Hello developers,
I'm currently trying to implement a new method for managing inode and
entry modifications that will be faster (I hope) than the current method
for the most common cases. To do so I need to know exactly how the
locking mechanism works. I have been browsing the source code and doing
some tests, and I would like to be sure that I have understood it
correctly before continuing.
All information is based on latest qa releases from 3.3 branch.
My understanding is this:
- There are three locking fops: lk, inodelk and entrylk.
- Client application locks created using fcntl() are received by the
translators as lk requests.
- All other functionalities of lk fop are not currently used by any
translator (I mean F_RESLK_LCK, F_RESLK_LCKW, F_RESLK_UNLCK and F_GETLK_FD).
- inodelk and entrlylk are only used by AFR to lock inodes or directory
entries before modification.
- Translators don't generate lk requests internally.
- Client application requests cannot directly generate an inodelk or
entrylk requests.
- inodelk and entrylk locks are always mandatory.
- lk locks may be mandatory or advisory.
- lk and inodelk are independent from each other, meaning that a lock
using lk will not be visible to inodelk and will not block it. inodelk
won't block lk requests neither.
- User requests can only be blocked by lk created locks (if a write
request from user is allowed to pass without using inodelk, it won't be
blocked by a previous inodelk).
Is this interpretation correct and complete ?
Thanks for your help,
Xavi
