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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: Bob Peterson <rpeterso@redhat.com>
zero-colors
Bob Peterson 2017-08-30 09:26:09 -05:00
parent d296b15ed5
commit c4a9d1892f
1 changed files with 16 additions and 3 deletions
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19
fs/gfs2/bmap.c
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@ -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,