[1/5] xfs: make attr lookup returns consistent

Commit Message

Dave Chinner Aug. 29, 2019, 11:35 a.m. UTC

From: Dave Chinner <[e-mail]>

Shortform, leaf and remote value attr value retrieval return
different values for success. This makes it more complex to handle
actual errors xfs_attr_get() as some errors mean success and some
mean failure. Make the return values consistent for success and
failure consistent for all attribute formats.

Signed-off-by: Dave Chinner <[e-mail]>
Reviewed-by: Darrick J. Wong <[e-mail]>
---
 fs/xfs/libxfs/xfs_attr.c        | 55 +++++++++++++++++++++------------
 fs/xfs/libxfs/xfs_attr_leaf.c   | 15 ++++++---
 fs/xfs/libxfs/xfs_attr_remote.c |  2 ++
 fs/xfs/scrub/attr.c             |  2 --
 4 files changed, 48 insertions(+), 26 deletions(-)

Comments

Christoph Hellwig Aug. 30, 2019, 5:34 a.m. UTC | #1

On Thu, Aug 29, 2019 at 09:35:01PM +1000, Dave Chinner wrote:
> +/*
> + * Retrieve an extended attribute and its value.  Must have ilock.
> + * Returns 0 on successful retrieval, otherwise an error.
> + */
>  int
>  xfs_attr_get_ilocked(

This just updates a comment on xfs_attr_get_ilocked, no other change,
so looks good.

>
>  	struct xfs_inode	*ip,
> @@ -147,7 +150,7 @@ xfs_attr_get(
>  	xfs_iunlock(ip, lock_mode);
>  
>  	*valuelenp = args.valuelen;
> -	return error == -EEXIST ? 0 : error;
> +	return error;
>  }

This drops a conversion from -EEXIST to 0 at the very top of the
callchain.

> -	if (!error && (args->rmtblkno > 0) && !(args->flags & ATTR_KERNOVAL)) {
> -		error = xfs_attr_rmtval_get(args);
> -	}
> -	return error;
> +	if (error)
> +		return error;
> +
> +	/* check if we have to retrieve a remote attribute to get the value */
> +	if (args->flags & ATTR_KERNOVAL)
> +		return 0;
> +	if (!args->rmtblkno)
> +		return 0;
> +	return xfs_attr_rmtval_get(args);

No change at all here, just a more verbose style.

>  STATIC int
>  xfs_attr_node_get(xfs_da_args_t *args)
> @@ -1294,24 +1306,27 @@ xfs_attr_node_get(xfs_da_args_t *args)
>  	error = xfs_da3_node_lookup_int(state, &retval);
>  	if (error) {
>  		retval = error;
> -	} else if (retval == -EEXIST) {
> -		blk = &state->path.blk[ state->path.active-1 ];
> -		ASSERT(blk->bp != NULL);
> -		ASSERT(blk->magic == XFS_ATTR_LEAF_MAGIC);
> -
> -		/*
> -		 * Get the value, local or "remote"
> -		 */
> -		retval = xfs_attr3_leaf_getvalue(blk->bp, args);
> -		if (!retval && (args->rmtblkno > 0)
> -		    && !(args->flags & ATTR_KERNOVAL)) {
> -			retval = xfs_attr_rmtval_get(args);
> -		}
> +		goto out_release;
>  	}
> +	if (retval != -EEXIST)
> +		goto out_release;
> +
> +	/*
> +	 * Get the value, local or "remote"
> +	 */
> +	blk = &state->path.blk[state->path.active - 1];
> +	retval = xfs_attr3_leaf_getvalue(blk->bp, args);
> +	if (retval)
> +		goto out_release;
> +	if (args->flags & ATTR_KERNOVAL)
> +		goto out_release;
> +	if (args->rmtblkno > 0)
> +		retval = xfs_attr_rmtval_get(args);
>  
>  	/*
>  	 * If not in a transaction, we have to release all the buffers.
>  	 */
> +out_release:

No change at all here as far as I can tell, just using a goto to
unwind error handling, and rewriting some code to be less
dense/obsfucated.

>  int
>  xfs_attr_shortform_getvalue(xfs_da_args_t *args)
>  {
> @@ -743,7 +746,7 @@ xfs_attr_shortform_getvalue(xfs_da_args_t *args)
>  			continue;
>  		if (args->flags & ATTR_KERNOVAL) {
>  			args->valuelen = sfe->valuelen;
> -			return -EEXIST;
> +			return 0;
>  		}
>  		if (args->valuelen < sfe->valuelen) {
>  			args->valuelen = sfe->valuelen;
> @@ -752,7 +755,7 @@ xfs_attr_shortform_getvalue(xfs_da_args_t *args)
>  		args->valuelen = sfe->valuelen;
>  		memcpy(args->value, &sfe->nameval[args->namelen],
>  						    args->valuelen);
> -		return -EEXIST;
> +		return 0;

And here we have the first change - xfs_attr_shortform_getvalue now
returns 0 instead of -EEXIST when finding the xattr.  The old calling
conventions does indeed seem very odd.  As xfs_attr_shortform_getvalue
is directly called by the small xfs_attr_get_ilocked wrapper, which
only has two calers that fix up -EEXIST to 0 this looks safe.

So overall this looks good, but I think having this split into two
pure cleanups and one to actually switch this single case away from
-EEXIST (and document the chain as I wrote above while following it)
would have been more helpful.

So what:

Reviewed-by: Christoph Hellwig <[e-mail]>

Patch

diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
index d48fcf11cc35..32879ab11290 100644
--- a/fs/xfs/libxfs/xfs_attr.c
+++ b/fs/xfs/libxfs/xfs_attr.c
@@ -97,7 +97,10 @@  xfs_inode_hasattr(
  * Overall external interface routines.
  *========================================================================*/
 
-/* Retrieve an extended attribute and its value.  Must have ilock. */
+/*
+ * Retrieve an extended attribute and its value.  Must have ilock.
+ * Returns 0 on successful retrieval, otherwise an error.
+ */
 int
 xfs_attr_get_ilocked(
 	struct xfs_inode	*ip,
@@ -147,7 +150,7 @@  xfs_attr_get(
 	xfs_iunlock(ip, lock_mode);
 
 	*valuelenp = args.valuelen;
-	return error == -EEXIST ? 0 : error;
+	return error;
 }
 
 /*
@@ -768,6 +771,8 @@  xfs_attr_leaf_removename(
  *
  * This leaf block cannot have a "remote" value, we only call this routine
  * if bmap_one_block() says there is only one block (ie: no remote blks).
+ *
+ * Returns 0 on successful retrieval, otherwise an error.
  */
 STATIC int
 xfs_attr_leaf_get(xfs_da_args_t *args)
@@ -789,10 +794,15 @@  xfs_attr_leaf_get(xfs_da_args_t *args)
 	}
 	error = xfs_attr3_leaf_getvalue(bp, args);
 	xfs_trans_brelse(args->trans, bp);
-	if (!error && (args->rmtblkno > 0) && !(args->flags & ATTR_KERNOVAL)) {
-		error = xfs_attr_rmtval_get(args);
-	}
-	return error;
+	if (error)
+		return error;
+
+	/* check if we have to retrieve a remote attribute to get the value */
+	if (args->flags & ATTR_KERNOVAL)
+		return 0;
+	if (!args->rmtblkno)
+		return 0;
+	return xfs_attr_rmtval_get(args);
 }
 
 /*========================================================================
@@ -1268,11 +1278,13 @@  xfs_attr_refillstate(xfs_da_state_t *state)
 }
 
 /*
- * Look up a filename in a node attribute list.
+ * Retrieve the attribute data from a node attribute list.
  *
  * This routine gets called for any attribute fork that has more than one
  * block, ie: both true Btree attr lists and for single-leaf-blocks with
  * "remote" values taking up more blocks.
+ *
+ * Returns 0 on successful retrieval, otherwise an error.
  */
 STATIC int
 xfs_attr_node_get(xfs_da_args_t *args)
@@ -1294,24 +1306,27 @@  xfs_attr_node_get(xfs_da_args_t *args)
 	error = xfs_da3_node_lookup_int(state, &retval);
 	if (error) {
 		retval = error;
-	} else if (retval == -EEXIST) {
-		blk = &state->path.blk[ state->path.active-1 ];
-		ASSERT(blk->bp != NULL);
-		ASSERT(blk->magic == XFS_ATTR_LEAF_MAGIC);
-
-		/*
-		 * Get the value, local or "remote"
-		 */
-		retval = xfs_attr3_leaf_getvalue(blk->bp, args);
-		if (!retval && (args->rmtblkno > 0)
-		    && !(args->flags & ATTR_KERNOVAL)) {
-			retval = xfs_attr_rmtval_get(args);
-		}
+		goto out_release;
 	}
+	if (retval != -EEXIST)
+		goto out_release;
+
+	/*
+	 * Get the value, local or "remote"
+	 */
+	blk = &state->path.blk[state->path.active - 1];
+	retval = xfs_attr3_leaf_getvalue(blk->bp, args);
+	if (retval)
+		goto out_release;
+	if (args->flags & ATTR_KERNOVAL)
+		goto out_release;
+	if (args->rmtblkno > 0)
+		retval = xfs_attr_rmtval_get(args);
 
 	/*
 	 * If not in a transaction, we have to release all the buffers.
 	 */
+out_release:
 	for (i = 0; i < state->path.active; i++) {
 		xfs_trans_brelse(args->trans, state->path.blk[i].bp);
 		state->path.blk[i].bp = NULL;
diff --git a/fs/xfs/libxfs/xfs_attr_leaf.c b/fs/xfs/libxfs/xfs_attr_leaf.c
index 1408638c21c5..7a9440b7ab00 100644
--- a/fs/xfs/libxfs/xfs_attr_leaf.c
+++ b/fs/xfs/libxfs/xfs_attr_leaf.c
@@ -720,9 +720,12 @@  xfs_attr_shortform_lookup(xfs_da_args_t *args)
 }
 
 /*
- * Look up a name in a shortform attribute list structure.
+ * Retreive the attribute value and length.
+ *
+ * If ATTR_KERNOVAL is specified, only the length needs to be returned.
+ * Unlike a lookup, we only return an error if the attribute does not
+ * exist or we can't retrieve the value.
  */
-/*ARGSUSED*/
 int
 xfs_attr_shortform_getvalue(xfs_da_args_t *args)
 {
@@ -743,7 +746,7 @@  xfs_attr_shortform_getvalue(xfs_da_args_t *args)
 			continue;
 		if (args->flags & ATTR_KERNOVAL) {
 			args->valuelen = sfe->valuelen;
-			return -EEXIST;
+			return 0;
 		}
 		if (args->valuelen < sfe->valuelen) {
 			args->valuelen = sfe->valuelen;
@@ -752,7 +755,7 @@  xfs_attr_shortform_getvalue(xfs_da_args_t *args)
 		args->valuelen = sfe->valuelen;
 		memcpy(args->value, &sfe->nameval[args->namelen],
 						    args->valuelen);
-		return -EEXIST;
+		return 0;
 	}
 	return -ENOATTR;
 }
@@ -2350,6 +2353,10 @@  xfs_attr3_leaf_lookup_int(
 /*
  * Get the value associated with an attribute name from a leaf attribute
  * list structure.
+ *
+ * If ATTR_KERNOVAL is specified, only the length needs to be returned.
+ * Unlike a lookup, we only return an error if the attribute does not
+ * exist or we can't retrieve the value.
  */
 int
 xfs_attr3_leaf_getvalue(
diff --git a/fs/xfs/libxfs/xfs_attr_remote.c b/fs/xfs/libxfs/xfs_attr_remote.c
index 4eb30d357045..3e39b7d40f25 100644
--- a/fs/xfs/libxfs/xfs_attr_remote.c
+++ b/fs/xfs/libxfs/xfs_attr_remote.c
@@ -358,6 +358,8 @@  xfs_attr_rmtval_copyin(
 /*
  * Read the value associated with an attribute from the out-of-line buffer
  * that we stored it in.
+ *
+ * Returns 0 on successful retrieval, otherwise an error.
  */
 int
 xfs_attr_rmtval_get(
diff --git a/fs/xfs/scrub/attr.c b/fs/xfs/scrub/attr.c
index 922a5154e2b8..57dafb1665d9 100644
--- a/fs/xfs/scrub/attr.c
+++ b/fs/xfs/scrub/attr.c
@@ -163,8 +163,6 @@  xchk_xattr_listent(
 	args.valuelen = valuelen;
 
 	error = xfs_attr_get_ilocked(context->dp, &args);
-	if (error == -EEXIST)
-		error = 0;
 	if (!xchk_fblock_process_error(sx->sc, XFS_ATTR_FORK, args.blkno,
 			&error))
 		goto fail_xref;