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fs/quota: handle overflows of sysctl fs.quota.* and report as unsigned long 

Quota statistics counted as 64-bit per-cpu counter. Reading sums per-cpu
fractions as signed 64-bit int, filters negative values and then reports
lower half as signed 32-bit int.

Result may looks like:

fs.quota.allocated_dquots = 22327
fs.quota.cache_hits = -489852115
fs.quota.drops = -487288718
fs.quota.free_dquots = 22083
fs.quota.lookups = -486883485
fs.quota.reads = 22327
fs.quota.syncs = 335064
fs.quota.writes = 3088689

Values bigger than 2^31-1 reported as negative.

All counters except "allocated_dquots" and "free_dquots" are monotonic,
thus they should be reported as is without filtering negative values.

Kernel doesn't have generic helper for 64-bit sysctl yet,
let's use at least unsigned long.

Link: https://lore.kernel.org/r/157337934693.2078.9842146413181153727.stgit@buzz
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Jan Kara <jack@suse.cz>
This commit is contained in:
Konstantin Khlebnikov 2019-11-10 12:49:06 +03:00 committed by Jan Kara
parent 355b9aae86
commit 6fcbcec9cf
2 changed files with 18 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
fs/quota/dquot.c
View File

@ -2848,68 +2848,73 @@ EXPORT_SYMBOL(dquot_quotactl_sysfile_ops);
static int do_proc_dqstats(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
unsigned int type = (int *)table->data - dqstats.stat;
unsigned int type = (unsigned long *)table->data - dqstats.stat;
s64 value = percpu_counter_sum(&dqstats.counter[type]);
/* Filter negative values for non-monotonic counters */
if (value < 0 && (type == DQST_ALLOC_DQUOTS ||
type == DQST_FREE_DQUOTS))
value = 0;
/* Update global table */
dqstats.stat[type] =
percpu_counter_sum_positive(&dqstats.counter[type]);
return proc_dointvec(table, write, buffer, lenp, ppos);
dqstats.stat[type] = value;
return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
}
static struct ctl_table fs_dqstats_table[] = {
{
.procname = "lookups",
.data = &dqstats.stat[DQST_LOOKUPS],
.maxlen = sizeof(int),
.maxlen = sizeof(unsigned long),
.mode = 0444,
.proc_handler = do_proc_dqstats,
},
{
.procname = "drops",
.data = &dqstats.stat[DQST_DROPS],
.maxlen = sizeof(int),
.maxlen = sizeof(unsigned long),
.mode = 0444,
.proc_handler = do_proc_dqstats,
},
{
.procname = "reads",
.data = &dqstats.stat[DQST_READS],
.maxlen = sizeof(int),
.maxlen = sizeof(unsigned long),
.mode = 0444,
.proc_handler = do_proc_dqstats,
},
{
.procname = "writes",
.data = &dqstats.stat[DQST_WRITES],
.maxlen = sizeof(int),
.maxlen = sizeof(unsigned long),
.mode = 0444,
.proc_handler = do_proc_dqstats,
},
{
.procname = "cache_hits",
.data = &dqstats.stat[DQST_CACHE_HITS],
.maxlen = sizeof(int),
.maxlen = sizeof(unsigned long),
.mode = 0444,
.proc_handler = do_proc_dqstats,
},
{
.procname = "allocated_dquots",
.data = &dqstats.stat[DQST_ALLOC_DQUOTS],
.maxlen = sizeof(int),
.maxlen = sizeof(unsigned long),
.mode = 0444,
.proc_handler = do_proc_dqstats,
},
{
.procname = "free_dquots",
.data = &dqstats.stat[DQST_FREE_DQUOTS],
.maxlen = sizeof(int),
.maxlen = sizeof(unsigned long),
.mode = 0444,
.proc_handler = do_proc_dqstats,
},
{
.procname = "syncs",
.data = &dqstats.stat[DQST_SYNCS],
.maxlen = sizeof(int),
.maxlen = sizeof(unsigned long),
.mode = 0444,
.proc_handler = do_proc_dqstats,
},

2
include/linux/quota.h
View File

@ -263,7 +263,7 @@ enum {
};
struct dqstats {
int stat[_DQST_DQSTAT_LAST];
unsigned long stat[_DQST_DQSTAT_LAST];
struct percpu_counter counter[_DQST_DQSTAT_LAST];
};