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Groups > linux.kernel > #1608250 > unrolled thread
| Started by | Denis Kirjanov <dkirjanov@cloudlinux.com> |
|---|---|
| First post | 2017-03-24 10:10 +0100 |
| Last post | 2017-03-25 07:50 +0100 |
| Articles | 3 — 2 participants |
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__link_block_group uses GFP_KERNEL Denis Kirjanov <dkirjanov@cloudlinux.com> - 2017-03-24 10:10 +0100
Re: __link_block_group uses GFP_KERNEL Jeff Mahoney <jeffm@suse.com> - 2017-03-25 00:20 +0100
Re: __link_block_group uses GFP_KERNEL Denis Kirjanov <dkirjanov@cloudlinux.com> - 2017-03-25 07:50 +0100
| From | Denis Kirjanov <dkirjanov@cloudlinux.com> |
|---|---|
| Date | 2017-03-24 10:10 +0100 |
| Subject | __link_block_group uses GFP_KERNEL |
| Message-ID | <toton-7Is-35@gated-at.bofh.it> |
Hi guys, Looks like that current code does GFP_KERNEL allocation inside __link_block_group. the function invokes kobject_add and internally creates sysfs files with the GFP_KERNEL flag set. But since do_chunk_alloc executes insides the btrfs transaction it's not allowed to sleep. Thanks!
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| From | Jeff Mahoney <jeffm@suse.com> |
|---|---|
| Date | 2017-03-25 00:20 +0100 |
| Message-ID | <toGEV-m5-13@gated-at.bofh.it> |
| In reply to | #1608250 |
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On 3/24/17 5:02 AM, Denis Kirjanov wrote: > Hi guys, > > Looks like that current code does GFP_KERNEL allocation inside > __link_block_group. > the function invokes kobject_add and internally creates sysfs files > with the GFP_KERNEL flag set. Yep, that's a bug. > But since do_chunk_alloc executes insides the btrfs transaction it's > not allowed to sleep. It's allowed to sleep but isn't allowed to do reclaim that involves file system writeback. Michal Hocko's allocation context idea would fix this, but it's not there yet, so we'll need to defer the kobject_add until we can use GFP_KERNEL. -Jeff -- Jeff Mahoney SUSE Labs
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| From | Denis Kirjanov <dkirjanov@cloudlinux.com> |
|---|---|
| Date | 2017-03-25 07:50 +0100 |
| Message-ID | <toNGp-5pq-1@gated-at.bofh.it> |
| In reply to | #1609019 |
On 3/25/17, Jeff Mahoney <jeffm@suse.com> wrote: > On 3/24/17 5:02 AM, Denis Kirjanov wrote: >> Hi guys, >> >> Looks like that current code does GFP_KERNEL allocation inside >> __link_block_group. >> the function invokes kobject_add and internally creates sysfs files >> with the GFP_KERNEL flag set. > > Yep, that's a bug. > >> But since do_chunk_alloc executes insides the btrfs transaction it's >> not allowed to sleep. > > It's allowed to sleep but isn't allowed to do reclaim that involves file > system writeback. Michal Hocko's allocation context idea would fix > this, but it's not there yet, so we'll need to defer the kobject_add > until we can use GFP_KERNEL. Ok, I see. Can you point out to the initial patchset? Thanks! > > -Jeff > > -- > Jeff Mahoney > SUSE Labs > >
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