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Date: Mon, 23 May 2022 10:05:18 +0200 From: Íñigo Huguet <ihuguet@...hat.com> To: Íñigo Huguet <ihuguet@...hat.com>, Edward Cree <ecree.xilinx@...il.com>, bhutchings@...arflare.com, "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org Subject: Re: [PATCH net-next 2/2] sfc: simplify mtd partitions list handling On Fri, May 13, 2022 at 10:02 AM Martin Habets <habetsm.xilinx@...il.com> wrote: > > On Wed, May 11, 2022 at 12:36:04PM +0200, Íñigo Huguet wrote: > > efx_mtd_partitions are embedded inside efx_mcdi_mtd_partition structs. > > They contain a list entry that is appended to efx->mtd_list, which is > > traversed to perform add/remove/rename/etc operations over all > > efx_mtd_partitions. > > > > However, almost all operations done on a efx_mtd_partition asume that it > > is actually embedded inside an efx_mcdi_mtd_partition, and the > > deallocation asume that the first member of the list is located at the > > beginning of the allocated memory. > > > > Given all that asumptions, the possibility of having an > > efx_mtd_partition not embedded in an efx_mcdi_efx_partition doesn't > > exist. Neither it does the possibility of being in a memory position > > other the one allocated for the efx_mcdi_mtd_partition array. Also, they > > never need to be reordered. > > > > Given all that, it is better to get rid of the list and use directly the > > efx_mcdi_mtd_partition array. This shows more clearly how they lay > > in memory, list traversal is more obvious and it save a small amount > > of memory on the list nodes. > > I like this. Just 1 comment below. I will prepare a new version, dropping the previous patch > > > Signed-off-by: Íñigo Huguet <ihuguet@...hat.com> > > --- > > drivers/net/ethernet/sfc/ef10.c | 12 ++++++-- > > drivers/net/ethernet/sfc/efx.h | 4 +-- > > drivers/net/ethernet/sfc/efx_common.c | 3 -- > > drivers/net/ethernet/sfc/mtd.c | 42 ++++++++++----------------- > > drivers/net/ethernet/sfc/net_driver.h | 9 ++++-- > > 5 files changed, 33 insertions(+), 37 deletions(-) > > > > diff --git a/drivers/net/ethernet/sfc/ef10.c b/drivers/net/ethernet/sfc/ef10.c > > index 15a229731296..b5284fa529b7 100644 > > --- a/drivers/net/ethernet/sfc/ef10.c > > +++ b/drivers/net/ethernet/sfc/ef10.c > > @@ -3584,10 +3584,16 @@ static int efx_ef10_mtd_probe(struct efx_nic *efx) > > return 0; > > } > > > > - rc = efx_mtd_add(efx, &parts[0].common, n_parts, sizeof(*parts)); > > -fail: > > + rc = efx_mtd_add(efx, parts, n_parts); > > if (rc) > > - kfree(parts); > > + goto fail; > > + efx->mcdi_mtd_parts = parts; > > + efx->n_mcdi_mtd_parts = n_parts; > > + > > + return 0; > > + > > +fail: > > + kfree(parts); > > return rc; > > } > > > > diff --git a/drivers/net/ethernet/sfc/efx.h b/drivers/net/ethernet/sfc/efx.h > > index c05a83da9e44..2ab9ba691b0d 100644 > > --- a/drivers/net/ethernet/sfc/efx.h > > +++ b/drivers/net/ethernet/sfc/efx.h > > @@ -181,8 +181,8 @@ void efx_update_sw_stats(struct efx_nic *efx, u64 *stats); > > > > /* MTD */ > > #ifdef CONFIG_SFC_MTD > > -int efx_mtd_add(struct efx_nic *efx, struct efx_mtd_partition *parts, > > - size_t n_parts, size_t sizeof_part); > > +int efx_mtd_add(struct efx_nic *efx, struct efx_mcdi_mtd_partition *parts, > > + size_t n_parts); > > static inline int efx_mtd_probe(struct efx_nic *efx) > > { > > return efx->type->mtd_probe(efx); > > diff --git a/drivers/net/ethernet/sfc/efx_common.c b/drivers/net/ethernet/sfc/efx_common.c > > index f6577e74d6e6..8802790403e9 100644 > > --- a/drivers/net/ethernet/sfc/efx_common.c > > +++ b/drivers/net/ethernet/sfc/efx_common.c > > @@ -987,9 +987,6 @@ int efx_init_struct(struct efx_nic *efx, > > INIT_LIST_HEAD(&efx->node); > > INIT_LIST_HEAD(&efx->secondary_list); > > spin_lock_init(&efx->biu_lock); > > -#ifdef CONFIG_SFC_MTD > > - INIT_LIST_HEAD(&efx->mtd_list); > > -#endif > > INIT_WORK(&efx->reset_work, efx_reset_work); > > INIT_DELAYED_WORK(&efx->monitor_work, efx_monitor); > > efx_selftest_async_init(efx); > > diff --git a/drivers/net/ethernet/sfc/mtd.c b/drivers/net/ethernet/sfc/mtd.c > > index 273c08e5455f..4d06e8a9a729 100644 > > --- a/drivers/net/ethernet/sfc/mtd.c > > +++ b/drivers/net/ethernet/sfc/mtd.c > > @@ -12,6 +12,7 @@ > > > > #include "net_driver.h" > > #include "efx.h" > > +#include "mcdi.h" > > > > #define to_efx_mtd_partition(mtd) \ > > container_of(mtd, struct efx_mtd_partition, mtd) > > @@ -48,18 +49,16 @@ static void efx_mtd_remove_partition(struct efx_mtd_partition *part) > > ssleep(1); > > } > > WARN_ON(rc); > > - list_del(&part->node); > > } > > > > -int efx_mtd_add(struct efx_nic *efx, struct efx_mtd_partition *parts, > > - size_t n_parts, size_t sizeof_part) > > +int efx_mtd_add(struct efx_nic *efx, struct efx_mcdi_mtd_partition *parts, > > + size_t n_parts) > > { > > struct efx_mtd_partition *part; > > size_t i; > > > > for (i = 0; i < n_parts; i++) { > > - part = (struct efx_mtd_partition *)((char *)parts + > > - i * sizeof_part); > > + part = &parts[i].common; > > > > part->mtd.writesize = 1; > > > > @@ -78,47 +77,38 @@ int efx_mtd_add(struct efx_nic *efx, struct efx_mtd_partition *parts, > > > > if (mtd_device_register(&part->mtd, NULL, 0)) > > goto fail; > > - > > - /* Add to list in order - efx_mtd_remove() depends on this */ > > - list_add_tail(&part->node, &efx->mtd_list); > > } > > > > return 0; > > > > fail: > > - while (i--) { > > - part = (struct efx_mtd_partition *)((char *)parts + > > - i * sizeof_part); > > - efx_mtd_remove_partition(part); > > - } > > + while (i--) > > + efx_mtd_remove_partition(&parts[i].common); > > + > > /* Failure is unlikely here, but probably means we're out of memory */ > > return -ENOMEM; > > } > > > > void efx_mtd_remove(struct efx_nic *efx) > > { > > - struct efx_mtd_partition *parts, *part, *next; > > + int i; > > > > WARN_ON(efx_dev_registered(efx)); > > > > - if (list_empty(&efx->mtd_list)) > > - return; > > - > > - parts = list_first_entry(&efx->mtd_list, struct efx_mtd_partition, > > - node); > > + for (i = 0; i < efx->n_mcdi_mtd_parts; i++) > > + efx_mtd_remove_partition(&efx->mcdi_mtd_parts[i].common); > > > > - list_for_each_entry_safe(part, next, &efx->mtd_list, node) > > - efx_mtd_remove_partition(part); > > - > > - kfree(parts); > > + kfree(efx->mcdi_mtd_parts); > > + efx->mcdi_mtd_parts = NULL; > > + efx->n_mcdi_mtd_parts = 0; > > It is safer to first set to NULL/0 before freeing the memory. > With this sequence bad things can happen if the thread gets descheduled > right after the kfree. To prevent this we'd also need to use memory barriers. I don't think we need them because all usages of these fields are done under the rtnl lock. I won't apply this change in the new version because I find it useless, but please explain me the reason if you disagree. > > Martin > > > } > > > > void efx_mtd_rename(struct efx_nic *efx) > > { > > - struct efx_mtd_partition *part; > > + int i; > > > > ASSERT_RTNL(); > > > > - list_for_each_entry(part, &efx->mtd_list, node) > > - efx->type->mtd_rename(part); > > + for (i = 0; i < efx->n_mcdi_mtd_parts; i++) > > + efx->type->mtd_rename(&efx->mcdi_mtd_parts[i].common); > > } > > diff --git a/drivers/net/ethernet/sfc/net_driver.h b/drivers/net/ethernet/sfc/net_driver.h > > index 318db906a154..5d20b25b0e82 100644 > > --- a/drivers/net/ethernet/sfc/net_driver.h > > +++ b/drivers/net/ethernet/sfc/net_driver.h > > @@ -107,6 +107,8 @@ struct hwtstamp_config; > > > > struct efx_self_tests; > > > > +struct efx_mcdi_mtd_partition; > > + > > /** > > * struct efx_buffer - A general-purpose DMA buffer > > * @addr: host base address of the buffer > > @@ -865,7 +867,8 @@ enum efx_xdp_tx_queues_mode { > > * @irq_zero_count: Number of legacy IRQs seen with queue flags == 0 > > * @irq_level: IRQ level/index for IRQs not triggered by an event queue > > * @selftest_work: Work item for asynchronous self-test > > - * @mtd_list: List of MTDs attached to the NIC > > + * @mcdi_mtd_parts: Array of MTDs attached to the NIC > > + * @n_mcdi_mtd_parts: Number of MTDs attached to the NIC > > * @nic_data: Hardware dependent state > > * @mcdi: Management-Controller-to-Driver Interface state > > * @mac_lock: MAC access lock. Protects @port_enabled, @phy_mode, > > @@ -1033,7 +1036,8 @@ struct efx_nic { > > struct delayed_work selftest_work; > > > > #ifdef CONFIG_SFC_MTD > > - struct list_head mtd_list; > > + struct efx_mcdi_mtd_partition *mcdi_mtd_parts; > > + unsigned int n_mcdi_mtd_parts; > > #endif > > > > void *nic_data; > > @@ -1134,7 +1138,6 @@ static inline unsigned int efx_port_num(struct efx_nic *efx) > > } > > > > struct efx_mtd_partition { > > - struct list_head node; > > struct mtd_info mtd; > > const char *dev_type_name; > > const char *type_name; > > -- > > 2.34.1 > -- Íñigo Huguet
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