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From a3272275156bb9e9533645a44532ed8daadebe03 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@lst.de>
Date: Fri, 27 May 2022 07:58:06 +0200
Subject: [PATCH] block, loop: support partitions without scanning
Historically we did distinguish between a flag that surpressed partition
scanning, and a combinations of the minors variable and another flag if
any partitions were supported. This was generally confusing and doesn't
make much sense, but some corner case uses of the loop driver actually
do want to support manually added partitions on a device that does not
actively scan for partitions. To make things worsee the loop driver
also wants to dynamically toggle the scanning for partitions on a live
gendisk, which makes the disk->flags updates non-atomic.
Introduce a new GD_SUPPRESS_PART_SCAN bit in disk->state that disables
just scanning for partitions, and toggle that instead of GENHD_FL_NO_PART
in the loop driver.
[bva: Notes for this backport:
- drop return code in disk_scan_partitions for GD_SUPPRESS_PART_SCAN.
The check doesn't strictly need ot be in this routine in 5.15, but
this faciliates future changes in this area, since there are
other checks in the same function.
- GD_SUPPRESS_PART_SCAN could go to genh.c, but genhd.c includes
blkdev.h, so we leave the new GD_SUPPRESS_PART_SCAN definition
in the same places as where it was introduced upstream to keep
the changes to a minimum
- upstream commit e16e506ccd673 merges blkdev_reread_part into
disk_scan_partitions. Backporting that change is more churn
than we need, so we also add the check for GD_SUPPRESS_PART_SCAN
into that routine to have the check hit in a 5.15 context.
]
Upstream-Status: Backport [commit b9684a71fca79]
Fixes: 1ebe2e5f9d68 ("block: remove GENHD_FL_EXT_DEVT")
Reported-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20220527055806.1972352-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
---
block/genhd.c | 3 +++
block/ioctl.c | 3 +++
drivers/block/loop.c | 8 ++++----
include/linux/blkdev.h | 1 +
4 files changed, 11 insertions(+), 4 deletions(-)
diff --git a/block/genhd.c b/block/genhd.c
index 4d28f1d5f9b0..0e594c3a8321 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -372,6 +372,9 @@ static void disk_scan_partitions(struct gendisk *disk)
{
struct block_device *bdev;
+ if (test_bit(GD_SUPPRESS_PART_SCAN, &disk->state))
+ return;
+
if (!get_capacity(disk) || !disk_part_scan_enabled(disk))
return;
diff --git a/block/ioctl.c b/block/ioctl.c
index 7a939c178660..bc118f224c00 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -96,6 +96,9 @@ static int blkdev_reread_part(struct block_device *bdev, fmode_t mode)
if (bdev->bd_disk->open_partitions)
return -EBUSY;
+ if (test_bit(GD_SUPPRESS_PART_SCAN, &bdev->bd_disk->state))
+ return -EINVAL;
+
/*
* Reopen the device to revalidate the driver state and force a
* partition rescan.
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 4769caab9ff9..a76302450c46 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1332,7 +1332,7 @@ static int loop_configure(struct loop_device *lo, fmode_t mode,
lo->lo_flags |= LO_FLAGS_PARTSCAN;
partscan = lo->lo_flags & LO_FLAGS_PARTSCAN;
if (partscan)
- lo->lo_disk->flags &= ~GENHD_FL_NO_PART;
+ clear_bit(GD_SUPPRESS_PART_SCAN, &lo->lo_disk->state);
/* enable and uncork uevent now that we are done */
dev_set_uevent_suppress(disk_to_dev(lo->lo_disk), 0);
@@ -1481,7 +1481,7 @@ static int __loop_clr_fd(struct loop_device *lo, bool release)
mutex_lock(&lo->lo_mutex);
lo->lo_flags = 0;
if (!part_shift)
- lo->lo_disk->flags |= GENHD_FL_NO_PART;
+ set_bit(GD_SUPPRESS_PART_SCAN, &lo->lo_disk->state);
lo->lo_state = Lo_unbound;
mutex_unlock(&lo->lo_mutex);
@@ -1598,7 +1598,7 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
if (!err && (lo->lo_flags & LO_FLAGS_PARTSCAN) &&
!(prev_lo_flags & LO_FLAGS_PARTSCAN)) {
- lo->lo_disk->flags &= ~GENHD_FL_NO_PART;
+ clear_bit(GD_SUPPRESS_PART_SCAN, &lo->lo_disk->state);
partscan = true;
}
out_unlock:
@@ -2428,7 +2428,7 @@ static int loop_add(int i)
* userspace tools. Parameters like this in general should be avoided.
*/
if (!part_shift)
- disk->flags |= GENHD_FL_NO_PART;
+ set_bit(GD_SUPPRESS_PART_SCAN, &disk->state);
disk->flags |= GENHD_FL_EXT_DEVT;
atomic_set(&lo->lo_refcnt, 0);
mutex_init(&lo->lo_mutex);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 905844172cfd..15815f1ced9e 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -813,6 +813,7 @@ static inline unsigned int blk_queue_depth(struct request_queue *q)
*/
#define BLK_DEFAULT_SG_TIMEOUT (60 * HZ)
#define BLK_MIN_SG_TIMEOUT (7 * HZ)
+#define GD_SUPPRESS_PART_SCAN 5
struct rq_map_data {
struct page **pages;
--
2.39.2
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