From: Stefan Roesch shr@devkernel.io
mainline inclusion from mainline-v6.2-rc1 commit 8e9d5ead865a1a7af74a444d2f00f1ef4539bfba category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAN96I
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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Patch series "mm/block: add bdi sysfs knobs", v4.
At meta network block devices (nbd) are used to implement remote block storage. In testing and during production it has been observed that these network block devices can consume a huge portion of the dirty writeback cache and writeback can take a considerable time.
To be able to give stricter limits, I'm proposing the following changes:
1) introduce strictlimit knob
Currently the max_ratio knob exists to limit the dirty_memory. However this knob only applies once (dirty_ratio + dirty_background_ratio) / 2 has been reached. With the BDI_CAP_STRICTLIMIT flag, the max_ratio can be applied without reaching that limit. This change exposes that knob.
This knob can also be useful for NFS, fuse filesystems and USB devices.
2) Use part of 1000000 internal calculation
The max_ratio is based on percentage. With the current machine sizes percentage values can be very high (1% of a 256GB main memory is already 2.5GB). This change uses part of 1000000 instead of percentages for the internal calculations.
3) Introduce two new sysfs knobs: min_bytes and max_bytes.
Currently all calculations are based on ratio, but for a user it often more convenient to specify a limit in bytes. The new knobs will not store bytes values, instead they will translate the byte value to a corresponding ratio. As the internal values are now part of 1000, the ratio is closer to the specified value. However the value should be more seen as an approximation as it can fluctuate over time.
3) Introduce two new sysfs knobs: min_ratio_fine and max_ratio_fine.
The granularity for the existing sysfs bdi knobs min_ratio and max_ratio is based on percentage values. The new sysfs bdi knobs min_ratio_fine and max_ratio_fine allow to specify the ratio as part of 1 million.
This patch (of 20):
This adds the bdi_set_strict_limit function to be able to set/unset the BDI_CAP_STRICTLIMIT flag.
Link: https://lkml.kernel.org/r/20221119005215.3052436-1-shr@devkernel.io Link: https://lkml.kernel.org/r/20221119005215.3052436-2-shr@devkernel.io Signed-off-by: Stefan Roesch shr@devkernel.io Cc: Jens Axboe axboe@kernel.dk Cc: Chris Mason clm@meta.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Yifan Qiao qiaoyifan4@huawei.com --- include/linux/backing-dev.h | 1 + mm/page-writeback.c | 15 +++++++++++++++ 2 files changed, 16 insertions(+)
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h index a689a21abe10..c67129defa3a 100644 --- a/include/linux/backing-dev.h +++ b/include/linux/backing-dev.h @@ -106,6 +106,7 @@ static inline unsigned long wb_stat_error(void)
int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio); int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio); +int bdi_set_strict_limit(struct backing_dev_info *bdi, unsigned int strict_limit);
/* * Flags in backing_dev_info::capability diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 0d7cc65c6367..1f6104775a43 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -724,6 +724,21 @@ int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio) } EXPORT_SYMBOL(bdi_set_max_ratio);
+int bdi_set_strict_limit(struct backing_dev_info *bdi, unsigned int strict_limit) +{ + if (strict_limit > 1) + return -EINVAL; + + spin_lock_bh(&bdi_lock); + if (strict_limit) + bdi->capabilities |= BDI_CAP_STRICTLIMIT; + else + bdi->capabilities &= ~BDI_CAP_STRICTLIMIT; + spin_unlock_bh(&bdi_lock); + + return 0; +} + static unsigned long dirty_freerun_ceiling(unsigned long thresh, unsigned long bg_thresh) {