Attachment 146716 Details for Bug 190611 – Patch to eliminate the i_mapping race in bd_acquire().

[patch] Patch to eliminate the i_mapping race in bd_acquire().

01_imapping_race.patch (text/plain), 1.53 KB, created by Bob Miller on 2007-01-26 21:30:52 UTC

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Creator: Bob Miller

Created: 2007-01-26 21:30:52 UTC

Size: 1.53 KB

patch

obsolete

>--- linux-2.6.9-42.EL.orig/fs/block_dev.c	2006-11-17 09:56:50.000000000 -0800
>+++ linux-2.6.9-42.EL/fs/block_dev.c	2006-11-17 10:03:59.000000000 -0800
>@@ -413,21 +413,31 @@
> static struct block_device *bd_acquire(struct inode *inode)
> {
> 	struct block_device *bdev;
>+
> 	spin_lock(&bdev_lock);
> 	bdev = inode->i_bdev;
>-	if (bdev && igrab(bdev->bd_inode)) {
>+	if (bdev) {
>+		atomic_inc(&bdev->bd_inode->i_count);
> 		spin_unlock(&bdev_lock);
> 		return bdev;
> 	}
> 	spin_unlock(&bdev_lock);
>+
> 	bdev = bdget(inode->i_rdev);
> 	if (bdev) {
> 		spin_lock(&bdev_lock);
>-		if (inode->i_bdev)
>-			__bd_forget(inode);
>-		inode->i_bdev = bdev;
>-		inode->i_mapping = bdev->bd_inode->i_mapping;
>-		list_add(&inode->i_devices, &bdev->bd_inodes);
>+		if (!inode->i_bdev) {
>+			/*
>+			 * We take an additional bd_inode->i_count for inode,
>+			 * and it's released in clear_inode() of inode.
>+			 * So, we can access it via ->i_mapping always
>+			 * without igrab().
>+			 */
>+			atomic_inc(&bdev->bd_inode->i_count);
>+			inode->i_bdev = bdev;
>+			inode->i_mapping = bdev->bd_inode->i_mapping;
>+			list_add(&inode->i_devices, &bdev->bd_inodes);
>+		}
> 		spin_unlock(&bdev_lock);
> 	}
> 	return bdev;
>@@ -437,10 +447,18 @@
> 
> void bd_forget(struct inode *inode)
> {
>+	struct block_device *bdev = NULL;
>+
> 	spin_lock(&bdev_lock);
>-	if (inode->i_bdev)
>+	if (inode->i_bdev) {
>+		if (inode->i_sb != blockdev_superblock)
>+			bdev = inode->i_bdev;
> 		__bd_forget(inode);
>+	}
> 	spin_unlock(&bdev_lock);
>+
>+	if (bdev)
>+		iput(bdev->bd_inode);
> }
> 
> int bd_claim(struct block_device *bdev, void *holder)

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Attachments on bug 190611: 146716