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btrfs-progs: docs: move the rescue fix-device-size command and update

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The subcommands are supposed to be in alphabetical order, move it to the
right spot and reword.

Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
David Sterba 2017-11-14 16:16:54 +01:00
parent f181e18f46
commit 561e6da458
1 changed files with 20 additions and 29 deletions
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49
Documentation/btrfs-rescue.asciidoc
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@ -15,6 +15,7 @@ DESCRIPTION
SUBCOMMAND
----------
*chunk-recover* [options] <device>::
Recover the chunk tree by scanning the devices
+
@ -30,6 +31,25 @@ help.
NOTE: Since *chunk-recover* will scan the whole device, it will be *VERY* slow
especially executed on a large device.
*fix-device-size* <device>::
fix device size and super block total bytes values that are do not match
+
Kernel 4.11 starts to check the device size more strictly and this might
mismatch the stored value of total bytes. See the exact error message below.
Newer kernel will refuse to mount the filesystem where the values do not match.
This error is not fatal and can be fixed. This command will fix the device
size values if possible.
+
----
BTRFS error (device sdb): super_total_bytes 92017859088384 mismatch with fs_devices total_rw_bytes 92017859094528
----
+
The mismatch may also exhibit as a kernel warning:
+
----
WARNING: CPU: 3 PID: 439 at fs/btrfs/ctree.h:1559 btrfs_update_device+0x1c5/0x1d0 [btrfs]
----
*super-recover* [options] <device>::
Recover bad superblocks from good copies.
+
@ -73,35 +93,6 @@ the log and the filesystem may be mounted normally again. The keywords to look
for are 'open_ctree' which says that it's during mount and function names
that contain 'replay', 'recover' or 'log_tree'.
*fix-device-size* <device>::
fix device size and super block total bytes
+
This command will fix the following problems, by re-aligning all devices' total
bytes and re-calculating super block total bytes.
+
1. Newer kernel refuse to mount btrfs caused by mismatch super block total bytes
+
----
BTRFS error (device sdb): super_total_bytes 92017859088384 mismatch with fs_devices total_rw_bytes 92017859094528
----
+
2. Noisy kernel warning for newer kernels
+
----
WARNING: CPU: 3 PID: 439 at fs/btrfs/ctree.h:1559 btrfs_update_device+0x1c5/0x1d0 [btrfs]
----
+
And the corresponding line is the `WARN_ON()` line below:
+
----
{
BUILD_BUG_ON(sizeof(u64) !=
sizeof(((struct btrfs_dev_item *)0))->total_bytes);
WARN_ON(!IS_ALIGNED(val, eb->fs_info->sectorsize));
btrfs_set_64(eb, s, offsetof(struct btrfs_dev_item, total_bytes), val);
}
----
EXIT STATUS
-----------
*btrfs rescue* returns a zero exit status if it succeeds. Non zero is