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GFS2: Introduce helper for clearing gl_object

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This patch introduces a new helper function in glock.h that
clears gl_object, with an added integrity check. An additional
integrity check has been added to glock_set_object, plus comments.
This is step 1 in a series to ensure gl_object integrity.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Reviewed-by: Andreas Gruenbacher <agruenba@redhat.com>
This commit is contained in:
Bob Peterson
2017-07-18 11:35:04 -05:00
parent e477b24b50
commit df3d87bde1
3 changed files with 38 additions and 4 deletions
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34
fs/gfs2/glock.h
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@@ -13,6 +13,7 @@
#include <linux/sched.h>
#include <linux/parser.h>
#include "incore.h"
#include "util.h"
/* Options for hostdata parser */
@@ -257,11 +258,44 @@ static inline bool gfs2_holder_initialized(struct gfs2_holder *gh)
return gh->gh_gl;
}
/**
* glock_set_object - set the gl_object field of a glock
* @gl: the glock
* @object: the object
*/
static inline void glock_set_object(struct gfs2_glock *gl, void *object)
{
spin_lock(&gl->gl_lockref.lock);
if (gfs2_assert_warn(gl->gl_name.ln_sbd, gl->gl_object == NULL))
gfs2_dump_glock(NULL, gl);
gl->gl_object = object;
spin_unlock(&gl->gl_lockref.lock);
}
/**
* glock_clear_object - clear the gl_object field of a glock
* @gl: the glock
* @object: the object
*
* I'd love to similarly add this:
* else if (gfs2_assert_warn(gl->gl_sbd, gl->gl_object == object))
* gfs2_dump_glock(NULL, gl);
* Unfortunately, that's not possible because as soon as gfs2_delete_inode
* frees the block in the rgrp, another process can reassign it for an I_NEW
* inode in gfs2_create_inode because that calls new_inode, not gfs2_iget.
* That means gfs2_delete_inode may subsequently try to call this function
* for a glock that's already pointing to a brand new inode. If we clear the
* new inode's gl_object, we'll introduce metadata corruption. Function
* gfs2_delete_inode calls clear_inode which calls gfs2_clear_inode which also
* tries to clear gl_object, so it's more than just gfs2_delete_inode.
*
*/
static inline void glock_clear_object(struct gfs2_glock *gl, void *object)
{
spin_lock(&gl->gl_lockref.lock);
if (gl->gl_object == object)
gl->gl_object = NULL;
spin_unlock(&gl->gl_lockref.lock);
}
#endif /* __GLOCK_DOT_H__ */