lightnvm: pblk: fail gracefully on irrec. error

Due to user writes being decoupled from media writes because of the need
of an intermediate write buffer, irrecoverable media write errors lead
to pblk stalling; user writes fill up the buffer and end up in an
infinite retry loop.

In order to let user writes fail gracefully, it is necessary for pblk to
keep track of its own internal state and prevent further writes from
being placed into the write buffer.

This patch implements a state machine to keep track of internal errors
and, in case of failure, fail further user writes in an standard way.
Depending on the type of error, pblk will do its best to persist
buffered writes (which are already acknowledged) and close down on a
graceful manner. This way, data might be recovered by re-instantiating
pblk. Such state machine paves out the way for a state-based FTL log.

Signed-off-by: Javier González <javier@cnexlabs.com>
Signed-off-by: Matias Bjørling <matias@cnexlabs.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/lightnvm/pblk-read.c b/drivers/lightnvm/pblk-read.c
index 36726462913f..ed2ea01a0a38 100644
--- a/drivers/lightnvm/pblk-read.c
+++ b/drivers/lightnvm/pblk-read.c
@@ -142,6 +142,7 @@ static void pblk_end_io_read(struct nvm_rq *rqd)
 #endif
 
 	pblk_free_rqd(pblk, rqd, READ);
+	atomic_dec(&pblk->inflight_io);
 }
 
 static int pblk_fill_partial_read_bio(struct pblk *pblk, struct nvm_rq *rqd,
@@ -347,6 +348,7 @@ int pblk_submit_read(struct pblk *pblk, struct bio *bio)
 	bio_get(bio);
 	if (bitmap_full(&read_bitmap, nr_secs)) {
 		bio_endio(bio);
+		atomic_inc(&pblk->inflight_io);
 		pblk_end_io_read(rqd);
 		return NVM_IO_OK;
 	}
@@ -516,6 +518,7 @@ int pblk_submit_read_gc(struct pblk *pblk, u64 *lba_list, void *data,
 				msecs_to_jiffies(PBLK_COMMAND_TIMEOUT_MS))) {
 		pr_err("pblk: GC read I/O timed out\n");
 	}
+	atomic_dec(&pblk->inflight_io);
 
 	if (rqd.error) {
 		atomic_long_inc(&pblk->read_failed_gc);