> On 4 Aug 2018, at 20.35, Matias Bjørling <mb@xxxxxxxxxxx> wrote: > >> On 08/03/2018 03:30 PM, Javier González wrote: >> # Changes singe V1: >> - Fix double I/O on the read path (by Matias) >> - Improve commit message (by Jens) >> pblk guarantees write ordering at a chunk level through a per open chunk >> semaphore. At this point, since we only have an open I/O stream for both >> user and GC data, the semaphore is per parallel unit. >> Since metadata I/O is synchronous, the semaphore is not needed as >> ordering is guaranteed. However, if the metadata scheme changes or >> multiple streams are open, this guarantee might not be preserved. >> This patch makes sure that all writes go through the semaphore, even for >> synchronous I/O. This is consistent with pblk's write I/O model. It also >> simplifies maintenance since changes in the metdatada scheme could cause >> ordering issues. >> Signed-off-by: Javier González <javier@xxxxxxxxxxxx> >> --- >> drivers/lightnvm/pblk-core.c | 18 ++++++++++++++++-- >> drivers/lightnvm/pblk.h | 1 + >> 2 files changed, 17 insertions(+), 2 deletions(-) >> diff --git a/drivers/lightnvm/pblk-core.c b/drivers/lightnvm/pblk-core.c >> index 00984b486fea..6432faf5b19c 100644 >> --- a/drivers/lightnvm/pblk-core.c >> +++ b/drivers/lightnvm/pblk-core.c >> @@ -493,6 +493,20 @@ int pblk_submit_io_sync(struct pblk *pblk, struct nvm_rq *rqd) >> return nvm_submit_io_sync(dev, rqd); >> } >> +int pblk_submit_io_sync_sem(struct pblk *pblk, struct nvm_rq *rqd) > > Nitpicking a bit. It looks to me that a function that has semaphore in its name, should take the semaphore in all cases unless it returns an error. When it only does it on writes, it creates confusion. > > Maybe this would be one of the cases where it is okay to have the logic it in the caller function, or do such that it takes a flag if it should take the semaphore. That'll make it explicit when it is done. I think it’s cleaner to make a helper as the pattern repeats on all write sync I/Os. I’m ok with moving the check to the caller and only using this helper on the write path. I can send a V3 next week. Javier.
