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Callers that read larger amounts of data now get a pointer to read-only
data directly without copying it through an intermediate buffer. This
data is owned by the device layer so the callers no longer free it.
If it obtains the data, it passes it into the supplied callback function
and returns 1. Otherwise the callback receives failed = 1.
Updated config_file_read_fd to use this and similarly return the data
via a callback fn of its own.
Dedicated functions are now used to process each piece of data obtained,
so the refactoring in this file gives us one for the vgsummary and one
for the metadata header. This new type of function takes two parameters
(for now), the obtained data plus a single struct (that must not
reference any data on the stack) that wraps up the entire context needed
to process it.
Rename dev_read() to dev_read_buf() - the function that reads data
into a supplied buffer.
Introduce a new dev_read() that allocates the buffer it returns and
switch the important users over to this. No caller may change the
returned data. (For now, callers are responsible for freeing it after
use, but later the device layer will take full ownership.)
dev_read_buf() should only be used for tiny buffers or unimportant code
(such as the old disk formats).
The creation of wrapped around metadata - where the start of metadata is
written up to the end of the buffer and the remainder follows back at
the start of the buffer - is now restricted to cases where writing the
metadata in one piece wouldn't fit. This shouldn't happen in 'normal'
usage so let's begin treating the code for this as a special case that
can be ignored when optimising 'normal' cases.
If there is sufficient space in the metadata area, align the next
metadata to a disk offset that is a multiple of 4096 bytes and
don't write it circularly. If it doesn't all fit at the end
of the metadata area, go back to the start and write it all there
contiguously.
If there is insufficient space to use the new stricter rules, revert to
the original behaviour, aligning on 512-byte boundaries wrapping around
the circular buffer as required.
Use new ALIGN_ABSOLUTE macro when calculating the start location
of new metadata and adjust the end of buffer detection so that
there is no longer an imposed gap between old and new metadata.
Currently both start and offset should always be divisible by alignment,
so this should have no effect, but a later patch will increase alignment
so these variables can no longer be optimised out.
Expand out the metadata wrapping calculations to prepare
to support a larger alignment.
The current alignment is 512 bytes so
(mdac_area_start + rlocn->offset) % alignment is zero.
Mark the first metadata area on each text format PV as MDA_PRIMARY.
Pass this information down to the device layer so that when
there are two metadata areas on a block device, we can easily
distinguish two independent streams of I/O.
Introduce enum dev_io_reason to categorise block device I/O
in debug messages so it's obvious what it is for.
DEV_IO_SIGNATURES /* Scanning device signatures */
DEV_IO_LABEL /* LVM PV disk label */
DEV_IO_MDA_HEADER /* Text format metadata area header */
DEV_IO_MDA_CONTENT /* Text format metadata area content */
DEV_IO_FMT1 /* Original LVM1 metadata format */
DEV_IO_POOL /* Pool metadata format */
DEV_IO_LV /* Content written to an LV */
DEV_IO_LOG /* Logging messages */
When an ignored metadata area gets flagged for use again, make sure the
code doesn't try to parse its old metadata. Firstly by trying to detect
this situation and skipping the read (while still remembering the
position reached in the circular buffer), and secondly by clearing the
invalid live metadata location on disk as a precaution when subsequently
writing out the precommitted metadata.
Problems showed up when a metadata area in one VG got moved to
another VG in ignored state (still holding metadata for the original
VG) and then later got brought into use in the new VG - only the header
should be read in this case, not any of the metadata content.
vgmerge suffers from a similar problem to the one fixed in commit
8146548d25 ("vgsplit: Fix intermediate
metadata corruption.")
When merging, splitting or renaming VGs, use a new PV status flag
PV_MOVED_VG to mark the PVs that hold metadata with the old VG name and
use this to provide PV-level granularity instead of incorrectly assuming
all PVs in the VG are the same.
Changing the VG of a PV uses the same on-disk mechanism as vgrename.
This relies on recognising both the old and new VG names. Prior to this
patch the vgsplit code incorrectly provided the new VG name twice
instead of the old and new ones. This lead the low-level mechanism not
to recognise the device as already belonging to a VG and so paying no
attention to the location of its existing metadata, sometimes partly
overwriting it and then later trying to read the corrupt metadata and
issuing a checksum error.
lvmcache_foreach_mda() can fail for numerous reasons
and failing error code cannot be ignored (out-of-memory...)
TODO: might need more error handling tunning.
Fix code checking that the 2nd mda which is at the end of disk really
fits the available free space and avoid any DA and MDA interleaving when
we already have DA preallocated. This mainly applies when we're restoring
a PV from VG backup using pvcreate --restorefile where we may already have
some DA preallocated - this means the PV was in a VG before with already
allocated space from it (the LVs were created). Hence we need to avoid
stepping into DA - the MDA can never ever be inside in such case!
The code responsible for this calculation was already in
_text_pv_add_metadata_area fn, but it had a bug in the calculation where
we subtracted one more sector by mistake and then the code could still
incorrectly allocate the MDA inside existing DA. The patch also renames
the variable in the code so it doesn't confuse us in future.
Also, if the 2nd mda doesn't fit, don't silently continue with just 1
MDA (at the start of the disk). If 2nd mda was requested and we can't
create that due to unavailable space, error out correctly (the patch
also adds a test to shell/pvcreate-operation.sh for this case).
In order to reject out of place reshaping with segment data_offset
field on old runtime, add a respective segment type incompatibility
flag causing "+RESHAPE_DATA_OFFSET" to be suffixed to the segment
type name.
Prohibit activation of reshaping RaidLVs on incompatible
lvm2 runtime by storing e.g. 'raid5+RESHAPE' segment type
strings in the lvm2 metadata. Incompatible runtime not
supporting reshaping won't be able to activate those thus
avoiding potential data corruption.
Any new non-reshaping lvconvert command will reset the
segment type string from 'raid5+RESHAPE' to 'raid5'.
See commits
0299a7af1e and
4141409eb0
for segtype flag support.
Since lvmetad is using 'MISSING' in status for 'another' purpose,
we need to support ATM also flag get from this place.
Until fixed better - we accept both flags - alhough lvm2 will
only print in flags.
