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From: David Sterba <dsterba@suse.cz>
To: fdmanana@kernel.org
Cc: linux-btrfs@vger.kernel.org
Subject: Re: [PATCH v2] Btrfs: fix file corruption after snapshotting due to mix of buffered/DIO writes
Date: Wed, 27 Feb 2019 18:26:29 +0100
Message-ID: <20190227172629.GB24609@twin.jikos.cz> (raw)
In-Reply-To: <20190227134230.11860-1-fdmanana@kernel.org>

On Wed, Feb 27, 2019 at 01:42:30PM +0000, fdmanana@kernel.org wrote:
> @@ -1897,15 +1899,45 @@ static inline int btrfs_start_delalloc_flush(struct btrfs_fs_info *fs_info)
>  	 * from already being in a transaction and our join_transaction doesn't
>  	 * have to re-take the fs freeze lock.
>  	 */
> -	if (btrfs_test_opt(fs_info, FLUSHONCOMMIT))
> +	if (btrfs_test_opt(fs_info, FLUSHONCOMMIT)) {
>  		writeback_inodes_sb(fs_info->sb, WB_REASON_SYNC);
> +	} else {
> +		struct btrfs_pending_snapshot *pending;
> +		struct list_head *head = &trans->transaction->pending_snapshots;
> +
> +		/*
> +		 * Flush dellaloc for any root that is going to be snapshotted.
> +		 * This is done to avoid a corrupted version of files, in the
> +		 * snapshots, that had both buffered and direct IO writes (even
> +		 * if they were done sequentially) due to an unordered update of
> +		 * the inode's size on disk.
> +		 */
> +		list_for_each_entry(pending, head, list)
> +			btrfs_start_delalloc_snapshot(pending->root);
> +	}

A diff would be better than words, incremental on top of your patch:

@@ -1912,8 +1912,15 @@ static inline int btrfs_start_delalloc_flush(struct btrfs_trans_handle *trans)
                 * if they were done sequentially) due to an unordered update of
                 * the inode's size on disk.
                 */
-               list_for_each_entry(pending, head, list)
-                       btrfs_start_delalloc_snapshot(pending->root);
+               list_for_each_entry(pending, head, list) {
+                       int ret;
+
+                       ret = btrfs_start_delalloc_snapshot(pending->root);
+                       if (ret < 0) {
+                               writeback_inodes_sb(fs_info->sb, WB_REASON_SYNC);
+                               break;
+                       }
+               }
        }
        return 0;
 }
---

Making a switch by the exact error is probably not necessary and wouldn't be
future proof anyway.

  reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-04 14:28 [PATCH] Btrfs: fix file corruption after snapshotting fdmanana
2019-02-18 17:11 ` David Sterba
2019-02-18 17:27   ` Filipe Manana
2019-02-27 12:47     ` David Sterba
2019-02-27 13:42       ` Filipe Manana
2019-02-27 17:19         ` David Sterba
2019-02-27 13:42 ` [PATCH v2] Btrfs: fix file corruption after snapshotting due to mix of buffered/DIO writes fdmanana
2019-02-27 17:26   ` David Sterba [this message]
2019-02-27 17:32     ` Filipe Manana
2019-02-27 18:31       ` David Sterba
2019-02-27 18:56         ` Filipe Manana
2019-03-12 17:13           ` David Sterba

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