On 2017-12-08 02:57, Anand Jain wrote:
-EXPERIMENTAL-
As of now when primary SB fails we won't self heal and would fail mount,
this is an experimental patch which thinks why not go and read backup
copy.
I like the concept, and actually think this should be default behavior
on a filesystem that's already mounted (we fix other errors, why not
SB's), but I don't think it should be default behavior at mount time for
the reasons Qu has outlined (picking up old BTRFS SB's after
reformatting is bad). However, I do think it's useful to be able to ask
for this behavior on mount, so that you don't need to fight with the
programs to get a filesystem to mount when the first SB is missing
(perhaps add a 'usebackupsb' option to mirror 'usebackuproot'?).
Signed-off-by: Anand Jain <anand.jain@xxxxxxxxxx>
---
fs/btrfs/disk-io.c | 8 +++++++-
fs/btrfs/volumes.c | 10 +++++++---
2 files changed, 14 insertions(+), 4 deletions(-)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 9b20c1f3563b..a791b8dfe8a8 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3190,7 +3190,7 @@ struct buffer_head *btrfs_read_dev_super(struct block_device *bdev)
* So, we need to add a special mount option to scan for
* later supers, using BTRFS_SUPER_MIRROR_MAX instead
*/
- for (i = 0; i < 1; i++) {
+ for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; i++) {
ret = btrfs_read_dev_one_super(bdev, i, &bh);
if (ret)
continue;
@@ -4015,11 +4015,17 @@ static int btrfs_check_super_valid(struct btrfs_fs_info *fs_info)
ret = -EINVAL;
}
+#if 0
+ /*
+ * Need a way to check for any copy of SB, as its not a
+ * strong check, just ignore this for now.
+ */
if (btrfs_super_bytenr(sb) != BTRFS_SUPER_INFO_OFFSET) {
btrfs_err(fs_info, "super offset mismatch %llu != %u",
btrfs_super_bytenr(sb), BTRFS_SUPER_INFO_OFFSET);
ret = -EINVAL;
}
+#endif
/*
* Obvious sys_chunk_array corruptions, it must hold at least one key
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 9fa2539a8493..f368db94d62b 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1369,7 +1369,7 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
{
struct btrfs_super_block *disk_super;
struct block_device *bdev;
- struct page *page;
+ struct buffer_head *sb_bh;
int ret = -EINVAL;
u64 devid;
u64 transid;
@@ -1392,8 +1392,12 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
goto error;
}
- if (btrfs_read_disk_super(bdev, bytenr, &page, &disk_super))
+ sb_bh = btrfs_read_dev_super(bdev);
+ if (IS_ERR(sb_bh)) {
+ ret = PTR_ERR(sb_bh);
goto error_bdev_put;
+ }
+ disk_super = (struct btrfs_super_block *) sb_bh->b_data;
devid = btrfs_stack_device_id(&disk_super->dev_item);
transid = btrfs_super_generation(disk_super);
@@ -1413,7 +1417,7 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
if (!ret && fs_devices_ret)
(*fs_devices_ret)->total_devices = total_devices;
- btrfs_release_disk_super(page);
+ brelse(sb_bh);
error_bdev_put:
blkdev_put(bdev, flags);
--
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