[Cluster-devel] [PATCH] GFS2: Don't call file_accessed() with a shared glock

[Cluster-devel] [PATCH] GFS2: Don't call file_accessed() with a shared glock

[Benjamin Marzinski]

file_accessed() was being called by gfs2_mmap() with a shared glock. If it
needed to update the atime, it was crashing because it dirtied the inode in
gfs2_dirty_inode() without holding an exclusive lock. gfs2_dirty_inode()
checked if the caller was already holding a glock, but it didn't make sure that
the glock was in the exclusive state. Now, instead of calling file_accessed()
while holding the shared lock in gfs2_mmap(), file_accessed() is called after
grabbing and releasing the glock to update the inode.  If file_accessed() needs
to update the atime, it will grab an exclusive lock in gfs2_dirty_inode().

gfs2_dirty_inode() now also checks to make sure that if the calling process has
already locked the glock, it has an exclusive lock.

Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
---
 fs/gfs2/file.c  |   12 +++++-------
 fs/gfs2/super.c |    3 ++-
 2 files changed, 7 insertions(+), 8 deletions(-)

Index: gfs2-3.0-nmw/fs/gfs2/file.c
===================================================================
--- gfs2-3.0-nmw.orig/fs/gfs2/file.c
+++ gfs2-3.0-nmw/fs/gfs2/file.c
@@ -516,15 +516,13 @@ static int gfs2_mmap(struct file *file,
 		struct gfs2_holder i_gh;
 		int error;
 
-		gfs2_holder_init(ip->i_gl, LM_ST_SHARED, LM_FLAG_ANY, &i_gh);
-		error = gfs2_glock_nq(&i_gh);
-		if (error == 0) {
-			file_accessed(file);
-			gfs2_glock_dq(&i_gh);
-		}
-		gfs2_holder_uninit(&i_gh);
+		error = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, LM_FLAG_ANY,
+					   &i_gh);
 		if (error)
 			return error;
+		/* grab lock to update inode */
+		gfs2_glock_dq_uninit(&i_gh);
+		file_accessed(file);
 	}
 	vma->vm_ops = &gfs2_vm_ops;
 
Index: gfs2-3.0-nmw/fs/gfs2/super.c
===================================================================
--- gfs2-3.0-nmw.orig/fs/gfs2/super.c
+++ gfs2-3.0-nmw/fs/gfs2/super.c
@@ -810,7 +810,8 @@ static void gfs2_dirty_inode(struct inod
 			return;
 		}
 		need_unlock = 1;
-	}
+	} else if (WARN_ON_ONCE(ip->i_gl->gl_state != LM_ST_EXCLUSIVE))
+		return;
 
 	if (current->journal_info == NULL) {
 		ret = gfs2_trans_begin(sdp, RES_DINODE, 0);

[Cluster-devel] [PATCH] GFS2: Don't call file_accessed() with a shared glock

[Steven Whitehouse]

Hi,

Looks good. Pushed to the -nmw tree. Thanks,

Steve.

On Tue, 2012-11-06 at 00:49 -0600, Benjamin Marzinski wrote:
> file_accessed() was being called by gfs2_mmap() with a shared glock. If it
> needed to update the atime, it was crashing because it dirtied the inode in
> gfs2_dirty_inode() without holding an exclusive lock. gfs2_dirty_inode()
> checked if the caller was already holding a glock, but it didn't make sure that
> the glock was in the exclusive state. Now, instead of calling file_accessed()
> while holding the shared lock in gfs2_mmap(), file_accessed() is called after
> grabbing and releasing the glock to update the inode.  If file_accessed() needs
> to update the atime, it will grab an exclusive lock in gfs2_dirty_inode().
> 
> gfs2_dirty_inode() now also checks to make sure that if the calling process has
> already locked the glock, it has an exclusive lock.
> 
> Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
> ---
>  fs/gfs2/file.c  |   12 +++++-------
>  fs/gfs2/super.c |    3 ++-
>  2 files changed, 7 insertions(+), 8 deletions(-)
> 
> Index: gfs2-3.0-nmw/fs/gfs2/file.c
> ===================================================================
> --- gfs2-3.0-nmw.orig/fs/gfs2/file.c
> +++ gfs2-3.0-nmw/fs/gfs2/file.c
> @@ -516,15 +516,13 @@ static int gfs2_mmap(struct file *file,
>  		struct gfs2_holder i_gh;
>  		int error;
>  
> -		gfs2_holder_init(ip->i_gl, LM_ST_SHARED, LM_FLAG_ANY, &i_gh);
> -		error = gfs2_glock_nq(&i_gh);
> -		if (error == 0) {
> -			file_accessed(file);
> -			gfs2_glock_dq(&i_gh);
> -		}
> -		gfs2_holder_uninit(&i_gh);
> +		error = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, LM_FLAG_ANY,
> +					   &i_gh);
>  		if (error)
>  			return error;
> +		/* grab lock to update inode */
> +		gfs2_glock_dq_uninit(&i_gh);
> +		file_accessed(file);
>  	}
>  	vma->vm_ops = &gfs2_vm_ops;
>  
> Index: gfs2-3.0-nmw/fs/gfs2/super.c
> ===================================================================
> --- gfs2-3.0-nmw.orig/fs/gfs2/super.c
> +++ gfs2-3.0-nmw/fs/gfs2/super.c
> @@ -810,7 +810,8 @@ static void gfs2_dirty_inode(struct inod
>  			return;
>  		}
>  		need_unlock = 1;
> -	}
> +	} else if (WARN_ON_ONCE(ip->i_gl->gl_state != LM_ST_EXCLUSIVE))
> +		return;
>  
>  	if (current->journal_info == NULL) {
>  		ret = gfs2_trans_begin(sdp, RES_DINODE, 0);
>