Btrfs: honor extent thresh during defragmentation
We won't defrag an extent, if it's bigger than the threshold we
specified and there's no small extent before it, but actually
the code doesn't work this way.
There are three bugs:
- When should_defrag_range() decides we should keep on defragmenting
an extent, last_len is not incremented. (old bug)
- The length that passes to should_defrag_range() is not the length
we're going to defrag. (new bug)
- We always defrag 256K bytes data, and a big extent can be part of
this range. (new bug)
For a file with 4 extents:
| 4K | 4K | 256K | 256K |
The result of defrag with (the default) 256K extent thresh should be:
| 264K | 256K |
but with those bugs, we'll get:
| 520K |
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index f902641..d524b66 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -765,7 +765,7 @@
int ret = 1;
/*
- * make sure that once we start defragging and extent, we keep on
+ * make sure that once we start defragging an extent, we keep on
* defragging it
*/
if (start < *defrag_end)
@@ -810,7 +810,6 @@
* extent will force at least part of that big extent to be defragged.
*/
if (ret) {
- *last_len += len;
*defrag_end = extent_map_end(em);
} else {
*last_len = 0;
@@ -984,13 +983,14 @@
u64 skip = 0;
u64 defrag_end = 0;
u64 newer_off = range->start;
- int newer_left = 0;
unsigned long i;
+ unsigned long ra_index = 0;
int ret;
int defrag_count = 0;
int compress_type = BTRFS_COMPRESS_ZLIB;
int extent_thresh = range->extent_thresh;
- int newer_cluster = (256 * 1024) >> PAGE_CACHE_SHIFT;
+ int max_cluster = (256 * 1024) >> PAGE_CACHE_SHIFT;
+ int cluster = max_cluster;
u64 new_align = ~((u64)128 * 1024 - 1);
struct page **pages = NULL;
@@ -1020,7 +1020,7 @@
ra = &file->f_ra;
}
- pages = kmalloc(sizeof(struct page *) * newer_cluster,
+ pages = kmalloc(sizeof(struct page *) * max_cluster,
GFP_NOFS);
if (!pages) {
ret = -ENOMEM;
@@ -1045,7 +1045,6 @@
* the extents in the file evenly spaced
*/
i = (newer_off & new_align) >> PAGE_CACHE_SHIFT;
- newer_left = newer_cluster;
} else
goto out_ra;
} else {
@@ -1077,12 +1076,26 @@
i = max(i + 1, next);
continue;
}
+
+ if (!newer_than) {
+ cluster = (PAGE_CACHE_ALIGN(defrag_end) >>
+ PAGE_CACHE_SHIFT) - i;
+ cluster = min(cluster, max_cluster);
+ } else {
+ cluster = max_cluster;
+ }
+
if (range->flags & BTRFS_DEFRAG_RANGE_COMPRESS)
BTRFS_I(inode)->force_compress = compress_type;
- btrfs_force_ra(inode->i_mapping, ra, file, i, newer_cluster);
+ if (i + cluster > ra_index) {
+ ra_index = max(i, ra_index);
+ btrfs_force_ra(inode->i_mapping, ra, file, ra_index,
+ cluster);
+ ra_index += max_cluster;
+ }
- ret = cluster_pages_for_defrag(inode, pages, i, newer_cluster);
+ ret = cluster_pages_for_defrag(inode, pages, i, cluster);
if (ret < 0)
goto out_ra;
@@ -1102,15 +1115,17 @@
if (!ret) {
range->start = newer_off;
i = (newer_off & new_align) >> PAGE_CACHE_SHIFT;
- newer_left = newer_cluster;
} else {
break;
}
} else {
- if (ret > 0)
+ if (ret > 0) {
i += ret;
- else
+ last_len += ret << PAGE_CACHE_SHIFT;
+ } else {
i++;
+ last_len = 0;
+ }
}
}