Re: [PATCH v8 18/18] btrfs: minimal conversion to errseq_t writeback error reporting on fsync

[Jeff Layton]

On Thu, 2017-06-29 at 07:17 -0700, Christoph Hellwig wrote:
> On Thu, Jun 29, 2017 at 09:19:54AM -0400, jlay...@kernel.org wrote:
> > From: Jeff Layton 
> > 
> > Just check and advance the errseq_t in the file before returning.
> > Internal callers of filemap_* functions are left as-is.
> > 
> > Signed-off-by: Jeff Layton 
> > ---
> >  fs/btrfs/file.c | 7 +--
> >  1 file changed, 5 insertions(+), 2 deletions(-)
> > 
> > diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
> > index da1096eb1a40..1f57e1a523d9 100644
> > --- a/fs/btrfs/file.c
> > +++ b/fs/btrfs/file.c
> > @@ -2011,7 +2011,7 @@ int btrfs_sync_file(struct file *file, loff_t start, 
> > loff_t end, int datasync)
> > struct btrfs_root *root = BTRFS_I(inode)->root;
> > struct btrfs_trans_handle *trans;
> > struct btrfs_log_ctx ctx;
> > -   int ret = 0;
> > +   int ret = 0, err;
> > bool full_sync = 0;
> > u64 len;
> >  
> > @@ -2030,7 +2030,7 @@ int btrfs_sync_file(struct file *file, loff_t start, 
> > loff_t end, int datasync)
> >  */
> > ret = start_ordered_ops(inode, start, end);
> > if (ret)
> > -   return ret;
> > +   goto out;
> >  
> > inode_lock(inode);
> > atomic_inc(>log_batch);
> > @@ -2227,6 +2227,9 @@ int btrfs_sync_file(struct file *file, loff_t start, 
> > loff_t end, int datasync)
> > ret = btrfs_end_transaction(trans);
> > }
> >  out:
> > +   err = file_check_and_advance_wb_err(file);
> > +   if (!ret)
> > +   ret = err;
> > return ret > 0 ? -EIO : ret;
> 
> This means that we'll lose the exact error returned from
> start_ordered_ops.  Beyond that I can't really provide good feedback
> as the btrfs fsync code looks so much different from all the other
> fs fsync code..

Well, no...we'll keep the error from start_ordered_ops if there was one.
 We just advance the cursor past any stored error in that case without
returning it.

I have another fix for this patch too: there's a call to
filemap_check_errors in this function that I think should probably use
filemap_check_wb_err instead. Fixed in my tree.

I do agree though that while this works in my testing I'd like the btrfs
guys to ACK this as I don't fully grok the btrfs fsync code at all.
-- 
Jeff Layton 
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Re: [PATCH v8 18/18] btrfs: minimal conversion to errseq_t writeback error reporting on fsync

[Christoph Hellwig]

On Thu, Jun 29, 2017 at 09:19:54AM -0400, jlay...@kernel.org wrote:
> From: Jeff Layton 
> 
> Just check and advance the errseq_t in the file before returning.
> Internal callers of filemap_* functions are left as-is.
> 
> Signed-off-by: Jeff Layton 
> ---
>  fs/btrfs/file.c | 7 +--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
> index da1096eb1a40..1f57e1a523d9 100644
> --- a/fs/btrfs/file.c
> +++ b/fs/btrfs/file.c
> @@ -2011,7 +2011,7 @@ int btrfs_sync_file(struct file *file, loff_t start, 
> loff_t end, int datasync)
>   struct btrfs_root *root = BTRFS_I(inode)->root;
>   struct btrfs_trans_handle *trans;
>   struct btrfs_log_ctx ctx;
> - int ret = 0;
> + int ret = 0, err;
>   bool full_sync = 0;
>   u64 len;
>  
> @@ -2030,7 +2030,7 @@ int btrfs_sync_file(struct file *file, loff_t start, 
> loff_t end, int datasync)
>*/
>   ret = start_ordered_ops(inode, start, end);
>   if (ret)
> - return ret;
> + goto out;
>  
>   inode_lock(inode);
>   atomic_inc(>log_batch);
> @@ -2227,6 +2227,9 @@ int btrfs_sync_file(struct file *file, loff_t start, 
> loff_t end, int datasync)
>   ret = btrfs_end_transaction(trans);
>   }
>  out:
> + err = file_check_and_advance_wb_err(file);
> + if (!ret)
> + ret = err;
>   return ret > 0 ? -EIO : ret;

This means that we'll lose the exact error returned from
start_ordered_ops.  Beyond that I can't really provide good feedback
as the btrfs fsync code looks so much different from all the other
fs fsync code..
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