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Btrfs: use rcu to protect device->name

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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>
This commit is contained in:
Josef Bacik
2012-06-04 14:03:51 -04:00
committed by Chris Mason
parent 17ca04aff7
commit 606686eeac
8 changed files with 162 additions and 64 deletions
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7
fs/btrfs/extent_io.c
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@@ -20,6 +20,7 @@
#include "volumes.h"
#include "check-integrity.h"
#include "locking.h"
#include "rcu-string.h"
static struct kmem_cache *extent_state_cache;
static struct kmem_cache *extent_buffer_cache;
@@ -1917,9 +1918,9 @@ int repair_io_failure(struct btrfs_mapping_tree *map_tree, u64 start,
return -EIO;
}
printk(KERN_INFO "btrfs read error corrected: ino %lu off %llu (dev %s "
"sector %llu)\n", page->mapping->host->i_ino, start,
dev->name, sector);
printk_in_rcu(KERN_INFO "btrfs read error corrected: ino %lu off %llu "
"(dev %s sector %llu)\n", page->mapping->host->i_ino,
start, rcu_str_deref(dev->name), sector);
bio_put(bio);
return 0;