Commit c4a9d189 authored by Bob Peterson's avatar Bob Peterson
Browse files

GFS2: Fix non-recursive truncate bug 



Before this patch if you truncated a file to a smaller size it
wasn't freeing all the blocks properly. There are two reasons.

First, the metapath comparison was not comparing previous heights.
I added a function, mp_eq_to_hgt, which checks the metapath at
all heights prior to the target height.

Second, in function find_nonnull_ptr, it needed to zero out all
pointers for heights following the target height. Translated into
decimal integer terms, this way a number like 299, when incremented,
becomes 300, not 399. The 2 gets incremented to 3, and the following
digits need to be reset.

These two things allow the truncate state machine to properly find
the blocks it needs to delete.

Signed-off-by: default avatarBob Peterson <rpeterso@redhat.com>
parent d296b15e

fs/gfs2/bmap.c

+16 −3
Original line number Diff line number Diff line
@@ -1104,8 +1104,15 @@ static bool find_nonnull_ptr(struct gfs2_sbd *sdp, struct metapath *mp, 


	while (true) {

		ptr = metapointer(h, mp);

		if (*ptr) /* if we have a non-null pointer */

		if (*ptr) { /* if we have a non-null pointer */

			/* Now zero the metapath after the current height. */

			h++;

			if (h < GFS2_MAX_META_HEIGHT)

				memset(&mp->mp_list[h], 0,

				       (GFS2_MAX_META_HEIGHT - h) *

				       sizeof(mp->mp_list[0]));

			return true;

		}



		if (mp->mp_list[h] < ptrs)

			mp->mp_list[h]++;
@@ -1121,6 +1128,13 @@ enum dealloc_states { 
	DEALLOC_DONE = 3,       /* process complete */

};



static bool mp_eq_to_hgt(struct metapath *mp, __u16 *nbof, unsigned int h)

{

	if (memcmp(mp->mp_list, nbof, h * sizeof(mp->mp_list[0])))

		return false;

	return true;

}



/**

 * trunc_dealloc - truncate a file down to a desired size

 * @ip: inode to truncate
@@ -1198,8 +1212,7 @@ static int trunc_dealloc(struct gfs2_inode *ip, u64 newsize) 
			/* If we're truncating to a non-zero size and the mp is

			   at the beginning of file for the strip height, we

			   need to preserve the first metadata pointer. */

			preserve1 = (newsize &&

				     (mp.mp_list[mp_h] == nbof[mp_h]));

			preserve1 = (newsize && mp_eq_to_hgt(&mp, nbof, mp_h));

			bh = mp.mp_bh[mp_h];

			gfs2_assert_withdraw(sdp, bh);

			if (gfs2_assert_withdraw(sdp,

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