mm: prevent concurrent unmap_mapping_range() on the same inode

commit 2aa15890f3c191326678f1bd68af61ec6b8753ec upstream.

Michael Leun reported that running parallel opens on a fuse filesystem
can trigger a "kernel BUG at mm/truncate.c:475"

Gurudas Pai reported the same bug on NFS.

The reason is, unmap_mapping_range() is not prepared for more than
one concurrent invocation per inode.  For example:

  thread1: going through a big range, stops in the middle of a vma and
     stores the restart address in vm_truncate_count.

  thread2: comes in with a small (e.g. single page) unmap request on
     the same vma, somewhere before restart_address, finds that the
     vma was already unmapped up to the restart address and happily
     returns without doing anything.

Another scenario would be two big unmap requests, both having to
restart the unmapping and each one setting vm_truncate_count to its
own value.  This could go on forever without any of them being able to
finish.

Truncate and hole punching already serialize with i_mutex.  Other
callers of unmap_mapping_range() do not, and it's difficult to get
i_mutex protection for all callers.  In particular ->d_revalidate(),
which calls invalidate_inode_pages2_range() in fuse, may be called
with or without i_mutex.

This patch adds a new mutex to 'struct address_space' to prevent
running multiple concurrent unmap_mapping_range() on the same mapping.

[ We'll hopefully get rid of all this with the upcoming mm
  preemptibility series by Peter Zijlstra, the "mm: Remove i_mmap_mutex
  lockbreak" patch in particular.  But that is for 2.6.39 ]

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Reported-by: Michael Leun <lkml20101129@newton.leun.net>
Reported-by: Gurudas Pai <gurudas.pai@oracle.com>
Tested-by: Gurudas Pai <gurudas.pai@oracle.com>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/fs/inode.c b/fs/inode.c
index 4d8e3be55976272732f6f42610ab7813f66b8133..8bbe00541e7fe4ee2cfcad1774a5099437270998 100644 (file)
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -256,6 +256,20 @@ void destroy_inode(struct inode *inode)
                kmem_cache_free(inode_cachep, (inode));
 }
 
+void address_space_init_once(struct address_space *mapping)
+{
+       memset(mapping, 0, sizeof(*mapping));
+       INIT_RADIX_TREE(&mapping->page_tree, GFP_ATOMIC);
+       spin_lock_init(&mapping->tree_lock);
+       spin_lock_init(&mapping->i_mmap_lock);
+       INIT_LIST_HEAD(&mapping->private_list);
+       spin_lock_init(&mapping->private_lock);
+       INIT_RAW_PRIO_TREE_ROOT(&mapping->i_mmap);
+       INIT_LIST_HEAD(&mapping->i_mmap_nonlinear);
+       mutex_init(&mapping->unmap_mutex);
+}
+EXPORT_SYMBOL(address_space_init_once);
+
 /*
  * These are initializations that only need to be done
  * once, because the fields are idempotent across use
@@ -267,13 +281,7 @@ void inode_init_once(struct inode *inode)
        INIT_HLIST_NODE(&inode->i_hash);
        INIT_LIST_HEAD(&inode->i_dentry);
        INIT_LIST_HEAD(&inode->i_devices);
-       INIT_RADIX_TREE(&inode->i_data.page_tree, GFP_ATOMIC);
-       spin_lock_init(&inode->i_data.tree_lock);
-       spin_lock_init(&inode->i_data.i_mmap_lock);
-       INIT_LIST_HEAD(&inode->i_data.private_list);
-       spin_lock_init(&inode->i_data.private_lock);
-       INIT_RAW_PRIO_TREE_ROOT(&inode->i_data.i_mmap);
-       INIT_LIST_HEAD(&inode->i_data.i_mmap_nonlinear);
+       address_space_init_once(&inode->i_data);
        i_size_ordered_init(inode);
 #ifdef CONFIG_INOTIFY
        INIT_LIST_HEAD(&inode->inotify_watches);

diff --git a/fs/nilfs2/btnode.c b/fs/nilfs2/btnode.c
index 84c25382f8e3b35b13f6509463aef70308bb3164..8dff3176111b4c1a077d977aae395eb12cec8f8f 100644 (file)
--- a/fs/nilfs2/btnode.c
+++ b/fs/nilfs2/btnode.c
@@ -34,19 +34,6 @@
 #include "btnode.h"
 
 
-void nilfs_btnode_cache_init_once(struct address_space *btnc)
-{
-       memset(btnc, 0, sizeof(*btnc));
-       INIT_RADIX_TREE(&btnc->page_tree, GFP_ATOMIC);
-       spin_lock_init(&btnc->tree_lock);
-       INIT_LIST_HEAD(&btnc->private_list);
-       spin_lock_init(&btnc->private_lock);
-
-       spin_lock_init(&btnc->i_mmap_lock);
-       INIT_RAW_PRIO_TREE_ROOT(&btnc->i_mmap);
-       INIT_LIST_HEAD(&btnc->i_mmap_nonlinear);
-}
-
 static const struct address_space_operations def_btnode_aops = {
        .sync_page              = block_sync_page,
 };

diff --git a/fs/nilfs2/btnode.h b/fs/nilfs2/btnode.h
index 3e2275172ed623cc48e428619fdd66b9a47484a9..067913ea2b0ea7901228687a9f47f27a1a827f64 100644 (file)
--- a/fs/nilfs2/btnode.h
+++ b/fs/nilfs2/btnode.h
@@ -37,7 +37,6 @@ struct nilfs_btnode_chkey_ctxt {
        struct buffer_head *newbh;
 };
 
-void nilfs_btnode_cache_init_once(struct address_space *);
 void nilfs_btnode_cache_init(struct address_space *, struct backing_dev_info *);
 void nilfs_btnode_cache_clear(struct address_space *);
 int nilfs_btnode_submit_block(struct address_space *, __u64, sector_t,

diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
index 63e7b108ff8353c7e9dc7817aea5f89fe78d9560..93c11af3562aa51308a587b642c2b2447cabe2dc 100644 (file)
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -166,7 +166,7 @@ static void init_once(void *obj)
 #ifdef CONFIG_NILFS_XATTR
        init_rwsem(&ii->xattr_sem);
 #endif
-       nilfs_btnode_cache_init_once(&ii->i_btnode_cache);
+       address_space_init_once(&ii->i_btnode_cache);
        ii->i_bmap = (struct nilfs_bmap *)&ii->i_bmap_union;
        inode_init_once(&ii->vfs_inode);
 }

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 1ff096263b59f7f76bb9c6452f4c50209e9e3462..1b9a47abb0149b6c5e139812a1df89cec088e0a4 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -635,6 +635,7 @@ struct address_space {
        spinlock_t              private_lock;   /* for use by the address_space */
        struct list_head        private_list;   /* ditto */
        struct address_space    *assoc_mapping; /* ditto */
+       struct mutex            unmap_mutex;    /* to protect unmapping */
 } __attribute__((aligned(sizeof(long))));
        /*
         * On most architectures that alignment is already the case; but
@@ -2158,6 +2159,7 @@ extern loff_t vfs_llseek(struct file *file, loff_t offset, int origin);
 
 extern int inode_init_always(struct super_block *, struct inode *);
 extern void inode_init_once(struct inode *);
+extern void address_space_init_once(struct address_space *mapping);
 extern void inode_add_to_lists(struct super_block *, struct inode *);
 extern void iput(struct inode *);
 extern struct inode * igrab(struct inode *);

diff --git a/mm/memory.c b/mm/memory.c
index 53c1da0d04a68d02bd1fd9eba8c925ceda59fec8..6c836d36f2f0ab3a0979c1bf978f060f457ab9b5 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2454,6 +2454,7 @@ void unmap_mapping_range(struct address_space *mapping,
                details.last_index = ULONG_MAX;
        details.i_mmap_lock = &mapping->i_mmap_lock;
 
+       mutex_lock(&mapping->unmap_mutex);
        spin_lock(&mapping->i_mmap_lock);
 
        /* Protect against endless unmapping loops */
@@ -2470,6 +2471,7 @@ void unmap_mapping_range(struct address_space *mapping,
        if (unlikely(!list_empty(&mapping->i_mmap_nonlinear)))
                unmap_mapping_range_list(&mapping->i_mmap_nonlinear, &details);
        spin_unlock(&mapping->i_mmap_lock);
+       mutex_unlock(&mapping->unmap_mutex);
 }
 EXPORT_SYMBOL(unmap_mapping_range);