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GFS2: Introduce helper for clearing gl_object 

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
View File

@ -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__ */

4
fs/gfs2/inode.c
View File

@ -201,14 +201,14 @@ struct inode *gfs2_inode_lookup(struct super_block *sb, unsigned int type,
fail_refresh:
ip->i_iopen_gh.gh_flags |= GL_NOCACHE;
glock_set_object(ip->i_iopen_gh.gh_gl, NULL);
glock_clear_object(ip->i_iopen_gh.gh_gl, ip);
gfs2_glock_dq_uninit(&ip->i_iopen_gh);
fail_put:
if (io_gl)
gfs2_glock_put(io_gl);
if (gfs2_holder_initialized(&i_gh))
gfs2_glock_dq_uninit(&i_gh);
glock_set_object(ip->i_gl, NULL);
glock_clear_object(ip->i_gl, ip);
fail:
iget_failed(inode);
return ERR_PTR(error);

4
fs/gfs2/super.c
View File

@ -1640,13 +1640,13 @@ out:
gfs2_ordered_del_inode(ip);
clear_inode(inode);
gfs2_dir_hash_inval(ip);
glock_set_object(ip->i_gl, NULL);
glock_clear_object(ip->i_gl, ip);
wait_on_bit_io(&ip->i_flags, GIF_GLOP_PENDING, TASK_UNINTERRUPTIBLE);
gfs2_glock_add_to_lru(ip->i_gl);
gfs2_glock_put(ip->i_gl);
ip->i_gl = NULL;
if (gfs2_holder_initialized(&ip->i_iopen_gh)) {
glock_set_object(ip->i_iopen_gh.gh_gl, NULL);
glock_clear_object(ip->i_iopen_gh.gh_gl, ip);
ip->i_iopen_gh.gh_flags |= GL_NOCACHE;
gfs2_glock_dq_uninit(&ip->i_iopen_gh);
}