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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Filipe Manana <fdmanana@suse.com>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.9 076/177] Btrfs: fix incorrect space accounting after failure to insert inline extent
Date:   Fri, 23 Mar 2018 10:53:24 +0100
Message-Id: <20180323094208.668814409@linuxfoundation.org>
In-Reply-To: <20180323094205.090519271@linuxfoundation.org>
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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Filipe Manana <fdmanana@suse.com>


[ Upstream commit 1c81ba237bcecad9bc885a1ddcf02d725ea38482 ]

When using compression, if we fail to insert an inline extent we
incorrectly end up attempting to free the reserved data space twice,
once through extent_clear_unlock_delalloc(), because we pass it the
flag EXTENT_DO_ACCOUNTING, and once through a direct call to
btrfs_free_reserved_data_space_noquota(). This results in a trace
like the following:

[  834.576240] ------------[ cut here ]------------
[  834.576825] WARNING: CPU: 2 PID: 486 at fs/btrfs/extent-tree.c:4316 btrfs_free_reserved_data_space_noquota+0x60/0x9f [btrfs]
[  834.579501] Modules linked in: btrfs crc32c_generic xor raid6_pq ppdev i2c_piix4 acpi_cpufreq psmouse tpm_tis parport_pc pcspkr serio_raw tpm_tis_core sg parport evdev i2c_core tpm button loop autofs4 ext4 crc16 jbd2 mbcache sr_mod cdrom sd_mod ata_generic virtio_scsi ata_piix virtio_pci libata virtio_ring virtio scsi_mod e1000 floppy [last unloaded: btrfs]
[  834.592116] CPU: 2 PID: 486 Comm: kworker/u32:4 Not tainted 4.10.0-rc8-btrfs-next-37+ #2
[  834.593316] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.1-0-gb3ef39f-prebuilt.qemu-project.org 04/01/2014
[  834.595273] Workqueue: btrfs-delalloc btrfs_delalloc_helper [btrfs]
[  834.596103] Call Trace:
[  834.596103]  dump_stack+0x67/0x90
[  834.596103]  __warn+0xc2/0xdd
[  834.596103]  warn_slowpath_null+0x1d/0x1f
[  834.596103]  btrfs_free_reserved_data_space_noquota+0x60/0x9f [btrfs]
[  834.596103]  compress_file_range.constprop.42+0x2fa/0x3fc [btrfs]
[  834.596103]  ? submit_compressed_extents+0x3a7/0x3a7 [btrfs]
[  834.596103]  async_cow_start+0x32/0x4d [btrfs]
[  834.596103]  btrfs_scrubparity_helper+0x187/0x3e7 [btrfs]
[  834.596103]  btrfs_delalloc_helper+0xe/0x10 [btrfs]
[  834.596103]  process_one_work+0x273/0x4e4
[  834.596103]  worker_thread+0x1eb/0x2ca
[  834.596103]  ? rescuer_thread+0x2b6/0x2b6
[  834.596103]  kthread+0x100/0x108
[  834.596103]  ? __list_del_entry+0x22/0x22
[  834.596103]  ret_from_fork+0x2e/0x40
[  834.611656] ---[ end trace 719902fe6bdef08f ]---

So fix this by not calling directly btrfs_free_reserved_data_space_noquota()
if an error happened.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/btrfs/inode.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -567,8 +567,10 @@ cont:
 						     PAGE_SET_WRITEBACK |
 						     page_error_op |
 						     PAGE_END_WRITEBACK);
-			btrfs_free_reserved_data_space_noquota(inode, start,
-						end - start + 1);
+			if (ret == 0)
+				btrfs_free_reserved_data_space_noquota(inode,
+							       start,
+							       end - start + 1);
 			goto free_pages_out;
 		}
 	}