| Message ID | 20220103190342.146980-1-hch@lst.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | block: deprecate autoloading based on dev_t | expand |
On 2022/01/04 4:03, Christoph Hellwig wrote: > Make the legacy dev_t based autoloading optional and add a deprecation > warning. This kind of autoloading has ceased to be useful about 20 years > ago. This is good for locking dependency simplification. But > > Signed-off-by: Christoph Hellwig <hch@lst.de> > --- > block/Kconfig | 11 +++++++++++ > block/bdev.c | 9 ++++++--- > block/genhd.c | 6 ++++++ > 3 files changed, 23 insertions(+), 3 deletions(-) > > diff --git a/block/Kconfig b/block/Kconfig > index d5d4197b7ed2d..9cd8706faa7be 100644 > --- a/block/Kconfig > +++ b/block/Kconfig > @@ -26,6 +26,17 @@ menuconfig BLOCK > > if BLOCK > > +config BLOCK_LEGACY_AUTOLOAD > + bool "Legacy autoloading support" > + help > + Enable loading modules and creating block device instances based on > + accesses through their device special file. This is a historic Linux > + feature and makes no sense in a udev world where device files are > + created on demand. > + > + Say N here unless your boot broke without it, in which case you should > + send a report to linux-block@vger.kernel.org and your distribution. I don't think the affected scope is limited to the boot process. This change affects userspace programs which do not run in the boot process. A program which do not use ioctl(LOOP_CTL_GET_FREE) would be possible. Current: ---------- root@fuzz:~# ls -l /dev/loop* crw-rw---- 1 root disk 10, 237 Jan 4 09:29 /dev/loop-control root@fuzz:~# mknod /dev/loop0 b 7 0 root@fuzz:~# cat /dev/loop0 root@fuzz:~# echo $? 0 ---------- With CONFIG_BLOCK_LEGACY_AUTOLOAD=n: ---------- root@fuzz:~# ls -l /dev/loop* crw-rw---- 1 root disk 10, 237 Jan 4 09:33 /dev/loop-control root@fuzz:~# mknod /dev/loop0 b 7 0 root@fuzz:~# cat /dev/loop0 cat: /dev/loop0: No such device or address root@fuzz:~# echo $? 1 root@fuzz:~# losetup /dev/loop0 testfile losetup: /dev/loop0: failed to set up loop device: No such device or address ---------- > + > config BLK_RQ_ALLOC_TIME > bool > > diff --git a/block/bdev.c b/block/bdev.c > index 8bf93a19041b7..dd6fd5b807b30 100644 > --- a/block/bdev.c > +++ b/block/bdev.c > @@ -738,12 +738,15 @@ struct block_device *blkdev_get_no_open(dev_t dev) > struct inode *inode; > > inode = ilookup(blockdev_superblock, dev); > - if (!inode) { > + if (!inode && IS_ENABLED(CONFIG_BLOCK_LEGACY_AUTOLOAD)) { > blk_request_module(dev); > inode = ilookup(blockdev_superblock, dev); > - if (!inode) > - return NULL; > + if (inode) > + pr_warn_ratelimited( > +"block device autoloading is deprecated in will be removed in Linux 5.19\n"); s/deprecated in/deprecated; it/ > } > + if (!inode) > + return NULL; > > /* switch from the inode reference to a device mode one: */ > bdev = &BDEV_I(inode)->bdev;
diff --git a/block/Kconfig b/block/Kconfig index d5d4197b7ed2d..9cd8706faa7be 100644 --- a/block/Kconfig +++ b/block/Kconfig @@ -26,6 +26,17 @@ menuconfig BLOCK if BLOCK +config BLOCK_LEGACY_AUTOLOAD + bool "Legacy autoloading support" + help + Enable loading modules and creating block device instances based on + accesses through their device special file. This is a historic Linux + feature and makes no sense in a udev world where device files are + created on demand. + + Say N here unless your boot broke without it, in which case you should + send a report to linux-block@vger.kernel.org and your distribution. + config BLK_RQ_ALLOC_TIME bool diff --git a/block/bdev.c b/block/bdev.c index 8bf93a19041b7..dd6fd5b807b30 100644 --- a/block/bdev.c +++ b/block/bdev.c @@ -738,12 +738,15 @@ struct block_device *blkdev_get_no_open(dev_t dev) struct inode *inode; inode = ilookup(blockdev_superblock, dev); - if (!inode) { + if (!inode && IS_ENABLED(CONFIG_BLOCK_LEGACY_AUTOLOAD)) { blk_request_module(dev); inode = ilookup(blockdev_superblock, dev); - if (!inode) - return NULL; + if (inode) + pr_warn_ratelimited( +"block device autoloading is deprecated in will be removed in Linux 5.19\n"); } + if (!inode) + return NULL; /* switch from the inode reference to a device mode one: */ bdev = &BDEV_I(inode)->bdev; diff --git a/block/genhd.c b/block/genhd.c index 626c8406f21a6..6ae990ff02660 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -185,7 +185,9 @@ static struct blk_major_name { struct blk_major_name *next; int major; char name[16]; +#ifdef CONFIG_BLOCK_LEGACY_AUTOLOAD void (*probe)(dev_t devt); +#endif } *major_names[BLKDEV_MAJOR_HASH_SIZE]; static DEFINE_MUTEX(major_names_lock); static DEFINE_SPINLOCK(major_names_spinlock); @@ -275,7 +277,9 @@ int __register_blkdev(unsigned int major, const char *name, } p->major = major; +#ifdef CONFIG_BLOCK_LEGACY_AUTOLOAD p->probe = probe; +#endif strlcpy(p->name, name, sizeof(p->name)); p->next = NULL; index = major_to_index(major); @@ -679,6 +683,7 @@ static ssize_t disk_badblocks_store(struct device *dev, return badblocks_store(disk->bb, page, len, 0); } +#ifdef CONFIG_BLOCK_LEGACY_AUTOLOAD void blk_request_module(dev_t devt) { unsigned int major = MAJOR(devt); @@ -698,6 +703,7 @@ void blk_request_module(dev_t devt) /* Make old-style 2.4 aliases work */ request_module("block-major-%d", MAJOR(devt)); } +#endif /* CONFIG_BLOCK_LEGACY_AUTOLOAD */ /* * print a full list of all partitions - intended for places where the root
Make the legacy dev_t based autoloading optional and add a deprecation warning. This kind of autoloading has ceased to be useful about 20 years ago. Signed-off-by: Christoph Hellwig <hch@lst.de> --- block/Kconfig | 11 +++++++++++ block/bdev.c | 9 ++++++--- block/genhd.c | 6 ++++++ 3 files changed, 23 insertions(+), 3 deletions(-)