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>
[PG: Some chunks dropped, since no ebdfed4dc5 in 34; came in at 2.6.37]
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/fs/gfs2/main.c b/fs/gfs2/main.c
index a88fadc704bb228b82f179c356625ab4af4a12f9..79ebf86454d3b84fd505517b6a6f2944d8659ddf 100644 (file)
--- a/fs/gfs2/main.c
+++ b/fs/gfs2/main.c
@@ -58,14 +58,7 @@ static void gfs2_init_gl_aspace_once(void *foo)
        struct address_space *mapping = (struct address_space *)(gl + 1);
 
        gfs2_init_glock_once(gl);
-       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);
+       address_space_init_once(mapping);
 }
 
 /**

diff --git a/fs/inode.c b/fs/inode.c
index 407bf392e20a67e9494537258ffe2ad73b92a8cb..f84377a0b8c53eba4981e3540dd63d543dd1b2ef 100644 (file)
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -245,6 +245,20 @@ 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
@@ -256,13 +270,7 @@ 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 447ce47a3306f6635a0512a8e25580ae93c0620b..bebb9a97254c6322a13fd319bb945b01bb33d69f 100644 (file)
--- a/fs/nilfs2/btnode.c
+++ b/fs/nilfs2/btnode.c
@@ -34,20 +34,6 @@
 #include "page.h"
 #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 07da83f07712a9caa7afd6a673bc070783d20795..fa2f1e68f4d17f3d720ecb0a0b5818915712ddc0 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 *);
 struct buffer_head *nilfs_btnode_create_block(struct address_space *btnc,

diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
index fadefe1214c27b636e089e7c4773fd6f17fe037c..bce4109659812856db599f392298c8171312ffce 100644 (file)
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -163,7 +163,7 @@ 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 8aa6bd9ddc0977e88c26477c290767c571136cd4..2e97c2ca4949d8c292be2149c5f43a397498d84f 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -638,6 +638,7 @@ 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
@@ -2145,6 +2146,7 @@ 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 3410236330b63c77419c61fcb3b433a4bf9cca35..43dc21683079d732bb48f83224fe1309045444bb 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2564,6 +2564,7 @@ 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 */
@@ -2580,6 +2581,7 @@ 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);