[Ocfs2-devel] [PATCH] ocfs2: Fix wrong search logic in __ocfs2_resv_find_window
Heming Zhao
heming.zhao at suse.com
Thu Apr 6 15:40:52 UTC 2023
** problem **
Current code triggers a defragfs bug [1]:
```
tw-tst:~ # defragfs.ocfs2 /mnt/test_from_dd1
defragfs.ocfs2 1.8.7
[ERROR]Move extent failed:"/mnt/test_from_dd1" - No space left on device
[ERROR]"/mnt/test_from_dd1":No space left on device
```
I added some debug messages in relevant functions. When above error
messages appeared, the la-window still had enough continuous bitmap
to use, the -ENOSPC is wrong.
** analysis **
__ocfs2_resv_find_window should use resv node from rb-tree to do linear
search. But current code logic uses un-managered area between two resvs.
The searching logic deviates from this func job, which should only focus
on reservation areas (when rb_root is non NULL). Another issue of
__ocfs2_resv_find_window is more inclined to generate inner fragment.
It doesn't search & consume existing reservations but be apt to create
new reservation item.
This patch pulls this func (__ocfs2_resv_find_window) to do what it
should do: search & consume resev. if this func fails to get suitable
bitmap area, caller ocfs2_resv_find_window fallbacks to use oldest
resv from LRU to do the final search.
[1]: https://bugzilla.suse.com/show_bug.cgi?id=1131931
Signed-off-by: Heming Zhao <heming.zhao at suse.com>
---
fs/ocfs2/reservations.c | 48 +++++++++++++++++++++++++++++------------
1 file changed, 34 insertions(+), 14 deletions(-)
diff --git a/fs/ocfs2/reservations.c b/fs/ocfs2/reservations.c
index a9d1296d736d..eda672622d1d 100644
--- a/fs/ocfs2/reservations.c
+++ b/fs/ocfs2/reservations.c
@@ -458,10 +458,11 @@ static void __ocfs2_resv_find_window(struct ocfs2_reservation_map *resmap,
{
struct rb_root *root = &resmap->m_reservations;
unsigned int gap_start, gap_end, gap_len;
- struct ocfs2_alloc_reservation *prev_resv, *next_resv;
+ struct ocfs2_alloc_reservation *prev_resv, *next_resv, *best_resv;
struct rb_node *prev, *next;
unsigned int cstart, clen;
unsigned int best_start = 0, best_len = 0;
+ int create_new = 0;
/*
* Nasty cases to consider:
@@ -540,8 +541,9 @@ static void __ocfs2_resv_find_window(struct ocfs2_reservation_map *resmap,
if (clen) {
best_len = clen;
best_start = cstart;
+ create_new = 1;
if (best_len == wanted)
- goto out_insert;
+ goto out_create;
}
prev_resv = next_resv;
@@ -557,13 +559,9 @@ static void __ocfs2_resv_find_window(struct ocfs2_reservation_map *resmap,
while (1) {
next = rb_next(prev);
if (next) {
- next_resv = rb_entry(next,
- struct ocfs2_alloc_reservation,
- r_node);
-
- gap_start = ocfs2_resv_end(prev_resv) + 1;
- gap_end = next_resv->r_start - 1;
- gap_len = gap_end - gap_start + 1;
+ gap_start = prev_resv->r_start;
+ gap_end = prev_resv->r_start + prev_resv->r_len - 1;
+ gap_len = prev_resv->r_len;
} else {
/*
* We're at the rightmost edge of the
@@ -575,8 +573,8 @@ static void __ocfs2_resv_find_window(struct ocfs2_reservation_map *resmap,
gap_end = resmap->m_bitmap_len - 1;
}
- trace_ocfs2_resv_find_window_next(next ? next_resv->r_start: -1,
- next ? ocfs2_resv_end(next_resv) : -1);
+ trace_ocfs2_resv_find_window_next(next ? prev_resv->r_start : -1,
+ next ? ocfs2_resv_end(prev_resv) : -1);
/*
* No need to check this gap if we have already found
* a larger region of free bits.
@@ -589,10 +587,16 @@ static void __ocfs2_resv_find_window(struct ocfs2_reservation_map *resmap,
if (clen == wanted) {
best_len = clen;
best_start = cstart;
- goto out_insert;
+ best_resv = prev_resv;
+ if (!next)
+ goto out_create;
+ else
+ goto out_insert;
} else if (clen > best_len) {
best_len = clen;
best_start = cstart;
+ best_resv = prev_resv;
+ create_new = 0;
}
next_resv:
@@ -604,12 +608,28 @@ static void __ocfs2_resv_find_window(struct ocfs2_reservation_map *resmap,
r_node);
}
-out_insert:
- if (best_len) {
+ if (!best_len)
+ return;
+
+ if (create_new) {
+out_create:
resv->r_start = best_start;
resv->r_len = best_len;
ocfs2_resv_insert(resmap, resv);
+ return;
}
+
+out_insert:
+ if (best_resv->r_len <= wanted) {
+ resv->r_start = best_start;
+ resv->r_len = best_len;
+ __ocfs2_resv_discard(resmap, best_resv);
+ } else {
+ best_resv->r_len -= best_len;
+ resv->r_start = ocfs2_resv_end(best_resv) + 1;
+ resv->r_len = best_len;
+ }
+ ocfs2_resv_insert(resmap, resv);
}
static void ocfs2_cannibalize_resv(struct ocfs2_reservation_map *resmap,
--
2.26.2
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