From e03c8dd14915fabc101aa495828d58598dc5af98 Mon Sep 17 00:00:00 2001 From: Kay Sievers Date: Tue, 23 Aug 2011 20:12:04 +0200 Subject: loop: always allow userspace partitions and optionally support automatic scanning Automatic partition scanning can be requested individually per loop device during its setup by setting LO_FLAGS_PARTSCAN. By default, no partition tables are scanned. Userspace can now always add and remove partitions from all loop devices, regardless if the in-kernel partition scanner is enabled or not. The needed partition minor numbers are allocated from the extended minors space, the main loop device numbers will continue to match the loop minors, regardless of the number of partitions used. # grep . /sys/class/block/loop1/loop/* /sys/block/loop1/loop/autoclear:0 /sys/block/loop1/loop/backing_file:/home/kay/data/stuff/part.img /sys/block/loop1/loop/offset:0 /sys/block/loop1/loop/partscan:1 /sys/block/loop1/loop/sizelimit:0 # ls -l /dev/loop* brw-rw---- 1 root disk 7, 0 Aug 14 20:22 /dev/loop0 brw-rw---- 1 root disk 7, 1 Aug 14 20:23 /dev/loop1 brw-rw---- 1 root disk 259, 0 Aug 14 20:23 /dev/loop1p1 brw-rw---- 1 root disk 259, 1 Aug 14 20:23 /dev/loop1p2 brw-rw---- 1 root disk 7, 99 Aug 14 20:23 /dev/loop99 brw-rw---- 1 root disk 259, 2 Aug 14 20:23 /dev/loop99p1 brw-rw---- 1 root disk 259, 3 Aug 14 20:23 /dev/loop99p2 crw------T 1 root root 10, 237 Aug 14 20:22 /dev/loop-control Cc: Karel Zak Cc: Davidlohr Bueso Acked-By: Tejun Heo Signed-off-by: Kay Sievers Signed-off-by: Jens Axboe --- include/linux/loop.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/loop.h') diff --git a/include/linux/loop.h b/include/linux/loop.h index 66c194e2d9b9..4367fc507fe9 100644 --- a/include/linux/loop.h +++ b/include/linux/loop.h @@ -76,6 +76,7 @@ enum { LO_FLAGS_READ_ONLY = 1, LO_FLAGS_USE_AOPS = 2, LO_FLAGS_AUTOCLEAR = 4, + LO_FLAGS_PARTSCAN = 8, }; #include /* for __kernel_old_dev_t */ -- cgit v1.2.3 From 456be1484ffc72a24bdb4200b5847c4fa90139d9 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Mon, 17 Oct 2011 12:57:20 +0200 Subject: loop: remove the incorrect write_begin/write_end shortcut Currently the loop device tries to call directly into write_begin/write_end instead of going through ->write if it can. This is a fairly nasty shortcut as write_begin and write_end are only callbacks for the generic write code and expect to be called with filesystem specific locks held. This code currently causes various issues for clustered filesystems as it doesn't take the required cluster locks, and it also causes issues for XFS as it doesn't properly lock against the swapext ioctl as called by the defragmentation tools. This in case causes data corruption if defragmentation hits a busy loop device in the wrong time window, as reported by RH QA. The reason why we have this shortcut is that it saves a data copy when doing a transformation on the loop device, which is the technical term for using cryptoloop (or an XOR transformation). Given that cryptoloop has been deprecated in favour of dm-crypt my opinion is that we should simply drop this shortcut instead of finding complicated ways to to introduce a formal interface for this shortcut. Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe --- include/linux/loop.h | 1 - 1 file changed, 1 deletion(-) (limited to 'include/linux/loop.h') diff --git a/include/linux/loop.h b/include/linux/loop.h index 683d69890119..a06880689115 100644 --- a/include/linux/loop.h +++ b/include/linux/loop.h @@ -73,7 +73,6 @@ struct loop_device { */ enum { LO_FLAGS_READ_ONLY = 1, - LO_FLAGS_USE_AOPS = 2, LO_FLAGS_AUTOCLEAR = 4, }; -- cgit v1.2.3