Reduce system calls

Seems like over the time we have added lots of system calls which are not fully using the device cache or the code is just distrustful too much.

This patch set tries to reduce the number of system calls and should have some positive impact on RHZB 744926.

In my measurements it seems like it's giving extra 10%-30% speedup of processing commands like lvcreate with larger set of devices in system. (depends on the lvm.conf configuration as well.)

!!! NOTICE !!!

It's worth to note that our current code for obtaining device list from udev is upto 80% slower that our normal scan (yep, udev is quite slow and does about ~8 syscalls per device) so unless we try to extend this udev scan with just check only for real PV devices (which has been reject) we have quite noticable speed regression when larger set of devices is present in the system.

Patch set should be back-portable.

Careful review for '*' please.

Zdenek Kabelac (7):
Add common initialization code for struct device
* Add caching of BLKGETSIZE64 ioctl
* Do not drop cache block_size for cached device.
* Do not lstat common path prefix
Minor cleanup of strchr analyzer warning
* Drop extra stat before open of device Skip double stat() call with each _insert

 lib/device/dev-cache.c |  103 +++++++++++++++++++++++++++---------------------
 lib/device/dev-io.c    |   39 +++++++-----------
 lib/device/device.h    |    1 +
 3 files changed, 75 insertions(+), 68 deletions(-)

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1.7.7.3