On 02/02/2018 11:09 AM, Howard McLauchlan wrote:
> Presently, failing a primary super block write but succeeding in at
> least one super block write in general will appear to users as if
> nothing important went wrong. However, upon unmounting and re-mounting,
> the file system will be in a rolled back state. This was discovered
> with a BCC program that uses bpf_override_return() to fail super block
> writes.
>
> This patch outputs an error clarifying that the primary super block
> write has failed, so users can expect potentially erroneous behaviour.
> It also forces wait_dev_supers() to return an error to its caller if
> the primary super block write fails.
>
> Signed-off-by: Howard McLauchlan <hmclauch...@fb.com>
Reviewed-by: Qu Wenruo <w...@suse.com>
> ---
> V3: Rewrote boolean setting logic for clarity
> V2: Added devid to output, removed unnecessary fs_info parameter
>
> fs/btrfs/disk-io.c | 15 ++++++++++++++-
> 1 file changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index 5da18ebc9222..6ef32eb94669 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -3298,6 +3298,7 @@ static int wait_dev_supers(struct btrfs_device *device,
> int max_mirrors)
> struct buffer_head *bh;
> int i;
> int errors = 0;
> + bool primary_failed = false;
> u64 bytenr;
>
> if (max_mirrors == 0)
> @@ -3314,11 +3315,16 @@ static int wait_dev_supers(struct btrfs_device
> *device, int max_mirrors)
> BTRFS_SUPER_INFO_SIZE);
> if (!bh) {
> errors++;
> + if (i == 0)
> + primary_failed = true;
> continue;
> }
> wait_on_buffer(bh);
> - if (!buffer_uptodate(bh))
> + if (!buffer_uptodate(bh)) {
> errors++;
> + if (i == 0)
> + primary_failed = true;
> + }
>
> /* drop our reference */
> brelse(bh);
> @@ -3327,6 +3333,13 @@ static int wait_dev_supers(struct btrfs_device
> *device, int max_mirrors)
> brelse(bh);
> }
>
> + /* log error, force error return */
> + if (primary_failed) {
> + btrfs_err(device->fs_info, "error writing primary super block
> to device %llu",
> + device->devid);
> + return -1;
> + }
> +
> return errors < i ? 0 : -1;
> }
>
>
Forgot to add Qu's reviewed by
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