RFC: This patch not for merging, but only for review and discussion.
When mounting, we consider only the primary superblock on each device.
But when writing the superblocks, we might silently ignore errors
from the primary superblock, if we succeeded to write secondary
superblocks. In such case, the primary superblock was not updated
properly, and if we crash at this point, later mount will use
an out-of-date superblock.
This patch changes the behavior to NOT IGNORING any errors on the primary
superblock,
and IGNORING any errors on secondary superblocks. This way, we always insist
on having
an up-to-date primary superblock.
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 4e47849..0ae9f7c 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3357,11 +3357,13 @@ static int write_dev_supers(struct btrfs_device
*device,
bh = __find_get_block(device->bdev, bytenr / 4096,
BTRFS_SUPER_INFO_SIZE);
if (!bh) {
- errors++;
+ /* we only care about primary superblock errors */
+ if (i == 0)
+ errors++;
continue;
}
wait_on_buffer(bh);
- if (!buffer_uptodate(bh))
+ if (!buffer_uptodate(bh) && i == 0)
errors++;
/* drop our reference */
@@ -3388,9 +3390,10 @@ static int write_dev_supers(struct btrfs_device
*device,
BTRFS_SUPER_INFO_SIZE);
if (!bh) {
btrfs_err(device->dev_root->fs_info,
- "couldn't get super buffer head for bytenr %llu",
- bytenr);
- errors++;
+ "couldn't get super buffer head for bytenr %llu (sb
copy %d)",
+ bytenr, i);
+ if (i == 0)
+ errors++;
continue;
}
@@ -3413,10 +3416,10 @@ static int write_dev_supers(struct btrfs_device
*device,
ret = btrfsic_submit_bh(WRITE_FUA, bh);
else
ret = btrfsic_submit_bh(WRITE_SYNC, bh);
- if (ret)
+ if (ret && i == 0)
errors++;
}
- return errors < i ? 0 : -1;
+ return errors ? -1 : 0;
}
/*
P.S.: when reviewing the code of write_dev_supers(), I also noticed that
when wait==0 and we hit an error in one __getblk(), then the caller
(write_all_supers) will not properly wait for submitted buffer-heads to
complete, and we won't do the additional "brelse(bh);", which wait==0 case
does. Is this a problem?
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