Messages in this thread | | | Date | Fri, 13 Mar 2015 08:55:47 +0900 | From | Minchan Kim <> | Subject | Re: [PATCHv2 7/7] zram: deprecate zram attrs sysfs nodes |
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Hi Sergey,
On Thu, Mar 12, 2015 at 11:47:18PM +0900, Sergey Senozhatsky wrote: > Add Documentation/ABI/obsolete/sysfs-block-zram file and list > obsolete and deprecated attributes there. The patch also adds > additional information to zram documentation and describes the > basic strategy: > - the existing RW nodes will be downgraded to WO nodes (in 4.11) > - deprecated RO sysfs nodes will eventually be removed (in 4.11) > > Users will be additionally notified about deprecated attr usage > by pr_warn_once() (added to every deprecated attr _show()), as > suggested by Minchan Kim. > > Example: > zram: Attribute mem_used_max will be removed. See zram documentation. > > User space is advised to use zram<id>/stat, zram<id>/io_stat and > zram<id>/mm_stat files. > > Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> > --- > Documentation/ABI/obsolete/sysfs-block-zram | 119 ++++++++++++++++++++++++++++ > Documentation/blockdev/zram.txt | 16 ++++ > drivers/block/zram/zram_drv.c | 12 +++ > 3 files changed, 147 insertions(+) > create mode 100644 Documentation/ABI/obsolete/sysfs-block-zram > > diff --git a/Documentation/ABI/obsolete/sysfs-block-zram b/Documentation/ABI/obsolete/sysfs-block-zram > new file mode 100644 > index 0000000..720ea92 > --- /dev/null > +++ b/Documentation/ABI/obsolete/sysfs-block-zram > @@ -0,0 +1,119 @@ > +What: /sys/block/zram<id>/num_reads > +Date: August 2015 > +Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> > +Description: > + The num_reads file is read-only and specifies the number of > + reads (failed or successful) done on this device. > + Now accessible via zram<id>/stat node. > + > +What: /sys/block/zram<id>/num_writes > +Date: August 2015 > +Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> > +Description: > + The num_writes file is read-only and specifies the number of > + writes (failed or successful) done on this device. > + Now accessible via zram<id>/stat node. > + > +What: /sys/block/zram<id>/invalid_io > +Date: August 2015 > +Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> > +Description: > + The invalid_io file is read-only and specifies the number of > + non-page-size-aligned I/O requests issued to this device. > + Now accessible via zram<id>/io_stat node. > + > +What: /sys/block/zram<id>/failed_reads > +Date: August 2015 > +Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> > +Description: > + The failed_reads file is read-only and specifies the number of > + failed reads happened on this device. > + Now accessible via zram<id>/io_stat node. > + > +What: /sys/block/zram<id>/failed_writes > +Date: August 2015 > +Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> > +Description: > + The failed_writes file is read-only and specifies the number of > + failed writes happened on this device. > + Now accessible via zram<id>/io_stat node. > + > +What: /sys/block/zram<id>/notify_free > +Date: August 2015 > +Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> > +Description: > + The notify_free file is read-only. Depending on device usage > + scenario it may account a) the number of pages freed because > + of swap slot free notifications or b) the number of pages freed > + because of REQ_DISCARD requests sent by bio. The former ones > + are sent to a swap block device when a swap slot is freed, which > + implies that this disk is being used as a swap disk. The latter > + ones are sent by filesystem mounted with discard option, > + whenever some data blocks are getting discarded. > + Now accessible via zram<id>/io_stat node. > + > +What: /sys/block/zram<id>/zero_pages > +Date: August 2015 > +Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> > +Description: > + The zero_pages file is read-only and specifies number of zero > + filled pages written to this disk. No memory is allocated for > + such pages. > + Now accessible via zram<id>/mm_stat node. > + > +What: /sys/block/zram<id>/orig_data_size > +Date: August 2015 > +Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> > +Description: > + The orig_data_size file is read-only and specifies uncompressed > + size of data stored in this disk. This excludes zero-filled > + pages (zero_pages) since no memory is allocated for them. > + Unit: bytes > + Now accessible via zram<id>/mm_stat node. > + > +What: /sys/block/zram<id>/compr_data_size > +Date: August 2015 > +Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> > +Description: > + The compr_data_size file is read-only and specifies compressed > + size of data stored in this disk. So, compression ratio can be > + calculated using orig_data_size and this statistic. > + Unit: bytes > + Now accessible via zram<id>/mm_stat node. > + > +What: /sys/block/zram<id>/mem_used_total > +Date: August 2015 > +Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> > +Description: > + The mem_used_total file is read-only and specifies the amount > + of memory, including allocator fragmentation and metadata > + overhead, allocated for this disk. So, allocator space > + efficiency can be calculated using compr_data_size and this > + statistic. > + Unit: bytes > + Now accessible via zram<id>/mm_stat node. > + > +What: /sys/block/zram<id>/mem_used_max > +Date: August 2015 > +Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> > +Description: > + The mem_used_max file is read/write and specifies the amount > + of maximum memory zram have consumed to store compressed data. > + For resetting the value, you should write "0". Otherwise, > + you could see -EINVAL. > + Unit: bytes > + Downgraded to write-only node: so it's possible to set new > + value only; its current value is stored in zram<id>/mm_stat > + node. > + > +What: /sys/block/zram<id>/mem_limit > +Date: August 2015 > +Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> > +Description: > + The mem_limit file is read/write and specifies the maximum > + amount of memory ZRAM can use to store the compressed data. > + The limit could be changed in run time and "0" means disable > + the limit. No limit is the initial state. Unit: bytes > + Downgraded to write-only node: so it's possible to set new > + value only; its current value is stored in zram<id>/mm_stat > + node. > diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt > index b133138..44b1a77 100644 > --- a/Documentation/blockdev/zram.txt > +++ b/Documentation/blockdev/zram.txt > @@ -148,6 +148,22 @@ num_migrated RO the number of objects migrated migrated by compaction > compact WO trigger memory compaction > > > +WARNING > +======= > +per-stat sysfs attributes are considered to be deprecated. > +The basic strategy is: > +-- the existing RW nodes will be downgraded to WO nodes (in linux 4.11) > +-- deprecated RO sysfs nodes will eventually be removed (in linux 4.11) > + > +The list of deprecated attributes can be found here: > +Documentation/ABI/obsolete/sysfs-block-zram > + > +Basically, every attribute that has its own read accessible sysfs node > +(e.g. num_reads) *AND* is accessible via one of the stat files (zram<id>/stat > +or zram<id>/io_stat or zram<id>/mm_stat) is considered to be deprecated. > + > +User space is advised to use the following files to read the device statistics. > + > File /sys/block/zram<id>/stat > > Represents block layer statistics. Read Documentation/block/stat.txt for > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c > index 7493096..2aced91 100644 > --- a/drivers/block/zram/zram_drv.c > +++ b/drivers/block/zram/zram_drv.c > @@ -47,11 +47,19 @@ static const char *default_compressor = "lzo"; > /* Module params (documentation at end) */ > static unsigned int num_devices = 1; > > +static inline void deprecated_attr_warn(const char *name) > +{ > + pr_warn_once("Attribute %s will be removed. See zram documentation.\n", > + name);
How about adding pid, comm? Admin can know which process touches.
> +} > + > #define ZRAM_ATTR_RO(name) \ > static ssize_t name##_show(struct device *d, \ > struct device_attribute *attr, char *b) \ > { \ > struct zram *zram = dev_to_zram(d); \ > + \ > + deprecated_attr_warn(__stringify(name)); \
It just reports once for first-touched stat and miss other stats by ZRAM_ATTR_RO. Of course, you warned "See zram documentation" so he might know about other stats plan, too. If it's your intention, let's make warn more clear.
"Atrribute $s will be removed. Also, there are other stats we will remove in future. See Documentation/blockdev/zram.txt"
> return scnprintf(b, PAGE_SIZE, "%llu\n", \ > (u64)atomic64_read(&zram->stats.name)); \ > } \ > @@ -206,6 +214,7 @@ static ssize_t orig_data_size_show(struct device *dev, > { > struct zram *zram = dev_to_zram(dev); > > + deprecated_attr_warn("orig_data_size"); > return scnprintf(buf, PAGE_SIZE, "%llu\n", > (u64)(atomic64_read(&zram->stats.pages_stored)) << PAGE_SHIFT); > } > @@ -216,6 +225,7 @@ static ssize_t mem_used_total_show(struct device *dev, > u64 val = 0; > struct zram *zram = dev_to_zram(dev); > > + deprecated_attr_warn("mem_used_total"); > down_read(&zram->init_lock); > if (init_done(zram)) { > struct zram_meta *meta = zram->meta; > @@ -245,6 +255,7 @@ static ssize_t mem_limit_show(struct device *dev, > u64 val; > struct zram *zram = dev_to_zram(dev); > > + deprecated_attr_warn("mem_limit"); > down_read(&zram->init_lock); > val = zram->limit_pages; > up_read(&zram->init_lock); > @@ -276,6 +287,7 @@ static ssize_t mem_used_max_show(struct device *dev, > u64 val = 0; > struct zram *zram = dev_to_zram(dev); > > + deprecated_attr_warn("mem_used_max"); > down_read(&zram->init_lock); > if (init_done(zram)) > val = atomic_long_read(&zram->stats.max_used_pages); > -- > 2.3.2.209.gd67f9d5 >
-- Kind regards, Minchan Kim
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