From b4cdc4260edf7e03d8b6fabb88aec2cdda95917e Mon Sep 17 00:00:00 2001 From: Javier González Date: Mon, 11 Feb 2019 13:25:08 +0100 Subject: lightnvm: pblk: prevent stall due to wb threshold MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit In order to respect mw_cuinits, pblk's write buffer maintains a backpointer to protect data not yet persisted; when writing to the write buffer, this backpointer defines a threshold that pblk's rate-limiter enforces. On small PU configurations, the following scenarios might take place: (i) the threshold is larger than the write buffer and (ii) the threshold is smaller than the write buffer, but larger than the maximun allowed split bio - 256KB at this moment (Note that writes are not always split - we only do this when we the size of the buffer is smaller than the buffer). In both cases, pblk's rate-limiter prevents the I/O to be written to the buffer, thus stalling. This patch fixes the original backpointer implementation by considering the threshold both on buffer creation and on the rate-limiters path, when bio_split is triggered (case (ii) above). Fixes: 766c8ceb16fc ("lightnvm: pblk: guarantee that backpointer is respected on writer stall") Signed-off-by: Javier González Reviewed-by: Hans Holmberg Signed-off-by: Matias Bjørling Signed-off-by: Jens Axboe --- drivers/lightnvm/pblk-rb.c | 25 +++++++++++++++++++------ 1 file changed, 19 insertions(+), 6 deletions(-) (limited to 'drivers/lightnvm/pblk-rb.c') diff --git a/drivers/lightnvm/pblk-rb.c b/drivers/lightnvm/pblk-rb.c index d4ca8c64ee0f..a6133b50ed9c 100644 --- a/drivers/lightnvm/pblk-rb.c +++ b/drivers/lightnvm/pblk-rb.c @@ -45,10 +45,23 @@ void pblk_rb_free(struct pblk_rb *rb) /* * pblk_rb_calculate_size -- calculate the size of the write buffer */ -static unsigned int pblk_rb_calculate_size(unsigned int nr_entries) +static unsigned int pblk_rb_calculate_size(unsigned int nr_entries, + unsigned int threshold) { - /* Alloc a write buffer that can at least fit 128 entries */ - return (1 << max(get_count_order(nr_entries), 7)); + unsigned int thr_sz = 1 << (get_count_order(threshold + NVM_MAX_VLBA)); + unsigned int max_sz = max(thr_sz, nr_entries); + unsigned int max_io; + + /* Alloc a write buffer that can (i) fit at least two split bios + * (considering max I/O size NVM_MAX_VLBA, and (ii) guarantee that the + * threshold will be respected + */ + max_io = (1 << max((int)(get_count_order(max_sz)), + (int)(get_count_order(NVM_MAX_VLBA << 1)))); + if ((threshold + NVM_MAX_VLBA) >= max_io) + max_io <<= 1; + + return max_io; } /* @@ -67,12 +80,12 @@ int pblk_rb_init(struct pblk_rb *rb, unsigned int size, unsigned int threshold, unsigned int alloc_order, order, iter; unsigned int nr_entries; - nr_entries = pblk_rb_calculate_size(size); + nr_entries = pblk_rb_calculate_size(size, threshold); entries = vzalloc(array_size(nr_entries, sizeof(struct pblk_rb_entry))); if (!entries) return -ENOMEM; - power_size = get_count_order(size); + power_size = get_count_order(nr_entries); power_seg_sz = get_count_order(seg_size); down_write(&pblk_rb_lock); @@ -149,7 +162,7 @@ int pblk_rb_init(struct pblk_rb *rb, unsigned int size, unsigned int threshold, * Initialize rate-limiter, which controls access to the write buffer * by user and GC I/O */ - pblk_rl_init(&pblk->rl, rb->nr_entries); + pblk_rl_init(&pblk->rl, rb->nr_entries, threshold); return 0; } -- cgit v1.2.3