From: Zheng Liu <wenqing.lz@xxxxxxxxxx>
When orig_physical_cnt == donor_physical_cnt, we need to defrag a file
because a file could be written backwards. So that will make it look
like a contiguous extent but actually the physical blocks are reversed.
This case can be created artificially just like xfstests #218 does. The
following script can create it.
for I in `seq 9 -1 0`; do
dd if=/dev/zero of=$testfile bs=4k count=1 conv=notrunc \
seek=$I oflag=sync &>/dev/null
done
sudo filefrag -v $testfile
sudo e4defrag -v $testfile
sudo filefrag -v $testfile
Before applied this patch, the result of running script is like:
Filesystem type is: ef53
File size of /mnt/sda3/testfile is 40960 (10 blocks of 4096 bytes)
ext: logical_offset: physical_offset: length: expected: flags:
0: 0.. 0: 34825.. 34825: 1:
1: 1.. 1: 34824.. 34824: 1: 34826:
2: 2.. 2: 34823.. 34823: 1: 34825:
3: 3.. 3: 34822.. 34822: 1: 34824:
4: 4.. 4: 34821.. 34821: 1: 34823:
5: 5.. 5: 34820.. 34820: 1: 34822:
6: 6.. 6: 34819.. 34819: 1: 34821:
7: 7.. 7: 34818.. 34818: 1: 34820:
8: 8.. 8: 34817.. 34817: 1: 34819:
9: 9.. 9: 34816.. 34816: 1: 34818: eof
/mnt/sda3/testfile: 10 extents found
ext4 defragmentation for /mnt/sda3/testfile
[1/1]/mnt/sda3/testfile: 100% extents: 10 -> 10 [ OK ]
Success: [1/1]
Filesystem type is: ef53
File size of /mnt/sda3/testfile is 40960 (10 blocks of 4096 bytes)
ext: logical_offset: physical_offset: length: expected: flags:
0: 0.. 0: 34825.. 34825: 1:
1: 1.. 1: 34824.. 34824: 1: 34826:
2: 2.. 2: 34823.. 34823: 1: 34825:
3: 3.. 3: 34822.. 34822: 1: 34824:
4: 4.. 4: 34821.. 34821: 1: 34823:
5: 5.. 5: 34820.. 34820: 1: 34822:
6: 6.. 6: 34819.. 34819: 1: 34821:
7: 7.. 7: 34818.. 34818: 1: 34820:
8: 8.. 8: 34817.. 34817: 1: 34819:
9: 9.. 9: 34816.. 34816: 1: 34818: eof
/mnt/sda3/testfile: 10 extents found
After applied it, the result of running script looks like:
Filesystem type is: ef53
File size of /mnt/sda3/testfile is 40960 (10 blocks of 4096 bytes)
ext: logical_offset: physical_offset: length: expected: flags:
0: 0.. 0: 34313.. 34313: 1:
1: 1.. 1: 34312.. 34312: 1: 34314:
2: 2.. 2: 34311.. 34311: 1: 34313:
3: 3.. 3: 34310.. 34310: 1: 34312:
4: 4.. 4: 34309.. 34309: 1: 34311:
5: 5.. 5: 34308.. 34308: 1: 34310:
6: 6.. 6: 34307.. 34307: 1: 34309:
7: 7.. 7: 34306.. 34306: 1: 34308:
8: 8.. 8: 34305.. 34305: 1: 34307:
9: 9.. 9: 34304.. 34304: 1: 34306: eof
/mnt/sda3/testfile: 10 extents found
ext4 defragmentation for /mnt/sda3/testfile
[1/1]/mnt/sda3/testfile: 100% extents: 10 -> 1 [ OK ]
Success: [1/1]
Filesystem type is: ef53
File size of /mnt/sda3/testfile is 40960 (10 blocks of 4096 bytes)
ext: logical_offset: physical_offset: length: expected: flags:
0: 0.. 9: 33794.. 33803: 10: eof
/mnt/sda3/testfile: 1 extent found
Signed-off-by: Zheng Liu <wenqing.lz@xxxxxxxxxx>
---
misc/e4defrag.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/misc/e4defrag.c b/misc/e4defrag.c
index 4b31d03..ae4e8d8 100644
--- a/misc/e4defrag.c
+++ b/misc/e4defrag.c
@@ -1649,7 +1649,7 @@ check_improvement:
}
if (file_frags_start <= best ||
- orig_physical_cnt <= donor_physical_cnt) {
+ orig_physical_cnt < donor_physical_cnt) {
printf("\033[79;0H\033[K[%u/%u]%s:\t%3d%%",
defraged_file_count, total_count, file, 100);
if (mode_flag & DETAIL)
--
1.7.12.rc2.18.g61b472e
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
