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Nikolay Borisov 7a62d0f073 btrfs: Handle one more split-brain scenario during fsid change
This commit continues hardening the scanning code to handle cases where
power loss could have caused disks in a multi-disk filesystem to be
in inconsistent state. Namely handle the situation that can occur when
some of the disks in multi-disk fs have completed their fsid change i.e
they have METADATA_UUID incompat flag set, have cleared the
CHANGING_FSID_V2 flag and their fsid/metadata_uuid are different. At
the same time the other half of the disks will have their
fsid/metadata_uuid unchanged and will only have CHANGING_FSID_V2 flag.

This is handled by introducing code in the scan path which:

 a) Handles the case when a device with CHANGING_FSID_V2 flag is
 scanned and as a result btrfs_fs_devices is created with matching
 fsid/metdata_uuid. Subsequently, when a device with completed fsid
 change is scanned it will detect this via the new code in find_fsid
 i.e that such an fs_devices exist that fsid_change flag is set to true,
 it's metadata_uuid/fsid match and the metadata_uuid of the scanned
 device matches that of the fs_devices. In this case, it's important to
 note that the devices which has its fsid change completed will have a
 higher generation number than the device with FSID_CHANGING_V2 flag
 set, so its superblock block will be used during mount. To prevent an
 assertion triggering because the sb used for mounting will have
 differing fsid/metadata_uuid than the ones in the fs_devices struct
 also add code in device_list_add which overwrites the values in
 fs_devices.

 b) Alternatively we can end up with a device that completed its
 fsid change be scanned first which will create the respective
 btrfs_fs_devices struct with differing fsid/metadata_uuid. In this
 case when a device with FSID_CHANGING_V2 flag set is scanned it will
 call the newly added find_fsid_inprogress function which will return
 the correct fs_devices.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2018-12-17 14:51:38 +01:00
arch arch/sh/include/asm/io.h: provide prototypes for PCI I/O mapping in asm/io.h 2018-12-14 15:05:45 -08:00
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fs btrfs: Handle one more split-brain scenario during fsid change 2018-12-17 14:51:38 +01:00
include btrfs: Remove fsid/metadata_fsid fields from btrfs_info 2018-12-17 14:51:37 +01:00
init psi: fix reference to kernel commandline enable 2018-12-14 15:05:45 -08:00
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mm hugetlbfs: call VM_BUG_ON_PAGE earlier in free_huge_page() 2018-12-14 15:05:45 -08:00
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scripts scripts/spdxcheck.py: always open files in binary mode 2018-12-14 15:05:45 -08:00
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Makefile Linux 4.20-rc7 2018-12-16 15:46:55 -08:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.