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From: David Sterba <dsterba@suse.cz>
To: Nikolay Borisov <nborisov@suse.com>
Cc: linux-btrfs@vger.kernel.org
Subject: Re: [PATCHv3] btrfs: Fix error handling in btrfs_cleanup_ordered_extents
Date: Wed, 5 Dec 2018 17:13:39 +0100
Message-ID: <20181205161339.GC3905@twin.jikos.cz> (raw)
In-Reply-To: <20181121151052.18744-1-nborisov@suse.com>

On Wed, Nov 21, 2018 at 05:10:52PM +0200, Nikolay Borisov wrote:
> Running btrfs/124 in a loop hung up on me sporadically with the
> following call trace:
> 	btrfs           D    0  5760   5324 0x00000000
> 	Call Trace:
> 	 ? __schedule+0x243/0x800
> 	 schedule+0x33/0x90
> 	 btrfs_start_ordered_extent+0x10c/0x1b0 [btrfs]
> 	 ? wait_woken+0xa0/0xa0
> 	 btrfs_wait_ordered_range+0xbb/0x100 [btrfs]
> 	 btrfs_relocate_block_group+0x1ff/0x230 [btrfs]
> 	 btrfs_relocate_chunk+0x49/0x100 [btrfs]
> 	 btrfs_balance+0xbeb/0x1740 [btrfs]
> 	 btrfs_ioctl_balance+0x2ee/0x380 [btrfs]
> 	 btrfs_ioctl+0x1691/0x3110 [btrfs]
> 	 ? lockdep_hardirqs_on+0xed/0x180
> 	 ? __handle_mm_fault+0x8e7/0xfb0
> 	 ? _raw_spin_unlock+0x24/0x30
> 	 ? __handle_mm_fault+0x8e7/0xfb0
> 	 ? do_vfs_ioctl+0xa5/0x6e0
> 	 ? btrfs_ioctl_get_supported_features+0x30/0x30 [btrfs]
> 	 do_vfs_ioctl+0xa5/0x6e0
> 	 ? entry_SYSCALL_64_after_hwframe+0x3e/0xbe
> 	 ksys_ioctl+0x3a/0x70
> 	 __x64_sys_ioctl+0x16/0x20
> 	 do_syscall_64+0x60/0x1b0
> 	 entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> This happens because during page writeback it's valid for
> writepage_delalloc to instantiate a delalloc range which doesn't
> belong to the page currently being written back.
> 
> The reason this case is valid is due to find_lock_delalloc_range
> returning any available range after the passed delalloc_start and
> ignorting whether the page under writeback is within that range.
> In turn ordered extents (OE) are always created for the returned range
> from find_lock_delalloc_range. If, however, a failure occurs while OE
> are being created then the clean up code in btrfs_cleanup_ordered_extents
> will be called.
> 
> Unfortunately the code in btrfs_cleanup_ordered_extents doesn't consider
> the case of such 'foreign' range being processed and instead it always
> assumes that the range OE are created for belongs to the page. This
> leads to the first page of such foregin range to not be cleaned up since
> it's deliberately missed skipped by the current cleaning up code.
> 
> Fix this by correctly checking whether the current page belongs to the
> range being instantiated and if so adjsut the range parameters
> passed for cleaning up. If it doesn't, then just clean the whole OE
> range directly.
> 
> Signed-off-by: Nikolay Borisov <nborisov@suse.com>
> Reviewed-by: Josef Bacik <josef@toxicpanda.com>

Added to misc-next, thanks.

      parent reply index

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-21 15:10 Nikolay Borisov
2018-12-04 16:28 ` Nikolay Borisov
2018-12-05 16:13 ` David Sterba [this message]

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