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@xxxxxxxxxxxxxx>
---
fs/btrfs/ioctl.c | 37 ++++++++++++++++++++++++++-----------
1 files changed, 26 insertions(+), 11 deletions(-)
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 57aa5b7..90d7904 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -760,7 +760,7 @@ static int should_defrag_range(struct inode *inode, u64 start, u64 len,
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)
@@ -805,7 +805,6 @@ static int should_defrag_range(struct inode *inode, u64 start, u64 len,
* 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;
@@ -978,13 +977,14 @@ int btrfs_defrag_file(struct inode *inode, struct file *file,
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;
@@ -1014,7 +1014,7 @@ int btrfs_defrag_file(struct inode *inode, struct file *file,
ra = &file->f_ra;
}
- pages = kmalloc(sizeof(struct page *) * newer_cluster,
+ pages = kmalloc(sizeof(struct page *) * max_cluster,
GFP_NOFS);
if (!pages) {
ret = -ENOMEM;
@@ -1039,7 +1039,6 @@ int btrfs_defrag_file(struct inode *inode, struct file *file,
* the extents in the file evenly spaced
*/
i = (newer_off & new_align) >> PAGE_CACHE_SHIFT;
- newer_left = newer_cluster;
} else
goto out_ra;
} else {
@@ -1071,12 +1070,26 @@ int btrfs_defrag_file(struct inode *inode, struct file *file,
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;
@@ -1096,15 +1109,17 @@ int btrfs_defrag_file(struct inode *inode, struct file *file,
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;
+ }
}
}
--
1.7.3.1
--
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