Hi!
If an implementation does happen to have it set, we would happily read it in as the next block to write to for writes. Since a high bit is set, it pushes the block number out of the range of an 'arena', and we fail such a write with an EIO.
Follow the robustness principle, and tolerate such implementations by stripping out the zero flag when populating the free list during initialization. Additionally, use the same stripped out entries for detection of incomplete writes and map restoration that happens at this stage.
Add a sysfs file 'log_zero_flags' that indicates the ability to accept such a layout to userspace applications. This enables 'ndctl check-namespace' to recognize whether the kernel is able to handle zero flags, or whether it should attempt a fix-up under the --repair option.
Ok, so new /sys file is added; but that should have entry in Documentation/ and that one is not there AFAICT. (Not in -linus, so I assume not in -stable, either).
Best regards, Pavel
Cc: Dan Williams dan.j.williams@intel.com Reported-by: Dexuan Cui decui@microsoft.com Reported-by: Pedro d'Aquino Filocre F S Barbuda pbarbuda@microsoft.com Tested-by: Dexuan Cui decui@microsoft.com Signed-off-by: Vishal Verma vishal.l.verma@intel.com Signed-off-by: Dan Williams dan.j.williams@intel.com Signed-off-by: Sasha Levin sashal@kernel.org
drivers/nvdimm/btt.c | 25 +++++++++++++++++++------ drivers/nvdimm/btt.h | 2 ++ drivers/nvdimm/btt_devs.c | 8 ++++++++ 3 files changed, 29 insertions(+), 6 deletions(-)
diff --git a/drivers/nvdimm/btt.c b/drivers/nvdimm/btt.c index d78cfe82ad5c..1064a703ccec 100644 --- a/drivers/nvdimm/btt.c +++ b/drivers/nvdimm/btt.c @@ -542,8 +542,8 @@ static int arena_clear_freelist_error(struct arena_info *arena, u32 lane) static int btt_freelist_init(struct arena_info *arena) { int new, ret;
- u32 i, map_entry; struct log_entry log_new;
- u32 i, map_entry, log_oldmap, log_newmap;
arena->freelist = kcalloc(arena->nfree, sizeof(struct free_entry), GFP_KERNEL); @@ -555,16 +555,22 @@ static int btt_freelist_init(struct arena_info *arena) if (new < 0) return new;
/* old and new map entries with any flags stripped out */log_oldmap = ent_lba(le32_to_cpu(log_new.old_map));log_newmap = ent_lba(le32_to_cpu(log_new.new_map));- /* sub points to the next one to be overwritten */ arena->freelist[i].sub = 1 - new; arena->freelist[i].seq = nd_inc_seq(le32_to_cpu(log_new.seq));
arena->freelist[i].block = le32_to_cpu(log_new.old_map);
arena->freelist[i].block = log_oldmap;/* * FIXME: if error clearing fails during init, we want to make * the BTT read-only */
if (ent_e_flag(log_new.old_map)) {
if (ent_e_flag(log_new.old_map) &&!ent_normal(log_new.old_map)) {arena->freelist[i].has_err = 1; ret = arena_clear_freelist_error(arena, i); if (ret) dev_err_ratelimited(to_dev(arena),@@ -572,7 +578,7 @@ static int btt_freelist_init(struct arena_info *arena) } /* This implies a newly created or untouched flog entry */
if (log_new.old_map == log_new.new_map)
if (log_oldmap == log_newmap) continue;/* Check if map recovery is needed */ @@ -580,8 +586,15 @@ static int btt_freelist_init(struct arena_info *arena) NULL, NULL, 0); if (ret) return ret;
if ((le32_to_cpu(log_new.new_map) != map_entry) &&(le32_to_cpu(log_new.old_map) == map_entry)) {
/** The map_entry from btt_read_map is stripped of any flag bits,* so use the stripped out versions from the log as well for* testing whether recovery is needed. For restoration, use the* 'raw' version of the log entries as that captured what we* were going to write originally.*/if ((log_newmap != map_entry) && (log_oldmap == map_entry)) { /* * Last transaction wrote the flog, but wasn't able * to complete the map write. So fix up the map.diff --git a/drivers/nvdimm/btt.h b/drivers/nvdimm/btt.h index db3cb6d4d0d4..ddff49c707b0 100644 --- a/drivers/nvdimm/btt.h +++ b/drivers/nvdimm/btt.h @@ -44,6 +44,8 @@ #define ent_e_flag(ent) (!!(ent & MAP_ERR_MASK)) #define ent_z_flag(ent) (!!(ent & MAP_TRIM_MASK)) #define set_e_flag(ent) (ent |= MAP_ERR_MASK) +/* 'normal' is both e and z flags set */ +#define ent_normal(ent) (ent_e_flag(ent) && ent_z_flag(ent)) enum btt_init_state { INIT_UNCHECKED = 0, diff --git a/drivers/nvdimm/btt_devs.c b/drivers/nvdimm/btt_devs.c index e341498876ca..9486acc08402 100644 --- a/drivers/nvdimm/btt_devs.c +++ b/drivers/nvdimm/btt_devs.c @@ -159,11 +159,19 @@ static ssize_t size_show(struct device *dev, } static DEVICE_ATTR_RO(size); +static ssize_t log_zero_flags_show(struct device *dev,
struct device_attribute *attr, char *buf)+{
- return sprintf(buf, "Y\n");
+} +static DEVICE_ATTR_RO(log_zero_flags);
static struct attribute *nd_btt_attributes[] = { &dev_attr_sector_size.attr, &dev_attr_namespace.attr, &dev_attr_uuid.attr, &dev_attr_size.attr,
- &dev_attr_log_zero_flags.attr, NULL,
};