diff mbox

btrfs: use proper type for failrec in extent_state

Message ID 1455193453-14837-1-git-send-email-dsterba@suse.com (mailing list archive)
State Accepted
Headers show

Commit Message

David Sterba Feb. 11, 2016, 12:24 p.m. UTC 
We use the private member of extent_state to store the failrec and play
pointless pointer games.

Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/extent_io.c | 31 ++++++++++++++-----------------
 fs/btrfs/extent_io.h |  5 ++---
 2 files changed, 16 insertions(+), 20 deletions(-)

Comments

David Sterba Feb. 22, 2016, 5:58 p.m. UTC | #1 
On Thu, Feb 11, 2016 at 01:24:13PM +0100, David Sterba wrote:
> We use the private member of extent_state to store the failrec and play
> pointless pointer games.
> 
> Signed-off-by: David Sterba <dsterba@suse.com>

I'm not sure why, but my gcc 5.3.1 think's that a member of failrec can
be used uninitialized:

  CC [M]  fs/btrfs/extent_io.o
fs/btrfs/extent_io.c: In function ‘clean_io_failure’:
fs/btrfs/extent_io.c:2133:4: warning: ‘failrec’ may be used uninitialized in this function [-Wmaybe-uninitialized]
    repair_io_failure(inode, start, failrec->len,
    ^

which points to:

2126         if (state && state->start <= failrec->start &&
2127             state->end >= failrec->start + failrec->len - 1) {
2128                 num_copies = btrfs_num_copies(fs_info, failrec->logical,
2129                                               failrec->len);
2130                 if (num_copies > 1)  {
2131                         repair_io_failure(inode, start, failrec->len,
2132                                           failrec->logical, page,
2133                                           pg_offset, failrec->failed_mirror);
2134                 }
2135         }

After separating all members to local varaibles, it points to ->len. Which is
used several times in code above.
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Qu Wenruo Feb. 23, 2016, 2:06 a.m. UTC | #2 
David Sterba wrote on 2016/02/22 18:58 +0100:
> On Thu, Feb 11, 2016 at 01:24:13PM +0100, David Sterba wrote:
>> We use the private member of extent_state to store the failrec and play
>> pointless pointer games.
>>
>> Signed-off-by: David Sterba <dsterba@suse.com>
>
> I'm not sure why, but my gcc 5.3.1 think's that a member of failrec can
> be used uninitialized:
>
>    CC [M]  fs/btrfs/extent_io.o
> fs/btrfs/extent_io.c: In function ‘clean_io_failure’:
> fs/btrfs/extent_io.c:2133:4: warning: ‘failrec’ may be used uninitialized in this function [-Wmaybe-uninitialized]
>      repair_io_failure(inode, start, failrec->len,
>      ^
>
After applying your patch on integration-4.6, and compiling, my gcc 
5.3.0 didn't give such warning though.

And I didn't see an official 5.3.1, but only 5.3 so I assume maybe it's 
related to the .1 from your distribution?
(As my gcc is from Archlinux, I assume minimally patched)

Thanks,
Qu

> which points to:
>
> 2126         if (state && state->start <= failrec->start &&
> 2127             state->end >= failrec->start + failrec->len - 1) {
> 2128                 num_copies = btrfs_num_copies(fs_info, failrec->logical,
> 2129                                               failrec->len);
> 2130                 if (num_copies > 1)  {
> 2131                         repair_io_failure(inode, start, failrec->len,
> 2132                                           failrec->logical, page,
> 2133                                           pg_offset, failrec->failed_mirror);
> 2134                 }
> 2135         }
>
> After separating all members to local varaibles, it points to ->len. Which is
> used several times in code above.
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
>


--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
David Sterba Feb. 23, 2016, 11:34 a.m. UTC | #3 
On Tue, Feb 23, 2016 at 10:06:59AM +0800, Qu Wenruo wrote:
> > I'm not sure why, but my gcc 5.3.1 think's that a member of failrec can
> > be used uninitialized:
> >
> >    CC [M]  fs/btrfs/extent_io.o
> > fs/btrfs/extent_io.c: In function ‘clean_io_failure’:
> > fs/btrfs/extent_io.c:2133:4: warning: ‘failrec’ may be used uninitialized in this function [-Wmaybe-uninitialized]
> >      repair_io_failure(inode, start, failrec->len,
> >      ^
> >
> After applying your patch on integration-4.6, and compiling, my gcc 
> 5.3.0 didn't give such warning though.
> 
> And I didn't see an official 5.3.1, but only 5.3 so I assume maybe it's 
> related to the .1 from your distribution?

Yes it's distro gcc 5.3 + patches. Arnd sent a patch to fix the warning.
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
diff mbox

Patch

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 2e7c97a3f344..f3910ac00d89 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -232,7 +232,7 @@  static struct extent_state *alloc_extent_state(gfp_t mask)
 	if (!state)
 		return state;
 	state->state = 0;
-	state->private = 0;
+	state->failrec = NULL;
 	RB_CLEAR_NODE(&state->rb_node);
 	btrfs_leak_debug_add(&state->leak_list, &states);
 	atomic_set(&state->refs, 1);
@@ -1844,7 +1844,8 @@  out:
  * set the private field for a given byte offset in the tree.  If there isn't
  * an extent_state there already, this does nothing.
  */
-static int set_state_private(struct extent_io_tree *tree, u64 start, u64 private)
+static int set_state_failrec(struct extent_io_tree *tree, u64 start,
+		struct io_failure_record *failrec)
 {
 	struct rb_node *node;
 	struct extent_state *state;
@@ -1865,13 +1866,14 @@  static int set_state_private(struct extent_io_tree *tree, u64 start, u64 private
 		ret = -ENOENT;
 		goto out;
 	}
-	state->private = private;
+	state->failrec = failrec;
 out:
 	spin_unlock(&tree->lock);
 	return ret;
 }
 
-int get_state_private(struct extent_io_tree *tree, u64 start, u64 *private)
+static int get_state_failrec(struct extent_io_tree *tree, u64 start,
+		struct io_failure_record **failrec)
 {
 	struct rb_node *node;
 	struct extent_state *state;
@@ -1892,7 +1894,7 @@  int get_state_private(struct extent_io_tree *tree, u64 start, u64 *private)
 		ret = -ENOENT;
 		goto out;
 	}
-	*private = state->private;
+	*failrec = state->failrec;
 out:
 	spin_unlock(&tree->lock);
 	return ret;
@@ -1972,7 +1974,7 @@  int free_io_failure(struct inode *inode, struct io_failure_record *rec)
 	int err = 0;
 	struct extent_io_tree *failure_tree = &BTRFS_I(inode)->io_failure_tree;
 
-	set_state_private(failure_tree, rec->start, 0);
+	set_state_failrec(failure_tree, rec->start, NULL);
 	ret = clear_extent_bits(failure_tree, rec->start,
 				rec->start + rec->len - 1,
 				EXTENT_LOCKED | EXTENT_DIRTY, GFP_NOFS);
@@ -2089,7 +2091,6 @@  int clean_io_failure(struct inode *inode, u64 start, struct page *page,
 		     unsigned int pg_offset)
 {
 	u64 private;
-	u64 private_failure;
 	struct io_failure_record *failrec;
 	struct btrfs_fs_info *fs_info = BTRFS_I(inode)->root->fs_info;
 	struct extent_state *state;
@@ -2102,12 +2103,11 @@  int clean_io_failure(struct inode *inode, u64 start, struct page *page,
 	if (!ret)
 		return 0;
 
-	ret = get_state_private(&BTRFS_I(inode)->io_failure_tree, start,
-				&private_failure);
+	ret = get_state_failrec(&BTRFS_I(inode)->io_failure_tree, start,
+			&failrec);
 	if (ret)
 		return 0;
 
-	failrec = (struct io_failure_record *)(unsigned long) private_failure;
 	BUG_ON(!failrec->this_mirror);
 
 	if (failrec->in_validation) {
@@ -2167,7 +2167,7 @@  void btrfs_free_io_failure_record(struct inode *inode, u64 start, u64 end)
 
 		next = next_state(state);
 
-		failrec = (struct io_failure_record *)(unsigned long)state->private;
+		failrec = state->failrec;
 		free_extent_state(state);
 		kfree(failrec);
 
@@ -2177,10 +2177,9 @@  void btrfs_free_io_failure_record(struct inode *inode, u64 start, u64 end)
 }
 
 int btrfs_get_io_failure_record(struct inode *inode, u64 start, u64 end,
-				struct io_failure_record **failrec_ret)
+		struct io_failure_record **failrec_ret)
 {
 	struct io_failure_record *failrec;
-	u64 private;
 	struct extent_map *em;
 	struct extent_io_tree *failure_tree = &BTRFS_I(inode)->io_failure_tree;
 	struct extent_io_tree *tree = &BTRFS_I(inode)->io_tree;
@@ -2188,7 +2187,7 @@  int btrfs_get_io_failure_record(struct inode *inode, u64 start, u64 end,
 	int ret;
 	u64 logical;
 
-	ret = get_state_private(failure_tree, start, &private);
+	ret = get_state_failrec(failure_tree, start, &failrec);
 	if (ret) {
 		failrec = kzalloc(sizeof(*failrec), GFP_NOFS);
 		if (!failrec)
@@ -2237,8 +2236,7 @@  int btrfs_get_io_failure_record(struct inode *inode, u64 start, u64 end,
 		ret = set_extent_bits(failure_tree, start, end,
 					EXTENT_LOCKED | EXTENT_DIRTY, GFP_NOFS);
 		if (ret >= 0)
-			ret = set_state_private(failure_tree, start,
-						(u64)(unsigned long)failrec);
+			ret = set_state_failrec(failure_tree, start, failrec);
 		/* set the bits in the inode's tree */
 		if (ret >= 0)
 			ret = set_extent_bits(tree, start, end, EXTENT_DAMAGED,
@@ -2248,7 +2246,6 @@  int btrfs_get_io_failure_record(struct inode *inode, u64 start, u64 end,
 			return ret;
 		}
 	} else {
-		failrec = (struct io_failure_record *)(unsigned long)private;
 		pr_debug("Get IO Failure Record: (found) logical=%llu, start=%llu, len=%llu, validation=%d\n",
 			 failrec->logical, failrec->start, failrec->len,
 			 failrec->in_validation);
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index 0377413bd4b9..98a25a100674 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -62,6 +62,7 @@ 
 struct extent_state;
 struct btrfs_root;
 struct btrfs_io_bio;
+struct io_failure_record;
 
 typedef	int (extent_submit_bio_hook_t)(struct inode *inode, int rw,
 				       struct bio *bio, int mirror_num,
@@ -112,8 +113,7 @@  struct extent_state {
 	atomic_t refs;
 	unsigned state;
 
-	/* for use by the FS */
-	u64 private;
+	struct io_failure_record *failrec;
 
 #ifdef CONFIG_BTRFS_DEBUG
 	struct list_head leak_list;
@@ -345,7 +345,6 @@  int extent_readpages(struct extent_io_tree *tree,
 		     get_extent_t get_extent);
 int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 		__u64 start, __u64 len, get_extent_t *get_extent);
-int get_state_private(struct extent_io_tree *tree, u64 start, u64 *private);
 void set_page_extent_mapped(struct page *page);
 
 struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,