Re: [PATCH 1/3] Btrfs: don't skip the page flush since the enospc is not brought by it

[Josef Bacik <jbacik@fb.com>]

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On 02/27/2014 12:58 AM, Miao Xie wrote:
> As we know, btrfs flushes the continuous pages as many as
> possible, but if all the free spaces are small, we will allocate
> the spaces by several times, and if there is something wrong with
> the space reservation, it is very likely that some allocations
> succeed and the others fail. But the current code doesn't take this
> case into account, and set the error flag for the pages though
> their spaces are allocated successfully. It introduces a problem
> that we can not umount the fs after the above problem happens
> because we need wait for the flush of those pages whose spaces are
> allocated. This patch fixes the above problem, and makes the btrfs
> developers happy when they investigate the problem of the space
> reservation.
> 
> Signed-off-by: Miao Xie <miaox@cn.fujitsu.com> --- 
> fs/btrfs/extent_io.c | 15 +++++++++++++-- 1 file changed, 13
> insertions(+), 2 deletions(-)
> 
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index
> fbe501d..97595ea 100644 --- a/fs/btrfs/extent_io.c +++
> b/fs/btrfs/extent_io.c @@ -3198,8 +3198,19 @@ static int
> __extent_writepage(struct page *page, struct writeback_control
> *wbc, &nr_written); /* File system has been set read-only */ if
> (ret) { -				SetPageError(page); -				goto done; +				/* +				 *
> Private2 means we allocate the space +				 * for this page
> successfully, and enospc +				 * error doesn't set the fs to be
> R/O, so +				 * we can write out the page and needn't +				 * set
> error flag for this page. If so, we +				 * can prevent the umount
> task from being +				 * blocked. +				 */ +				if (!(ret == -ENOSPC
> && PagePrivate2(page))) { +					SetPageError(page); +					goto
> done; +				}

So now we just ignore ret == -ENOSPC, we still need to return this
back to the caller.  Thanks,

Josef

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