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nbd: clear queue limits on disconnect

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An inactive nbd device may refuse any I/O operations. The nbd_config_put
function calls invalidate_disk, which sets the device capacity to zero
to reject all read and write I/O. For zero-sector flush I/O requests
from blkdev_issue_flush, if the write cache is disabled, the zero-sector
flush I/O immediately returns 0 in submit_bio_noacct. However, since
nbd_config_put does not clear the write cache state, an inactive nbd
device might still have the write cache enabled. In this situation,
zero-sector flush I/O will return -EIO because there is no active socket.
Additionally, BLK_FEAT_FUA and BLK_FEAT_ROTATIONAL flags may also remain
stale, resetting all of them ensures consistent behavior.

The limits update uses queue_limits_commit_update() (the non-freezing
variant) because config_refs == 0 here means every fd is closed and recv
threads have drained, so no in-flight I/O can read q->limits concurrently.

Reviewed-by: Yu Kuai <yukuai@fygo.io>
Signed-off-by: Yang Erkun <yangerkun@huawei.com>
Link: https://patch.msgid.link/20260805122930.57647-4-yangerkun@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Yang Erkun 2026-08-05 20:29:25 +08:00 committed by Jens Axboe
parent 04d8fb23e5
commit 0fdee7c5fa
1 changed files with 26 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

43
drivers/block/nbd.c
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@ -331,6 +331,26 @@ static void nbd_mark_nsock_dead(struct nbd_device *nbd, struct nbd_sock *nsock,
nsock->sent = 0;
}
static void nbd_apply_limits(struct queue_limits *lim, u32 flags)
{
lim->features &= ~(BLK_FEAT_WRITE_CACHE | BLK_FEAT_FUA | BLK_FEAT_ROTATIONAL);
lim->max_hw_discard_sectors = 0;
lim->max_write_zeroes_sectors = 0;
if (flags & NBD_FLAG_SEND_TRIM)
lim->max_hw_discard_sectors = UINT_MAX >> SECTOR_SHIFT;
if (flags & NBD_FLAG_SEND_FLUSH) {
lim->features |= BLK_FEAT_WRITE_CACHE;
if (flags & NBD_FLAG_SEND_FUA)
lim->features |= BLK_FEAT_FUA;
}
if (flags & NBD_FLAG_ROTATIONAL)
lim->features |= BLK_FEAT_ROTATIONAL;
if (flags & NBD_FLAG_SEND_WRITE_ZEROES)
lim->max_write_zeroes_sectors = UINT_MAX >> SECTOR_SHIFT;
}
static int nbd_set_size(struct nbd_device *nbd, loff_t bytesize, loff_t blksize)
{
struct queue_limits lim;
@ -352,23 +372,7 @@ static int nbd_set_size(struct nbd_device *nbd, loff_t bytesize, loff_t blksize)
return 0;
lim = queue_limits_start_update(nbd->disk->queue);
if (nbd->config->flags & NBD_FLAG_SEND_TRIM)
lim.max_hw_discard_sectors = UINT_MAX >> SECTOR_SHIFT;
else
lim.max_hw_discard_sectors = 0;
if (!(nbd->config->flags & NBD_FLAG_SEND_FLUSH)) {
lim.features &= ~(BLK_FEAT_WRITE_CACHE | BLK_FEAT_FUA);
} else if (nbd->config->flags & NBD_FLAG_SEND_FUA) {
lim.features |= BLK_FEAT_WRITE_CACHE | BLK_FEAT_FUA;
} else {
lim.features |= BLK_FEAT_WRITE_CACHE;
lim.features &= ~BLK_FEAT_FUA;
}
if (nbd->config->flags & NBD_FLAG_ROTATIONAL)
lim.features |= BLK_FEAT_ROTATIONAL;
if (nbd->config->flags & NBD_FLAG_SEND_WRITE_ZEROES)
lim.max_write_zeroes_sectors = UINT_MAX >> SECTOR_SHIFT;
nbd_apply_limits(&lim, nbd->config->flags);
lim.logical_block_size = blksize;
lim.physical_block_size = blksize;
error = queue_limits_commit_update_frozen(nbd->disk->queue, &lim);
@ -1469,8 +1473,13 @@ static void nbd_config_put(struct nbd_device *nbd)
if (refcount_dec_and_mutex_lock(&nbd->config_refs,
&nbd->config_lock)) {
struct nbd_config *config = nbd->config;
struct queue_limits lim;
nbd_dev_dbg_close(nbd);
invalidate_disk(nbd->disk);
/* reset queue limits to default */
lim = queue_limits_start_update(nbd->disk->queue);
nbd_apply_limits(&lim, 0);
queue_limits_commit_update(nbd->disk->queue, &lim);
if (nbd->config->bytesize)
kobject_uevent(&nbd_to_dev(nbd)->kobj, KOBJ_CHANGE);
if (test_and_clear_bit(NBD_RT_HAS_PID_FILE,