| Message ID | 1556247665-22859-1-git-send-email-johnnyc@synology.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | btrfs: Check the compression level before getting a workspace | expand |
On Fri, Apr 26, 2019 at 11:01:05AM +0800, Johnny Chang wrote: > When a file's compression property is set as zlib or zstd but leave > the compression mount option not be set, that means btrfs will try > to compress the file with default compression level. But in > btrfs_compress_pages(), it calls get_workspace() with level = 0. > This will return a workspace with a wrong compression level. > For zlib, the compression level in the workspace will be 0 > (that means "store only"). And for zstd, the compression in the > workspace will be 1, not the default level 3. > > How to reproduce: > mkfs -t btrfs /dev/sdb > mount /dev/sdb /mnt/ > mkdir /mnt/zlib > btrfs property set /mnt/zlib/ compression zlib > dd if=/dev/zero of=/mnt/zlib/compression-friendly-file-10M bs=1M count=10 > sync > btrfs-debugfs -f /mnt/zlib/compression-friendly-file-10M > > btrfs-debugfs output: > * before: > ... > (258 9961472): ram 524288 disk 1106247680 disk_size 524288 > file: ... extents 20 disk size 10485760 logical size 10485760 ratio 1.00 > > * after: > ... > (258 10354688): ram 131072 disk 14217216 disk_size 4096 > file: ... extents 80 disk size 327680 logical size 10485760 ratio 32.00 > > The steps for zstd are similar, but need to put a degging message to > show the level of the return workspace in zstd_get_workspace(). > > This commit adds a check of the compression level before getting a > workspace by set_level(). Good catch. I think it's safest set the level at btrfs_compress_pages though it means one extra call, compared to setting it when the property is set. This will change once the properties store the level too as it has to be combined with fs_info::compress_level. Reviewed-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c index 4f2a8ae..716656d 100644 --- a/fs/btrfs/compression.c +++ b/fs/btrfs/compression.c @@ -1009,6 +1009,7 @@ int btrfs_compress_pages(unsigned int type_level, struct address_space *mapping, struct list_head *workspace; int ret; + level = btrfs_compress_op[type]->set_level(level); workspace = get_workspace(type, level); ret = btrfs_compress_op[type]->compress_pages(workspace, mapping, start, pages,
When a file's compression property is set as zlib or zstd but leave the compression mount option not be set, that means btrfs will try to compress the file with default compression level. But in btrfs_compress_pages(), it calls get_workspace() with level = 0. This will return a workspace with a wrong compression level. For zlib, the compression level in the workspace will be 0 (that means "store only"). And for zstd, the compression in the workspace will be 1, not the default level 3. How to reproduce: mkfs -t btrfs /dev/sdb mount /dev/sdb /mnt/ mkdir /mnt/zlib btrfs property set /mnt/zlib/ compression zlib dd if=/dev/zero of=/mnt/zlib/compression-friendly-file-10M bs=1M count=10 sync btrfs-debugfs -f /mnt/zlib/compression-friendly-file-10M btrfs-debugfs output: * before: ... (258 9961472): ram 524288 disk 1106247680 disk_size 524288 file: ... extents 20 disk size 10485760 logical size 10485760 ratio 1.00 * after: ... (258 10354688): ram 131072 disk 14217216 disk_size 4096 file: ... extents 80 disk size 327680 logical size 10485760 ratio 32.00 The steps for zstd are similar, but need to put a degging message to show the level of the return workspace in zstd_get_workspace(). This commit adds a check of the compression level before getting a workspace by set_level(). Signed-off-by: Johnny Chang <johnnyc@synology.com> --- fs/btrfs/compression.c | 1 + 1 file changed, 1 insertion(+)