Btrfs: use rcu to protect device->name
Al pointed out that we can just toss out the old name on a device and add a
new one arbitrarily, so anybody who uses device->name in printk could
possibly use free'd memory. Instead of adding locking around all of this he
suggested doing it with RCU, so I've introduced a struct rcu_string that
does just that and have gone through and protected all accesses to
device->name that aren't under the uuid_mutex with rcu_read_lock(). This
protects us and I will use it for dealing with removing the device that we
used to mount the file system in a later patch. Thanks,
Reviewed-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Josef Bacik <josef@redhat.com>
diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index a38cfa4..b223620 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -26,6 +26,7 @@
#include "backref.h"
#include "extent_io.h"
#include "check-integrity.h"
+#include "rcu-string.h"
/*
* This is only the first step towards a full-features scrub. It reads all
@@ -320,10 +321,10 @@
* hold all of the paths here
*/
for (i = 0; i < ipath->fspath->elem_cnt; ++i)
- printk(KERN_WARNING "btrfs: %s at logical %llu on dev "
+ printk_in_rcu(KERN_WARNING "btrfs: %s at logical %llu on dev "
"%s, sector %llu, root %llu, inode %llu, offset %llu, "
"length %llu, links %u (path: %s)\n", swarn->errstr,
- swarn->logical, swarn->dev->name,
+ swarn->logical, rcu_str_deref(swarn->dev->name),
(unsigned long long)swarn->sector, root, inum, offset,
min(isize - offset, (u64)PAGE_SIZE), nlink,
(char *)(unsigned long)ipath->fspath->val[i]);
@@ -332,10 +333,10 @@
return 0;
err:
- printk(KERN_WARNING "btrfs: %s at logical %llu on dev "
+ printk_in_rcu(KERN_WARNING "btrfs: %s at logical %llu on dev "
"%s, sector %llu, root %llu, inode %llu, offset %llu: path "
"resolving failed with ret=%d\n", swarn->errstr,
- swarn->logical, swarn->dev->name,
+ swarn->logical, rcu_str_deref(swarn->dev->name),
(unsigned long long)swarn->sector, root, inum, offset, ret);
free_ipath(ipath);
@@ -390,10 +391,11 @@
do {
ret = tree_backref_for_extent(&ptr, eb, ei, item_size,
&ref_root, &ref_level);
- printk(KERN_WARNING
+ printk_in_rcu(KERN_WARNING
"btrfs: %s at logical %llu on dev %s, "
"sector %llu: metadata %s (level %d) in tree "
- "%llu\n", errstr, swarn.logical, dev->name,
+ "%llu\n", errstr, swarn.logical,
+ rcu_str_deref(dev->name),
(unsigned long long)swarn.sector,
ref_level ? "node" : "leaf",
ret < 0 ? -1 : ref_level,
@@ -580,9 +582,11 @@
spin_lock(&sdev->stat_lock);
++sdev->stat.uncorrectable_errors;
spin_unlock(&sdev->stat_lock);
- printk_ratelimited(KERN_ERR
+
+ printk_ratelimited_in_rcu(KERN_ERR
"btrfs: unable to fixup (nodatasum) error at logical %llu on dev %s\n",
- (unsigned long long)fixup->logical, sdev->dev->name);
+ (unsigned long long)fixup->logical,
+ rcu_str_deref(sdev->dev->name));
}
btrfs_free_path(path);
@@ -936,18 +940,20 @@
spin_lock(&sdev->stat_lock);
sdev->stat.corrected_errors++;
spin_unlock(&sdev->stat_lock);
- printk_ratelimited(KERN_ERR
+ printk_ratelimited_in_rcu(KERN_ERR
"btrfs: fixed up error at logical %llu on dev %s\n",
- (unsigned long long)logical, sdev->dev->name);
+ (unsigned long long)logical,
+ rcu_str_deref(sdev->dev->name));
}
} else {
did_not_correct_error:
spin_lock(&sdev->stat_lock);
sdev->stat.uncorrectable_errors++;
spin_unlock(&sdev->stat_lock);
- printk_ratelimited(KERN_ERR
+ printk_ratelimited_in_rcu(KERN_ERR
"btrfs: unable to fixup (regular) error at logical %llu on dev %s\n",
- (unsigned long long)logical, sdev->dev->name);
+ (unsigned long long)logical,
+ rcu_str_deref(sdev->dev->name));
}
out:
