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This is the number of concurrent async io requests that
the scan layer will submit to the bcache layer. There
will be an open fd for each of these, so it is best to
keep this well below the default limit for max open files
(1024), otherwise lvm may get EMFILE from open(2) when
there are around 1024 devices to scan on the system.
When lvm2 command is executed in test mode, discard ioctl is skipped.
This may cause even data-loose in case, issuing discard for released
areas was enabled and user 'tested' lvreduce.
udev creates a train wreck of events if we open devices
with RDWR. Until we can fix/disable/scrap udev, work around
this by opening RDONLY and then closing/reopening RDWR when
a write is needed. This invalidates the bcache blocks for
the device before writing so it can trigger unnecessary
rereading.
The md filter can operate in two native modes:
- normal: reads only the start of each device
- full: reads both the start and end of each device
md 1.0 devices place the superblock at the end of the device,
so components of this version will only be identified and
excluded when lvm uses the full md filter.
Previously, the full md filter was only used in commands
that could write to the device. Now, the full md filter
is also applied when there is an md 1.0 device present
on the system. This means the 'pvs' command can avoid
displaying md 1.0 components (at the cost of doubling
the i/o to every device on the system.)
(The md filter can operate in a third mode, using udev,
but this is disabled by default because there have been
problems with reliability of the info returned from udev.)
Remove the io error message from bcache.c since it is not
very useful without the device path.
Make the io error messages from dev_read_bytes/dev_write_bytes
more user friendly.
We have been warning about duplicate devices (and disabling lvmetad)
immediately when the dup was detected (during label_scan). Move the
warnings (and the disabling) to happen later, after label_scan is
finished.
This lets us avoid an unwanted warning message about duplicates
in the special case were md components are eliminated during the
duplicate device resolution.
The device-mapper directory now holds a copy of libdm source. At
the moment this code is identical to libdm. Over time code will
migrate out to appropriate places (see doc/refactoring.txt).
The libdm directory still exists, and contains the source for the
libdevmapper shared library, which we will continue to ship (though
not neccessarily update).
All code using libdm should now use the version in device-mapper.
As we start refactoring the code to break dependencies (see doc/refactoring.txt),
I want us to use full paths in the includes (eg, #include "base/data-struct/list.h").
This makes it more obvious when we're breaking abstraction boundaries, eg, including a file in
metadata/ from base/
md devices using an older superblock version have
superblocks at the end of the md device. For commands
that skip reading the end of devices during filtering,
the md component devs will be scanned, and will appear
as duplicate PVs to the original md device. Remove
these md components from the list of unused duplicate
devices, so they are treated as if they had been
ignored during filtering. This avoids the restrictions
that are placed on using PVs with duplicates.
All these functions are now used as utilities,
e.g. for ioctl (not for io), and need to
open/close the device each time they are called.
(Many of the opens can probably be eliminated by
just using the bcache fd for the ioctl.)
Filters are still applied before any device reading or
the label scan, but any filter checks that want to read
the device are skipped and the device is flagged.
After bcache is populated, but before lvm looks for
devices (i.e. before label scan), the filters are
reapplied to the devices that were flagged above.
The filters will then find the data they need in
bcache.
bcache_invalidate() now returns a bool to indicate success. If fails
if the block is currently held, or the block is dirty and writeback
fails.
Added a bunch of unit tests for the invalidate functions.
Fixed some bugs to do with invalidating errored blocks.
The error handling code wasn't working, but it
appears that just removing it is what we need.
The doesn't really need any different behavior
related to bcache blocks on an io error, it just
wants to know if there was an error.
Create a new dev->bcache_fd that the scanning code owns
and is in charge of opening/closing. This prevents other
parts of lvm code (which do various open/close) from
interfering with the bcache fd. A number of dev_open
and dev_close are removed from the reading path since
the read path now uses the bcache.
With that in place, open(O_EXCL) for pvcreate/pvremove
can then be fixed. That wouldn't work previously because
of other open fds.
New label_scan function populates bcache for each device
on the system.
The two read paths are updated to get data from bcache.
The bcache is not yet used for writing. bcache blocks
for a device are invalidated when the device is written.
With these read errors it's useful to know the reason.
Also avoid to log error just once so we know exactly
how many times we did failing read.
On the other hand reduce repeated log_error() on code 'backtrace'
path and change severity of message to just log_debug() so the
actual read error is printed once for one read.
Actually the removed code is necessary - since not all writes are
getting alligned buffer - older compilers seems to be not able
to create 4K aligned buffers on stack - this the aligning code still
need to be present for write path.
If the data being requested is present in last_[extra_]devbuf,
return that directly instead of reading it from disk again.
Typical LVM2 access patterns request data within two adjacent 4k blocks
so we eliminate some read() system calls by always reading at least 8k.
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.
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.
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 */
- Use 'lvmcache' consistently instead of 'metadata cache'
- Always use 5 characters for source line number
- Remember to convert uuids into printable form
- Use <no name> rather than (null) when VG has no name.
Replaced the confusing device error message "not found (or ignored by
filtering)" by either "not found" or "excluded by a filter".
(Later we should be able to say which filter.)
Left the the liblvm code paths alone.
Older udev versions (udev < v165), don't have the official
udev_device_get_is_initialized function available to query for
device initialization state in udev database. Also, devices don't
have USEC_INITIALIZED udev db variable set - this is bound to the
udev_device_get_is_initialized fn functionality.
In this case, check for "DEVLINKS" variable instead - all block devices
have at least one symlink set for the node (the "/dev/block/<major:minor>".
This symlink is set by default basic udev rules provided by udev directly.
We'll use this as an alternative for the check that initial udev
processing for a device has already finished.
Treat loop device created with 'losetup -P' as regular
partitioned device - so if it has partition table,
prevent its usage in commands like 'pvcreate'.
Before 'pvcreate /dev/loop0' could have erased and formated as PV,
after this patch, device is filtered out and cannot be used.
When not obtaining device from udev, we are doing deep devdir scan,
and at the same time we try to insert everything what /sys/dev/block
knows about. However in case lvm2 is configured to use nonstardard
devdir this way it will see (and scan) devices from a real system.
lvm2 test suite is using its own test devdir with its
own device nodes. To avoid touching real /dev devices, validate
the device node exist in give dir and do not insert such device
into a cache.
With obtain list from udev this patch has no effect
(the normal user path).
We have _insert_dirs() for udev and non-udev compilation.
Compiling without udev missed to call dev_cache_index_devs().
Move the call after _insert_dirs() call so both compilation
gets it.
/sys/dev/block is available since kernel version 2.2.26 (~ 2008):
https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-dev
The VGID/LVID indexing code relies on this feature so skip indexing
if it's not available to avoid error messages about inability to open
/sys/dev/block directory.
We're not going to provide fallback code to read the /sys/block/
instead in this case as that's not that efficient - it needs extra
reads for getting major:minor and reading partitions would also
pose further reads and that's not worth it.
If obtain_device_list_from_udev=0, LVM can make use of persistent .cache
file. This cache file contains only devices which underwent filters in
previous LVM command run. But we need to iterate over all block devices
to create the VGID/LVID index completely for the device mismatch check
to be complete as well.
This patch iterates over block devices found in sysfs to generate the
VGID/LVID index in dev cache if obtain_device_list_from_udev=0
(if obtain_device_list_from_udev=1, we always read complete list of
block devices from udev and we ignore .cache file so we don't need
to look in sysfs for the complete list).
For the case when we print device name associated with struct device
that was not found in /dev, but in sysfs, for example when printing
devices where LV device mismatch is found.
It's correct to have a DM device that has no DM UUID assigned
so no need to issue error message in this case. Also, if the
device doesn't have DM UUID, it's also clear it's not an LVM LV
(...when looking for VGID/LVID while creating VGID/LVID indices
in dev cache).
For example:
$ dmsetup create test --table "0 1 linear /dev/sda 0"
And there's no PV in the system.
Before this patch (spurious error message issued):
$ pvs
_get_sysfs_value: /sys/dev/block/253:2/dm/uuid: no value
With this patch applied (no spurious error message):
$ pvs
If we're using persistent .cache file, we're reading this file instead
of traversing the /dev content. Fix missing indexing by VGID and LVID
here - hook this into persistent_filter_load where we populate device
cache from persistent .cache file instead of scanning /dev.
For example, inducing situation in which we warn about different device
actually used than what LVM thinks should be used based on metadata:
$ lsblk -s /dev/vg/lvol0
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vg-lvol0 253:4 0 124M 0 lvm
`-loop1 7:1 0 128M 0 loop
$ lvmconfig --type diff
global {
use_lvmetad=0
}
devices {
obtain_device_list_from_udev=0
}
(obtain_device_list_from_udev=0 also means the persistent .cache file is used)
Before this patch - pvs is fine as it does the dev scan, but lvs relies
on persistent .cache file and it misses the VGID/LVID indices to check
and warn about incorrect devices used:
$ pvs
Found duplicate PV B9gXTHkIdEIiMVwcOoT2LX3Ywh4YIHgR: using /dev/loop0 not /dev/loop1
Using duplicate PV /dev/loop0 without holders, ignoring /dev/loop1
WARNING: Device mismatch detected for vg/lvol0 which is accessing /dev/loop1 instead of /dev/loop0.
PV VG Fmt Attr PSize PFree
/dev/loop0 vg lvm2 a-- 124.00m 0
$ lvs
Found duplicate PV B9gXTHkIdEIiMVwcOoT2LX3Ywh4YIHgR: using /dev/loop0 not /dev/loop1
Using duplicate PV /dev/loop0 without holders, ignoring /dev/loop1
LV VG Attr LSize
lvol0 vg -wi-a----- 124.00m
With this patch applied - both pvs and lvs is fine - the indices are
always created correctly (lvs just an example here, other LVM commands
that rely on persistent .cache file are fixed with this patch too):
$ pvs
Found duplicate PV B9gXTHkIdEIiMVwcOoT2LX3Ywh4YIHgR: using /dev/loop0 not /dev/loop1
Using duplicate PV /dev/loop0 without holders, ignoring /dev/loop1
WARNING: Device mismatch detected for vg/lvol0 which is accessing /dev/loop1 instead of /dev/loop0.
PV VG Fmt Attr PSize PFree
/dev/loop0 vg lvm2 a-- 124.00m 0
$ lvs
Found duplicate PV B9gXTHkIdEIiMVwcOoT2LX3Ywh4YIHgR: using /dev/loop0 not /dev/loop1
Using duplicate PV /dev/loop0 without holders, ignoring /dev/loop1
WARNING: Device mismatch detected for vg/lvol0 which is accessing /dev/loop1 instead of /dev/loop0.
LV VG Attr LSize
lvol0 vg -wi-a----- 124.00m
It's possible that while a device is already referenced in sysfs, the node
is not yet in /dev directory.
This may happen in some rare cases right after LVs get created - we sync
with udev (or alternatively we create /dev content ourselves) while VG
lock is held. However, dev scan is done without VG lock so devices may
already be in sysfs, but /dev may not be updated yet if we call LVM command
right after LV creation (so the fact that fs_unlock is done within VG
lock is not usable here much). This is not a problem with devtmpfs as
there's at least kernel name for device in /dev as soon as the sysfs
item exists, but we still support environments without devtmpfs or
where different directory for dev nodes is used (e.g. our test suite).
This patch covers these situations by tracking such devices in
_cache.sysfs_only_names helper hash for the vgid/lvid check to work still.
This also resolves commit 6129d2e64d
which was then reverted by commit 109b7e2095
due to performance issues it may have brought (...and it didn't resolve
the problem fully anyway).
