Merge branch 'akpm' (second patchbomb from Andrew Morton)

Merge more incoming from Andrew Morton:
 "Two new syscalls:

     memfd_create in "shm: add memfd_create() syscall"
     kexec_file_load in "kexec: implementation of new syscall kexec_file_load"

  And:

   - Most (all?) of the rest of MM

   - Lots of the usual misc bits

   - fs/autofs4

   - drivers/rtc

   - fs/nilfs

   - procfs

   - fork.c, exec.c

   - more in lib/

   - rapidio

   - Janitorial work in filesystems: fs/ufs, fs/reiserfs, fs/adfs,
     fs/cramfs, fs/romfs, fs/qnx6.

   - initrd/initramfs work

   - "file sealing" and the memfd_create() syscall, in tmpfs

   - add pci_zalloc_consistent, use it in lots of places

   - MAINTAINERS maintenance

   - kexec feature work"

* emailed patches from Andrew Morton <akpm@linux-foundation.org: (193 commits)
  MAINTAINERS: update nomadik patterns
  MAINTAINERS: update usb/gadget patterns
  MAINTAINERS: update DMA BUFFER SHARING patterns
  kexec: verify the signature of signed PE bzImage
  kexec: support kexec/kdump on EFI systems
  kexec: support for kexec on panic using new system call
  kexec-bzImage64: support for loading bzImage using 64bit entry
  kexec: load and relocate purgatory at kernel load time
  purgatory: core purgatory functionality
  purgatory/sha256: provide implementation of sha256 in purgaotory context
  kexec: implementation of new syscall kexec_file_load
  kexec: new syscall kexec_file_load() declaration
  kexec: make kexec_segment user buffer pointer a union
  resource: provide new functions to walk through resources
  kexec: use common function for kimage_normal_alloc() and kimage_crash_alloc()
  kexec: move segment verification code in a separate function
  kexec: rename unusebale_pages to unusable_pages
  kernel: build bin2c based on config option CONFIG_BUILD_BIN2C
  bin2c: move bin2c in scripts/basic
  shm: wait for pins to be released when sealing
  ...

1 files changed, 27 insertions, 2 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 1ab6c6913040..f0890e4a7c25 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -387,7 +387,7 @@ struct address_space {
 	struct inode		*host;		/* owner: inode, block_device */
 	struct radix_tree_root	page_tree;	/* radix tree of all pages */
 	spinlock_t		tree_lock;	/* and lock protecting it */
-	unsigned int		i_mmap_writable;/* count VM_SHARED mappings */
+	atomic_t		i_mmap_writable;/* count VM_SHARED mappings */
 	struct rb_root		i_mmap;		/* tree of private and shared mappings */
 	struct list_head	i_mmap_nonlinear;/*list VM_NONLINEAR mappings */
 	struct mutex		i_mmap_mutex;	/* protect tree, count, list */
@@ -470,10 +470,35 @@ static inline int mapping_mapped(struct address_space *mapping)
  * Note that i_mmap_writable counts all VM_SHARED vmas: do_mmap_pgoff
  * marks vma as VM_SHARED if it is shared, and the file was opened for
  * writing i.e. vma may be mprotected writable even if now readonly.
+ *
+ * If i_mmap_writable is negative, no new writable mappings are allowed. You
+ * can only deny writable mappings, if none exists right now.
  */
 static inline int mapping_writably_mapped(struct address_space *mapping)
 {
-	return mapping->i_mmap_writable != 0;
+	return atomic_read(&mapping->i_mmap_writable) > 0;
+}
+
+static inline int mapping_map_writable(struct address_space *mapping)
+{
+	return atomic_inc_unless_negative(&mapping->i_mmap_writable) ?
+		0 : -EPERM;
+}
+
+static inline void mapping_unmap_writable(struct address_space *mapping)
+{
+	atomic_dec(&mapping->i_mmap_writable);
+}
+
+static inline int mapping_deny_writable(struct address_space *mapping)
+{
+	return atomic_dec_unless_positive(&mapping->i_mmap_writable) ?
+		0 : -EBUSY;
+}
+
+static inline void mapping_allow_writable(struct address_space *mapping)
+{
+	atomic_inc(&mapping->i_mmap_writable);
 }
 
 /*