diff mbox

[3/4] cifs: fix potential races in cifs_revalidate_mapping

Message ID 1396288209-27328-4-git-send-email-jlayton@redhat.com (mailing list archive)
State New, archived
Headers show

Commit Message

Jeff Layton March 31, 2014, 5:50 p.m. UTC
The handling of the CIFS_INO_INVALID_MAPPING flag is racy. It's possible
for two tasks to attempt to revalidate the mapping at the same time. The
first sees that CIFS_INO_INVALID_MAPPING is set. It clears the flag and
then calls invalidate_inode_pages2 to start shooting down the pagecache.

While that's going on, another task checks the flag and sees that it's
clear. It then ends up trusting the pagecache to satisfy a read when it
shouldn't.

Fix this by adding a bitlock to ensure that the clearing of the flag is
atomic with respect to the actual cache invalidation. Also, move the
other existing users of cifs_invalidate_mapping to use a new
cifs_zap_mapping() function that just sets the INVALID_MAPPING bit and
then uses the standard codepath to handle the invalidation.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
---
 fs/cifs/cifsfs.h   |  1 +
 fs/cifs/cifsglob.h |  1 +
 fs/cifs/file.c     | 12 ++++++------
 fs/cifs/inode.c    | 50 +++++++++++++++++++++++++++++++++++++++++---------
 4 files changed, 49 insertions(+), 15 deletions(-)

Comments

Steve French April 25, 2014, 3:48 a.m. UTC | #1
Various minor whitespace errors on this - do you want to respin it or
want me to fix it up?

On Mon, Mar 31, 2014 at 12:50 PM, Jeff Layton <jlayton@redhat.com> wrote:
> The handling of the CIFS_INO_INVALID_MAPPING flag is racy. It's possible
> for two tasks to attempt to revalidate the mapping at the same time. The
> first sees that CIFS_INO_INVALID_MAPPING is set. It clears the flag and
> then calls invalidate_inode_pages2 to start shooting down the pagecache.
>
> While that's going on, another task checks the flag and sees that it's
> clear. It then ends up trusting the pagecache to satisfy a read when it
> shouldn't.
>
> Fix this by adding a bitlock to ensure that the clearing of the flag is
> atomic with respect to the actual cache invalidation. Also, move the
> other existing users of cifs_invalidate_mapping to use a new
> cifs_zap_mapping() function that just sets the INVALID_MAPPING bit and
> then uses the standard codepath to handle the invalidation.
>
> Signed-off-by: Jeff Layton <jlayton@redhat.com>
> ---
>  fs/cifs/cifsfs.h   |  1 +
>  fs/cifs/cifsglob.h |  1 +
>  fs/cifs/file.c     | 12 ++++++------
>  fs/cifs/inode.c    | 50 +++++++++++++++++++++++++++++++++++++++++---------
>  4 files changed, 49 insertions(+), 15 deletions(-)
>
> diff --git a/fs/cifs/cifsfs.h b/fs/cifs/cifsfs.h
> index 40d5a4df1e38..b7cf9ee7654b 100644
> --- a/fs/cifs/cifsfs.h
> +++ b/fs/cifs/cifsfs.h
> @@ -68,6 +68,7 @@ extern int cifs_revalidate_file(struct file *filp);
>  extern int cifs_revalidate_dentry(struct dentry *);
>  extern int cifs_invalidate_mapping(struct inode *inode);
>  extern int cifs_revalidate_mapping(struct inode *inode);
> +extern int cifs_zap_mapping(struct inode *inode);
>  extern int cifs_getattr(struct vfsmount *, struct dentry *, struct kstat *);
>  extern int cifs_setattr(struct dentry *, struct iattr *);
>
> diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
> index 0d4a1039ac27..84cd4447cc31 100644
> --- a/fs/cifs/cifsglob.h
> +++ b/fs/cifs/cifsglob.h
> @@ -1111,6 +1111,7 @@ struct cifsInodeInfo {
>         __u32 cifsAttrs; /* e.g. DOS archive bit, sparse, compressed, system */
>         unsigned int oplock;            /* oplock/lease level we have */
>         unsigned int epoch;             /* used to track lease state changes */
> +#define CIFS_INO_LOCK                  (0)
>  #define CIFS_INO_DELETE_PENDING                (1)
>  #define CIFS_INO_INVALID_MAPPING       (2)
>         unsigned long flags;            /* flags field */
> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> index 784b17d510fc..ccca61803f0a 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -335,7 +335,7 @@ cifs_new_fileinfo(struct cifs_fid *fid, struct file *file,
>         spin_unlock(&cifs_file_list_lock);
>
>         if (fid->purge_cache)
> -               cifs_invalidate_mapping(inode);
> +               cifs_zap_mapping(inode);
>
>         file->private_data = cfile;
>         return cfile;
> @@ -1529,7 +1529,7 @@ cifs_setlk(struct file *file, struct file_lock *flock, __u32 type,
>                  */
>                 if (!CIFS_CACHE_WRITE(CIFS_I(inode)) &&
>                                         CIFS_CACHE_READ(CIFS_I(inode))) {
> -                       cifs_invalidate_mapping(inode);
> +                       cifs_zap_mapping(inode);
>                         cifs_dbg(FYI, "Set no oplock for inode=%p due to mand locks\n",
>                                  inode);
>                         CIFS_I(inode)->oplock = 0;
> @@ -2218,7 +2218,7 @@ int cifs_strict_fsync(struct file *file, loff_t start, loff_t end,
>                  file->f_path.dentry->d_name.name, datasync);
>
>         if (!CIFS_CACHE_READ(CIFS_I(inode))) {
> -               rc = cifs_invalidate_mapping(inode);
> +               rc = cifs_zap_mapping(inode);
>                 if (rc) {
>                         cifs_dbg(FYI, "rc: %d during invalidate phase\n", rc);
>                         rc = 0; /* don't care about it in fsync */
> @@ -2628,7 +2628,7 @@ cifs_strict_writev(struct kiocb *iocb, const struct iovec *iov,
>                  * request comes - break it on the client to prevent reading
>                  * an old data.
>                  */
> -               cifs_invalidate_mapping(inode);
> +               cifs_zap_mapping(inode);
>                 cifs_dbg(FYI, "Set no oplock for inode=%p after a write operation\n",
>                          inode);
>                 cinode->oplock = 0;
> @@ -3125,7 +3125,7 @@ int cifs_file_strict_mmap(struct file *file, struct vm_area_struct *vma)
>         xid = get_xid();
>
>         if (!CIFS_CACHE_READ(CIFS_I(inode))) {
> -               rc = cifs_invalidate_mapping(inode);
> +               rc = cifs_zap_mapping(inode);
>                 if (rc)
>                         return rc;
>         }
> @@ -3669,7 +3669,7 @@ void cifs_oplock_break(struct work_struct *work)
>                 if (!CIFS_CACHE_READ(cinode)) {
>                         rc = filemap_fdatawait(inode->i_mapping);
>                         mapping_set_error(inode->i_mapping, rc);
> -                       cifs_invalidate_mapping(inode);
> +                       cifs_zap_mapping(inode);
>                 }
>                 cifs_dbg(FYI, "Oplock flush inode %p rc %d\n", inode, rc);
>         }
> diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
> index 39b76bac196d..b840930f6271 100644
> --- a/fs/cifs/inode.c
> +++ b/fs/cifs/inode.c
> @@ -22,6 +22,7 @@
>  #include <linux/stat.h>
>  #include <linux/slab.h>
>  #include <linux/pagemap.h>
> +#include <linux/freezer.h>
>  #include <asm/div64.h>
>  #include "cifsfs.h"
>  #include "cifspdu.h"
> @@ -1762,29 +1763,60 @@ int
>  cifs_invalidate_mapping(struct inode *inode)
>  {
>         int rc = 0;
> -       struct cifsInodeInfo *cifs_i = CIFS_I(inode);
> -
> -       clear_bit(CIFS_INO_INVALID_MAPPING, &cifs_i->flags);
>
>         if (inode->i_mapping && inode->i_mapping->nrpages != 0) {
>                 rc = invalidate_inode_pages2(inode->i_mapping);
> -               if (rc) {
> +               if (rc)
>                         cifs_dbg(VFS, "%s: could not invalidate inode %p\n",
>                                  __func__, inode);
> -                       set_bit(CIFS_INO_INVALID_MAPPING, &cifs_i->flags);
> -               }
>         }
>
>         cifs_fscache_reset_inode_cookie(inode);
>         return rc;
>  }
>
> +/**
> + * cifs_wait_bit_killable - helper for functions that are sleeping on bit locks
> + * @word: long word containing the bit lock
> + */
> +static int
> +cifs_wait_bit_killable(void *word)
> +{
> +       if (fatal_signal_pending(current))
> +               return -ERESTARTSYS;
> +       freezable_schedule_unsafe();
> +       return 0;
> +}
> +
>  int
>  cifs_revalidate_mapping(struct inode *inode)
>  {
> -       if (test_bit(CIFS_INODE_INVALID_MAPPING, &CIFS_I(inode)->flags));
> -               return cifs_invalidate_mapping(inode);
> -       return 0;
> +       int rc;
> +       unsigned long *flags = &CIFS_I(inode)->flags;
> +
> +       rc = wait_on_bit_lock(flags, CIFS_INO_LOCK, cifs_wait_bit_killable,
> +                               TASK_KILLABLE);
> +       if (rc)
> +               return rc;
> +
> +       if (test_and_clear_bit(CIFS_INO_INVALID_MAPPING, flags)) {
> +               rc = cifs_invalidate_mapping(inode);
> +               if (rc)
> +                       set_bit(CIFS_INO_INVALID_MAPPING, flags);
> +       }
> +
> +        clear_bit_unlock(CIFS_INO_LOCK, flags);
> +        smp_mb__after_clear_bit();
> +        wake_up_bit(flags, CIFS_INO_LOCK);
> +
> +       return rc;
> +}
> +
> +int
> +cifs_zap_mapping(struct inode *inode)
> +{
> +       set_bit(CIFS_INO_INVALID_MAPPING, &CIFS_I(inode)->flags);
> +       return cifs_revalidate_mapping(inode);
>  }
>
>  int cifs_revalidate_file_attr(struct file *filp)
> --
> 1.9.0
>
Jeff Layton April 25, 2014, 11:05 a.m. UTC | #2
On Thu, 24 Apr 2014 22:48:47 -0500
Steve French <smfrench@gmail.com> wrote:

> Various minor whitespace errors on this - do you want to respin it or
> want me to fix it up?
> 

I'll respin and resend the whole set. It needs some merge help anyway
to account for some of Sachin's changes. It'll probably be a few days
before I can get to it though. Probably best that we punt this set out
to v3.16.

Thanks,
Jeff


> On Mon, Mar 31, 2014 at 12:50 PM, Jeff Layton <jlayton@redhat.com> wrote:
> > The handling of the CIFS_INO_INVALID_MAPPING flag is racy. It's possible
> > for two tasks to attempt to revalidate the mapping at the same time. The
> > first sees that CIFS_INO_INVALID_MAPPING is set. It clears the flag and
> > then calls invalidate_inode_pages2 to start shooting down the pagecache.
> >
> > While that's going on, another task checks the flag and sees that it's
> > clear. It then ends up trusting the pagecache to satisfy a read when it
> > shouldn't.
> >
> > Fix this by adding a bitlock to ensure that the clearing of the flag is
> > atomic with respect to the actual cache invalidation. Also, move the
> > other existing users of cifs_invalidate_mapping to use a new
> > cifs_zap_mapping() function that just sets the INVALID_MAPPING bit and
> > then uses the standard codepath to handle the invalidation.
> >
> > Signed-off-by: Jeff Layton <jlayton@redhat.com>
> > ---
> >  fs/cifs/cifsfs.h   |  1 +
> >  fs/cifs/cifsglob.h |  1 +
> >  fs/cifs/file.c     | 12 ++++++------
> >  fs/cifs/inode.c    | 50 +++++++++++++++++++++++++++++++++++++++++---------
> >  4 files changed, 49 insertions(+), 15 deletions(-)
> >
> > diff --git a/fs/cifs/cifsfs.h b/fs/cifs/cifsfs.h
> > index 40d5a4df1e38..b7cf9ee7654b 100644
> > --- a/fs/cifs/cifsfs.h
> > +++ b/fs/cifs/cifsfs.h
> > @@ -68,6 +68,7 @@ extern int cifs_revalidate_file(struct file *filp);
> >  extern int cifs_revalidate_dentry(struct dentry *);
> >  extern int cifs_invalidate_mapping(struct inode *inode);
> >  extern int cifs_revalidate_mapping(struct inode *inode);
> > +extern int cifs_zap_mapping(struct inode *inode);
> >  extern int cifs_getattr(struct vfsmount *, struct dentry *, struct kstat *);
> >  extern int cifs_setattr(struct dentry *, struct iattr *);
> >
> > diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
> > index 0d4a1039ac27..84cd4447cc31 100644
> > --- a/fs/cifs/cifsglob.h
> > +++ b/fs/cifs/cifsglob.h
> > @@ -1111,6 +1111,7 @@ struct cifsInodeInfo {
> >         __u32 cifsAttrs; /* e.g. DOS archive bit, sparse, compressed, system */
> >         unsigned int oplock;            /* oplock/lease level we have */
> >         unsigned int epoch;             /* used to track lease state changes */
> > +#define CIFS_INO_LOCK                  (0)
> >  #define CIFS_INO_DELETE_PENDING                (1)
> >  #define CIFS_INO_INVALID_MAPPING       (2)
> >         unsigned long flags;            /* flags field */
> > diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> > index 784b17d510fc..ccca61803f0a 100644
> > --- a/fs/cifs/file.c
> > +++ b/fs/cifs/file.c
> > @@ -335,7 +335,7 @@ cifs_new_fileinfo(struct cifs_fid *fid, struct file *file,
> >         spin_unlock(&cifs_file_list_lock);
> >
> >         if (fid->purge_cache)
> > -               cifs_invalidate_mapping(inode);
> > +               cifs_zap_mapping(inode);
> >
> >         file->private_data = cfile;
> >         return cfile;
> > @@ -1529,7 +1529,7 @@ cifs_setlk(struct file *file, struct file_lock *flock, __u32 type,
> >                  */
> >                 if (!CIFS_CACHE_WRITE(CIFS_I(inode)) &&
> >                                         CIFS_CACHE_READ(CIFS_I(inode))) {
> > -                       cifs_invalidate_mapping(inode);
> > +                       cifs_zap_mapping(inode);
> >                         cifs_dbg(FYI, "Set no oplock for inode=%p due to mand locks\n",
> >                                  inode);
> >                         CIFS_I(inode)->oplock = 0;
> > @@ -2218,7 +2218,7 @@ int cifs_strict_fsync(struct file *file, loff_t start, loff_t end,
> >                  file->f_path.dentry->d_name.name, datasync);
> >
> >         if (!CIFS_CACHE_READ(CIFS_I(inode))) {
> > -               rc = cifs_invalidate_mapping(inode);
> > +               rc = cifs_zap_mapping(inode);
> >                 if (rc) {
> >                         cifs_dbg(FYI, "rc: %d during invalidate phase\n", rc);
> >                         rc = 0; /* don't care about it in fsync */
> > @@ -2628,7 +2628,7 @@ cifs_strict_writev(struct kiocb *iocb, const struct iovec *iov,
> >                  * request comes - break it on the client to prevent reading
> >                  * an old data.
> >                  */
> > -               cifs_invalidate_mapping(inode);
> > +               cifs_zap_mapping(inode);
> >                 cifs_dbg(FYI, "Set no oplock for inode=%p after a write operation\n",
> >                          inode);
> >                 cinode->oplock = 0;
> > @@ -3125,7 +3125,7 @@ int cifs_file_strict_mmap(struct file *file, struct vm_area_struct *vma)
> >         xid = get_xid();
> >
> >         if (!CIFS_CACHE_READ(CIFS_I(inode))) {
> > -               rc = cifs_invalidate_mapping(inode);
> > +               rc = cifs_zap_mapping(inode);
> >                 if (rc)
> >                         return rc;
> >         }
> > @@ -3669,7 +3669,7 @@ void cifs_oplock_break(struct work_struct *work)
> >                 if (!CIFS_CACHE_READ(cinode)) {
> >                         rc = filemap_fdatawait(inode->i_mapping);
> >                         mapping_set_error(inode->i_mapping, rc);
> > -                       cifs_invalidate_mapping(inode);
> > +                       cifs_zap_mapping(inode);
> >                 }
> >                 cifs_dbg(FYI, "Oplock flush inode %p rc %d\n", inode, rc);
> >         }
> > diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
> > index 39b76bac196d..b840930f6271 100644
> > --- a/fs/cifs/inode.c
> > +++ b/fs/cifs/inode.c
> > @@ -22,6 +22,7 @@
> >  #include <linux/stat.h>
> >  #include <linux/slab.h>
> >  #include <linux/pagemap.h>
> > +#include <linux/freezer.h>
> >  #include <asm/div64.h>
> >  #include "cifsfs.h"
> >  #include "cifspdu.h"
> > @@ -1762,29 +1763,60 @@ int
> >  cifs_invalidate_mapping(struct inode *inode)
> >  {
> >         int rc = 0;
> > -       struct cifsInodeInfo *cifs_i = CIFS_I(inode);
> > -
> > -       clear_bit(CIFS_INO_INVALID_MAPPING, &cifs_i->flags);
> >
> >         if (inode->i_mapping && inode->i_mapping->nrpages != 0) {
> >                 rc = invalidate_inode_pages2(inode->i_mapping);
> > -               if (rc) {
> > +               if (rc)
> >                         cifs_dbg(VFS, "%s: could not invalidate inode %p\n",
> >                                  __func__, inode);
> > -                       set_bit(CIFS_INO_INVALID_MAPPING, &cifs_i->flags);
> > -               }
> >         }
> >
> >         cifs_fscache_reset_inode_cookie(inode);
> >         return rc;
> >  }
> >
> > +/**
> > + * cifs_wait_bit_killable - helper for functions that are sleeping on bit locks
> > + * @word: long word containing the bit lock
> > + */
> > +static int
> > +cifs_wait_bit_killable(void *word)
> > +{
> > +       if (fatal_signal_pending(current))
> > +               return -ERESTARTSYS;
> > +       freezable_schedule_unsafe();
> > +       return 0;
> > +}
> > +
> >  int
> >  cifs_revalidate_mapping(struct inode *inode)
> >  {
> > -       if (test_bit(CIFS_INODE_INVALID_MAPPING, &CIFS_I(inode)->flags));
> > -               return cifs_invalidate_mapping(inode);
> > -       return 0;
> > +       int rc;
> > +       unsigned long *flags = &CIFS_I(inode)->flags;
> > +
> > +       rc = wait_on_bit_lock(flags, CIFS_INO_LOCK, cifs_wait_bit_killable,
> > +                               TASK_KILLABLE);
> > +       if (rc)
> > +               return rc;
> > +
> > +       if (test_and_clear_bit(CIFS_INO_INVALID_MAPPING, flags)) {
> > +               rc = cifs_invalidate_mapping(inode);
> > +               if (rc)
> > +                       set_bit(CIFS_INO_INVALID_MAPPING, flags);
> > +       }
> > +
> > +        clear_bit_unlock(CIFS_INO_LOCK, flags);
> > +        smp_mb__after_clear_bit();
> > +        wake_up_bit(flags, CIFS_INO_LOCK);
> > +
> > +       return rc;
> > +}
> > +
> > +int
> > +cifs_zap_mapping(struct inode *inode)
> > +{
> > +       set_bit(CIFS_INO_INVALID_MAPPING, &CIFS_I(inode)->flags);
> > +       return cifs_revalidate_mapping(inode);
> >  }
> >
> >  int cifs_revalidate_file_attr(struct file *filp)
> > --
> > 1.9.0
> >
> 
> 
>
diff mbox

Patch

diff --git a/fs/cifs/cifsfs.h b/fs/cifs/cifsfs.h
index 40d5a4df1e38..b7cf9ee7654b 100644
--- a/fs/cifs/cifsfs.h
+++ b/fs/cifs/cifsfs.h
@@ -68,6 +68,7 @@  extern int cifs_revalidate_file(struct file *filp);
 extern int cifs_revalidate_dentry(struct dentry *);
 extern int cifs_invalidate_mapping(struct inode *inode);
 extern int cifs_revalidate_mapping(struct inode *inode);
+extern int cifs_zap_mapping(struct inode *inode);
 extern int cifs_getattr(struct vfsmount *, struct dentry *, struct kstat *);
 extern int cifs_setattr(struct dentry *, struct iattr *);
 
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 0d4a1039ac27..84cd4447cc31 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -1111,6 +1111,7 @@  struct cifsInodeInfo {
 	__u32 cifsAttrs; /* e.g. DOS archive bit, sparse, compressed, system */
 	unsigned int oplock;		/* oplock/lease level we have */
 	unsigned int epoch;		/* used to track lease state changes */
+#define CIFS_INO_LOCK			(0)
 #define CIFS_INO_DELETE_PENDING		(1)
 #define CIFS_INO_INVALID_MAPPING	(2)
 	unsigned long flags;		/* flags field */
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 784b17d510fc..ccca61803f0a 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -335,7 +335,7 @@  cifs_new_fileinfo(struct cifs_fid *fid, struct file *file,
 	spin_unlock(&cifs_file_list_lock);
 
 	if (fid->purge_cache)
-		cifs_invalidate_mapping(inode);
+		cifs_zap_mapping(inode);
 
 	file->private_data = cfile;
 	return cfile;
@@ -1529,7 +1529,7 @@  cifs_setlk(struct file *file, struct file_lock *flock, __u32 type,
 		 */
 		if (!CIFS_CACHE_WRITE(CIFS_I(inode)) &&
 					CIFS_CACHE_READ(CIFS_I(inode))) {
-			cifs_invalidate_mapping(inode);
+			cifs_zap_mapping(inode);
 			cifs_dbg(FYI, "Set no oplock for inode=%p due to mand locks\n",
 				 inode);
 			CIFS_I(inode)->oplock = 0;
@@ -2218,7 +2218,7 @@  int cifs_strict_fsync(struct file *file, loff_t start, loff_t end,
 		 file->f_path.dentry->d_name.name, datasync);
 
 	if (!CIFS_CACHE_READ(CIFS_I(inode))) {
-		rc = cifs_invalidate_mapping(inode);
+		rc = cifs_zap_mapping(inode);
 		if (rc) {
 			cifs_dbg(FYI, "rc: %d during invalidate phase\n", rc);
 			rc = 0; /* don't care about it in fsync */
@@ -2628,7 +2628,7 @@  cifs_strict_writev(struct kiocb *iocb, const struct iovec *iov,
 		 * request comes - break it on the client to prevent reading
 		 * an old data.
 		 */
-		cifs_invalidate_mapping(inode);
+		cifs_zap_mapping(inode);
 		cifs_dbg(FYI, "Set no oplock for inode=%p after a write operation\n",
 			 inode);
 		cinode->oplock = 0;
@@ -3125,7 +3125,7 @@  int cifs_file_strict_mmap(struct file *file, struct vm_area_struct *vma)
 	xid = get_xid();
 
 	if (!CIFS_CACHE_READ(CIFS_I(inode))) {
-		rc = cifs_invalidate_mapping(inode);
+		rc = cifs_zap_mapping(inode);
 		if (rc)
 			return rc;
 	}
@@ -3669,7 +3669,7 @@  void cifs_oplock_break(struct work_struct *work)
 		if (!CIFS_CACHE_READ(cinode)) {
 			rc = filemap_fdatawait(inode->i_mapping);
 			mapping_set_error(inode->i_mapping, rc);
-			cifs_invalidate_mapping(inode);
+			cifs_zap_mapping(inode);
 		}
 		cifs_dbg(FYI, "Oplock flush inode %p rc %d\n", inode, rc);
 	}
diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index 39b76bac196d..b840930f6271 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -22,6 +22,7 @@ 
 #include <linux/stat.h>
 #include <linux/slab.h>
 #include <linux/pagemap.h>
+#include <linux/freezer.h>
 #include <asm/div64.h>
 #include "cifsfs.h"
 #include "cifspdu.h"
@@ -1762,29 +1763,60 @@  int
 cifs_invalidate_mapping(struct inode *inode)
 {
 	int rc = 0;
-	struct cifsInodeInfo *cifs_i = CIFS_I(inode);
-
-	clear_bit(CIFS_INO_INVALID_MAPPING, &cifs_i->flags);
 
 	if (inode->i_mapping && inode->i_mapping->nrpages != 0) {
 		rc = invalidate_inode_pages2(inode->i_mapping);
-		if (rc) {
+		if (rc)
 			cifs_dbg(VFS, "%s: could not invalidate inode %p\n",
 				 __func__, inode);
-			set_bit(CIFS_INO_INVALID_MAPPING, &cifs_i->flags);
-		}
 	}
 
 	cifs_fscache_reset_inode_cookie(inode);
 	return rc;
 }
 
+/**
+ * cifs_wait_bit_killable - helper for functions that are sleeping on bit locks
+ * @word: long word containing the bit lock
+ */
+static int
+cifs_wait_bit_killable(void *word)
+{
+	if (fatal_signal_pending(current))
+		return -ERESTARTSYS;
+	freezable_schedule_unsafe();
+	return 0;
+}
+
 int
 cifs_revalidate_mapping(struct inode *inode)
 {
-	if (test_bit(CIFS_INODE_INVALID_MAPPING, &CIFS_I(inode)->flags));
-		return cifs_invalidate_mapping(inode);
-	return 0;
+	int rc;
+	unsigned long *flags = &CIFS_I(inode)->flags;
+
+	rc = wait_on_bit_lock(flags, CIFS_INO_LOCK, cifs_wait_bit_killable,
+				TASK_KILLABLE);
+	if (rc)
+		return rc;
+
+	if (test_and_clear_bit(CIFS_INO_INVALID_MAPPING, flags)) {
+		rc = cifs_invalidate_mapping(inode);
+		if (rc)
+			set_bit(CIFS_INO_INVALID_MAPPING, flags);
+	}
+
+        clear_bit_unlock(CIFS_INO_LOCK, flags);
+        smp_mb__after_clear_bit();
+        wake_up_bit(flags, CIFS_INO_LOCK);
+
+	return rc;
+}
+
+int
+cifs_zap_mapping(struct inode *inode)
+{
+	set_bit(CIFS_INO_INVALID_MAPPING, &CIFS_I(inode)->flags);
+	return cifs_revalidate_mapping(inode);
 }
 
 int cifs_revalidate_file_attr(struct file *filp)