From: jeffm@suse.com
To: linux-btrfs@vger.kernel.org
Cc: Jeff Mahoney <jeffm@suse.com>
Subject: [PATCH 3/7] btrfs: skip superblocks during discard
Date: Mon, 15 Jun 2015 09:41:16 -0400 [thread overview]
Message-ID: <1434375680-4115-3-git-send-email-jeffm@suse.com> (raw)
In-Reply-To: <557ED6DC.6070900@suse.com>
From: Jeff Mahoney <jeffm@suse.com>
Btrfs doesn't track superblocks with extent records so there is nothing
persistent on-disk to indicate that those blocks are in use. We track
the superblocks in memory to ensure they don't get used by removing them
from the free space cache when we load a block group from disk. Prior
to 47ab2a6c6a (Btrfs: remove empty block groups automatically), that
was fine since the block group would never be reclaimed so the superblock
was always safe. Once we started removing the empty block groups, we
were protected by the fact that discards weren't being properly issued
for unused space either via FITRIM or -odiscard. The block groups were
still being released, but the blocks remained on disk.
In order to properly discard unused block groups, we need to filter out
the superblocks from the discard range. Superblocks are located at fixed
locations on each device, so it makes sense to filter them out in
btrfs_issue_discard, which is used by both -odiscard and FITRIM.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
---
fs/btrfs/extent-tree.c | 59 ++++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 55 insertions(+), 4 deletions(-)
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index cf9cefd..1e44b93 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -1884,10 +1884,12 @@ static int remove_extent_backref(struct btrfs_trans_handle *trans,
return ret;
}
+#define in_range(b, first, len) ((b) >= (first) && (b) < (first) + (len))
static int btrfs_issue_discard(struct block_device *bdev, u64 start, u64 len,
u64 *discarded_bytes)
{
- int ret = 0;
+ int j, ret = 0;
+ u64 bytes_left, end;
u64 aligned_start = ALIGN(start, 1 << 9);
if (WARN_ON(start != aligned_start)) {
@@ -1897,11 +1899,60 @@ static int btrfs_issue_discard(struct block_device *bdev, u64 start, u64 len,
}
*discarded_bytes = 0;
- if (len) {
- ret = blkdev_issue_discard(bdev, start >> 9, len >> 9,
+
+ if (!len)
+ return 0;
+
+ end = start + len;
+ bytes_left = len;
+
+ /* Skip any superblocks on this device. */
+ for (j = 0; j < BTRFS_SUPER_MIRROR_MAX; j++) {
+ u64 sb_start = btrfs_sb_offset(j);
+ u64 sb_end = sb_start + BTRFS_SUPER_INFO_SIZE;
+ u64 size = sb_start - start;
+
+ if (!in_range(sb_start, start, bytes_left) &&
+ !in_range(sb_end, start, bytes_left) &&
+ !in_range(start, sb_start, BTRFS_SUPER_INFO_SIZE))
+ continue;
+
+ /*
+ * Superblock spans beginning of range. Adjust start and
+ * try again.
+ */
+ if (sb_start <= start) {
+ start += sb_end - start;
+ if (start > end) {
+ bytes_left = 0;
+ break;
+ }
+ bytes_left = end - start;
+ continue;
+ }
+
+ if (size) {
+ ret = blkdev_issue_discard(bdev, start >> 9, size >> 9,
+ GFP_NOFS, 0);
+ if (!ret)
+ *discarded_bytes += size;
+ else if (ret != -EOPNOTSUPP)
+ return ret;
+ }
+
+ start = sb_end;
+ if (start > end) {
+ bytes_left = 0;
+ break;
+ }
+ bytes_left = end - start;
+ }
+
+ if (bytes_left) {
+ ret = blkdev_issue_discard(bdev, start >> 9, bytes_left >> 9,
GFP_NOFS, 0);
if (!ret)
- *discarded_bytes = len;
+ *discarded_bytes += bytes_left;
}
return ret;
}
--
2.4.3
next prev parent reply other threads:[~2015-06-15 13:41 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-15 13:45 [PATCH v5] btrfs: fix automatic blockgroup remove + discard Jeff Mahoney
2015-06-15 13:41 ` [PATCH 1/7] btrfs: make btrfs_issue_discard return bytes discarded jeffm
2015-06-17 9:53 ` Filipe David Manana
2015-06-15 13:41 ` [PATCH 2/7] btrfs: btrfs_issue_discard ensure offset/length are aligned to sector boundaries jeffm
2015-06-17 9:55 ` Filipe David Manana
2015-06-15 13:41 ` jeffm [this message]
2015-06-17 9:57 ` [PATCH 3/7] btrfs: skip superblocks during discard Filipe David Manana
2015-06-15 13:41 ` [PATCH 4/7] btrfs: iterate over unused chunk space in FITRIM jeffm
2015-06-17 10:03 ` Filipe David Manana
2015-06-15 13:41 ` [PATCH 5/7] btrfs: explictly delete unused block groups in close_ctree and ro-remount jeffm
2015-06-17 10:04 ` Filipe David Manana
2015-06-17 13:24 ` Filipe David Manana
2015-06-17 14:32 ` Jeff Mahoney
2015-06-17 14:36 ` Jeff Mahoney
2015-06-17 14:37 ` Filipe David Manana
2015-06-15 13:41 ` [PATCH 6/7] btrfs: add missing discards when unpinning extents with -o discard jeffm
2015-06-17 10:07 ` Filipe David Manana
2015-06-15 13:41 ` [PATCH 7/7] btrfs: cleanup, stop casting for extent_map->lookup everywhere jeffm
2015-06-17 10:08 ` Filipe David Manana
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