. I've submitted a patch, but since it's currently an optional feature I don't think it needs to go to stable. Thanks,

Quoted 8 lines

If you don't think the full fix is appropriate for the stable kernel, what about sending a simple patch to stable that just disables the free space caching support?

That should be enough to stop any adventurous users (of the kind who don't read mailing lists) from trying the free space caching support, and possibly hitting this bug.

We'll have a known stable patch for this shortly, I'd rather do that and send it back to the stable kernels.

-chris