102 lines
3.6 KiB
Diff
102 lines
3.6 KiB
Diff
From 3117c3f45edbcc269baaebd3d13f39b7bf884aa6 Mon Sep 17 00:00:00 2001
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From: Evan Green <evgreen@chromium.org>
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Date: Thu, 14 Nov 2019 15:50:08 -0800
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Subject: loop: Better discard support for block devices
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If the backing device for a loop device is itself a block device,
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then mirror the "write zeroes" capabilities of the underlying
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block device into the loop device. Copy this capability into both
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max_write_zeroes_sectors and max_discard_sectors of the loop device.
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The reason for this is that REQ_OP_DISCARD on a loop device translates
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into blkdev_issue_zeroout(), rather than blkdev_issue_discard(). This
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presents a consistent interface for loop devices (that discarded data
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is zeroed), regardless of the backing device type of the loop device.
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There should be no behavior change for loop devices backed by regular
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files.
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This change fixes blktest block/003, and removes an extraneous
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error print in block/013 when testing on a loop device backed
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by a block device that does not support discard.
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Signed-off-by: Evan Green <evgreen@chromium.org>
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Reviewed-by: Gwendal Grignou <gwendal@chromium.org>
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Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
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---
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drivers/block/loop.c | 40 +++++++++++++++++++++++++++++-----------
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1 file changed, 29 insertions(+), 11 deletions(-)
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--- a/drivers/block/loop.c
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+++ b/drivers/block/loop.c
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@@ -427,11 +427,12 @@ static int lo_fallocate(struct loop_devi
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* information.
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*/
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struct file *file = lo->lo_backing_file;
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+ struct request_queue *q = lo->lo_queue;
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int ret;
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mode |= FALLOC_FL_KEEP_SIZE;
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- if ((!file->f_op->fallocate) || lo->lo_encrypt_key_size) {
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+ if (!blk_queue_discard(q)) {
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ret = -EOPNOTSUPP;
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goto out;
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}
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@@ -862,6 +863,21 @@ static void loop_config_discard(struct l
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struct file *file = lo->lo_backing_file;
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struct inode *inode = file->f_mapping->host;
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struct request_queue *q = lo->lo_queue;
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+ struct request_queue *backingq;
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+
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+ /*
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+ * If the backing device is a block device, mirror its zeroing
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+ * capability. REQ_OP_DISCARD translates to a zero-out even when backed
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+ * by block devices to keep consistent behavior with file-backed loop
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+ * devices.
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+ */
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+ if (S_ISBLK(inode->i_mode) && !lo->lo_encrypt_key_size) {
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+ backingq = bdev_get_queue(inode->i_bdev);
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+ blk_queue_max_discard_sectors(q,
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+ backingq->limits.max_write_zeroes_sectors);
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+
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+ blk_queue_max_write_zeroes_sectors(q,
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+ backingq->limits.max_write_zeroes_sectors);
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/*
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* We use punch hole to reclaim the free space used by the
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@@ -869,22 +885,24 @@ static void loop_config_discard(struct l
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* encryption is enabled, because it may give an attacker
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* useful information.
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*/
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- if ((!file->f_op->fallocate) ||
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- lo->lo_encrypt_key_size) {
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+ } else if ((!file->f_op->fallocate) || lo->lo_encrypt_key_size) {
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q->limits.discard_granularity = 0;
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q->limits.discard_alignment = 0;
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blk_queue_max_discard_sectors(q, 0);
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blk_queue_max_write_zeroes_sectors(q, 0);
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- blk_queue_flag_clear(QUEUE_FLAG_DISCARD, q);
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- return;
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- }
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- q->limits.discard_granularity = inode->i_sb->s_blocksize;
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- q->limits.discard_alignment = 0;
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+ } else {
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+ q->limits.discard_granularity = inode->i_sb->s_blocksize;
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+ q->limits.discard_alignment = 0;
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- blk_queue_max_discard_sectors(q, UINT_MAX >> 9);
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- blk_queue_max_write_zeroes_sectors(q, UINT_MAX >> 9);
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- blk_queue_flag_set(QUEUE_FLAG_DISCARD, q);
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+ blk_queue_max_discard_sectors(q, UINT_MAX >> 9);
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+ blk_queue_max_write_zeroes_sectors(q, UINT_MAX >> 9);
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+ }
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+
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+ if (q->limits.max_write_zeroes_sectors)
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+ blk_queue_flag_set(QUEUE_FLAG_DISCARD, q);
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+ else
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+ blk_queue_flag_clear(QUEUE_FLAG_DISCARD, q);
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}
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static void loop_unprepare_queue(struct loop_device *lo)
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