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btrfs: fix error handling in btrfs_dev_replace_start

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When we fail to start a transaction in btrfs_dev_replace_start, we leave
dev_replace->replace_start set to STARTED but clear ->srcdev and
->tgtdev.  Later, that can result in an Oops in
btrfs_dev_replace_progress when having state set to STARTED or SUSPENDED
implies that ->srcdev is valid.

Also fix error handling when the state is already STARTED or SUSPENDED
while starting.  That, too, will clear ->srcdev and ->tgtdev even though
it doesn't own them.  This should be an impossible case to hit since we
should be protected by the BTRFS_FS_EXCL_OP bit being set.  Let's add an
ASSERT there while we're at it.

Fixes: e93c89c1aaaaa (Btrfs: add new sources for device replace code)
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Jeff Mahoney 2018-09-06 15:52:17 -04:00 committed by David Sterba
parent c1766dd782
commit 5c06147128
1 changed files with 5 additions and 2 deletions
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7
fs/btrfs/dev-replace.c
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@ -440,6 +440,7 @@ int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info,
break;
case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
ASSERT(0);
ret = BTRFS_IOCTL_DEV_REPLACE_RESULT_ALREADY_STARTED;
goto leave;
}
@ -482,6 +483,10 @@ int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info,
if (IS_ERR(trans)) {
ret = PTR_ERR(trans);
btrfs_dev_replace_write_lock(dev_replace);
dev_replace->replace_state =
BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED;
dev_replace->srcdev = NULL;
dev_replace->tgtdev = NULL;
goto leave;
}
@ -503,8 +508,6 @@ int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info,
return ret;
leave:
dev_replace->srcdev = NULL;
dev_replace->tgtdev = NULL;
btrfs_dev_replace_write_unlock(dev_replace);
btrfs_destroy_dev_replace_tgtdev(tgt_device);
return ret;