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UBIFS: fix debugging failure in dbg_check_space_info

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This patch fixes a debugging failure with which looks like this:
UBIFS error (pid 32313): dbg_check_space_info: free space changed from 6019344 to 6022654

The reason for this failure is described in the comment this patch adds
to the code. But in short - 'c->freeable_cnt' may be different before
and after re-mounting, and this is normal. So the debugging code should
make sure that free space calculations do not depend on 'c->freeable_cnt'.

A similar issue has been reported here:
http://lists.infradead.org/pipermail/linux-mtd/2011-April/034647.html

This patch should fix it.

For the -stable guys: this patch is only relevant for kernels 2.6.30
onwards.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Cc: stable@kernel.org [2.6.30+]
This commit is contained in:
Artem Bityutskiy 2011-04-04 17:16:39 +03:00
parent 9516953511
commit 7da6443aca
1 changed files with 36 additions and 5 deletions
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41
fs/ubifs/debug.c
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@ -972,11 +972,39 @@ void dbg_dump_index(struct ubifs_info *c)
void dbg_save_space_info(struct ubifs_info *c)
{
struct ubifs_debug_info *d = c->dbg;
ubifs_get_lp_stats(c, &d->saved_lst);
int freeable_cnt;
spin_lock(&c->space_lock);
memcpy(&d->saved_lst, &c->lst, sizeof(struct ubifs_lp_stats));
/*
* We use a dirty hack here and zero out @c->freeable_cnt, because it
* affects the free space calculations, and UBIFS might not know about
* all freeable eraseblocks. Indeed, we know about freeable eraseblocks
* only when we read their lprops, and we do this only lazily, upon the
* need. So at any given point of time @c->freeable_cnt might be not
* exactly accurate.
*
* Just one example about the issue we hit when we did not zero
* @c->freeable_cnt.
* 1. The file-system is mounted R/O, c->freeable_cnt is %0. We save the
* amount of free space in @d->saved_free
* 2. We re-mount R/W, which makes UBIFS to read the "lsave"
* information from flash, where we cache LEBs from various
* categories ('ubifs_remount_fs()' -> 'ubifs_lpt_init()'
* -> 'lpt_init_wr()' -> 'read_lsave()' -> 'ubifs_lpt_lookup()'
* -> 'ubifs_get_pnode()' -> 'update_cats()'
* -> 'ubifs_add_to_cat()').
* 3. Lsave contains a freeable eraseblock, and @c->freeable_cnt
* becomes %1.
* 4. We calculate the amount of free space when the re-mount is
* finished in 'dbg_check_space_info()' and it does not match
* @d->saved_free.
*/
freeable_cnt = c->freeable_cnt;
c->freeable_cnt = 0;
d->saved_free = ubifs_get_free_space_nolock(c);
c->freeable_cnt = freeable_cnt;
spin_unlock(&c->space_lock);
}
@ -993,12 +1021,15 @@ int dbg_check_space_info(struct ubifs_info *c)
{
struct ubifs_debug_info *d = c->dbg;
struct ubifs_lp_stats lst;
long long avail, free;
long long free;
int freeable_cnt;
spin_lock(&c->space_lock);
avail = ubifs_calc_available(c, c->min_idx_lebs);
freeable_cnt = c->freeable_cnt;
c->freeable_cnt = 0;
free = ubifs_get_free_space_nolock(c);
c->freeable_cnt = freeable_cnt;
spin_unlock(&c->space_lock);
free = ubifs_get_free_space(c);
if (free != d->saved_free) {
ubifs_err("free space changed from %lld to %lld",