linux/drivers/block/floppy.c, branch v3.5

floppy: cancel any pending fd_timeouts before adding a new one

2012-07-03T22:51:22Z

In commit 070ad7e793dc ("floppy: convert to delayed work and single-thread wq") the 'fd_timeout' timer was converted to a delayed work. However, the "del_timer(&fd_timeout)" was lost in the process, and any previous pending timeouts would stay active when we then re-queued the timeout. This resulted in the floppy probe sequence having a (stale) 20s timeout rather than the intended 3s timeout, and thus made booting with the floppy driver (but no actual floppy controller) take much longer than it should. Of course, there's little reason for most people to compile the floppy driver into the kernel at all, which is why most people never noticed. Canceling the delayed work where we used to do the del_timer() fixes the issue, and makes the floppy probing use the proper new timeout instead. The three second timeout is still very wasteful, but better than the 20s one. Reported-and-tested-by: Andi Kleen Reported-and-tested-by: Calvin Walton Cc: Jiri Kosina Signed-off-by: Linus Torvalds

floppy: remove floppy-specific O_EXCL handling

2012-05-18T13:19:11Z

Block layer now handles O_EXCL in a generic way for block devices. The semantics is however different for floppy and all other block devices, as floppy driver contains its own O_EXCL handling. The semantics for all-but-floppy bdevs is "there can be at most one O_EXCL open of this file", while for floppy bdev the semantics is "if someone has the bdev open with O_EXCL, noone else can open it". There is actual userspace-observable change in behavior because of this since commit e525fd89d380c ("block: make blkdev_get/put() handle exclusive access") -- on kernels containing this commit, mount of /dev/fd0 causes the fd0 block device be claimed with _EXCL, preventing subsequent open(/dev/fd0). Bring things back into shape, i.e. make it possible, analogically to other block devices, to mount the floppy and open() it afterwards -- remove the floppy-specific handling and let the generic bdev code O_EXCL handling take over. Signed-off-by: Jiri Kosina Acked-by: Tejun Heo Acked-by: NeilBrown Signed-off-by: Andrew Morton Signed-off-by: Jiri Kosina

floppy: convert to delayed work and single-thread wq

2012-05-18T13:19:10Z

There are several races in floppy driver between bottom half (scheduled_work) and timers (fd_timeout, fd_timer). Due to slowness of the actual floppy devices, those races are never (at least to my knowledge) triggered on a bare floppy metal. However on virtualized (emulated) floppy drives, which are of course magnitudes faster than the real ones, these races trigger reliably. They usually exhibit themselves as NULL pointer dereferences during DMA setup, such as BUG: unable to handle kernel NULL pointer dereference at 0000000a [ ... snip ... ] EIP: 0060:[] EFLAGS: 00010293 CPU: 0 EAX: ffffe000 EBX: 0000000a ECX: 00000000 EDX: 0000000a ESI: c05d2718 EDI: 00000000 EBP: 00000000 ESP: f540fe44 DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 Process swapper (pid: 0, ti=f540e000 task=c082d5a0 task.ti=c0826000) Stack: ffffe000 00001ffc 00000000 00000000 00000000 c05d2718 c0708b40 f540fe80 c020470f c05d2718 c0708b40 00000000 f540fe80 0000000a f540fee4 00000000 c0708b40 f540fee4 00000000 00000000 c020526b 00000000 c05d2718 c0708b40 Call Trace: [] dump_trace+0xaf/0x110 [] show_trace_log_lvl+0x4b/0x60 [] show_trace+0x18/0x20 [] dump_stack+0x6d/0x72 [] warn_slowpath_common+0x77/0xb0 [] warn_slowpath_fmt+0x33/0x40 [] setup_DMA+0x14c/0x210 [floppy] [] setup_rw_floppy+0x105/0x190 [floppy] [] run_timer_softirq+0x168/0x2a0 [] __do_softirq+0xc2/0x1c0 [] do_softirq+0x7d/0xb0 [] 0xf54d89ff but other instances can be easily seen as well. This can be observed at least under VMWare, VirtualBox and KVM. This patch converts all the timers and bottom halfs to be processed in a single workqueue. This aproach has been already discussed back in 2010 if I remember correctly, and Acked by Linus [1], but it then never made it to the tree. This all is based on original idea and code of Stephen Hemminger. I have ported original Stepen's code to the current state of the floppy driver, and performed quite some testing (on real hardware), which didn't reveal any issues (this includes not only writing and reading data, but also formatting (unfortunately I didn't find any Double-Density disks any more)). Ability to handle errors properly (supplying known bad floppies) has also been verified. [1] http://kerneltrap.org/mailarchive/linux-kernel/2010/6/11/4582092 Based-on-patch-by: Stephen Hemminger Acked-by: Linus Torvalds Signed-off-by: Jiri Kosina

x86: Remove the ancient and deprecated disable_hlt() and enable_hlt() facility

2012-03-30T06:50:27Z

The X86_32-only disable_hlt/enable_hlt mechanism was used by the 32-bit floppy driver. Its effect was to replace the use of the HLT instruction inside default_idle() with cpu_relax() - essentially it turned off the use of HLT. This workaround was commented in the code as: "disable hlt during certain critical i/o operations" "This halt magic was a workaround for ancient floppy DMA wreckage. It should be safe to remove." H. Peter Anvin additionally adds: "To the best of my knowledge, no-hlt only existed because of flaky power distributions on 386/486 systems which were sold to run DOS. Since DOS did no power management of any kind, including HLT, the power draw was fairly uniform; when exposed to the much hhigher noise levels you got when Linux used HLT caused some of these systems to fail. They were by far in the minority even back then." Alan Cox further says: "Also for the Cyrix 5510 which tended to go castors up if a HLT occurred during a DMA cycle and on a few other boxes HLT during DMA tended to go astray. Do we care ? I doubt it. The 5510 was pretty obscure, the 5520 fixed it, the 5530 is probably the oldest still in any kind of use." So, let's finally drop this. Signed-off-by: Len Brown Signed-off-by: Josh Boyer Signed-off-by: Andrew Morton Acked-by: "H. Peter Anvin" Acked-by: Alan Cox Cc: Stephen Hemminger Cc: Link: http://lkml.kernel.org/n/tip-3rhk9bzf0x9rljkv488tloib@git.kernel.org [ If anyone cares then alternative instruction patching could be used to replace HLT with a one-byte NOP instruction. Much simpler. ] Signed-off-by: Ingo Molnar

Remove all #inclusions of asm/system.h

2012-03-28T17:30:03Z

Remove all #inclusions of asm/system.h preparatory to splitting and killing it. Performed with the following command: perl -p -i -e 's!^#\s*include\s*.*\n!!' `grep -Irl '^#\s*include\s*' *` Signed-off-by: David Howells

floppy/scsi: fix setting of BIO flags

2012-03-05T23:49:43Z

Fix setting bio flags in drivers (sd_dif/floppy). Signed-off-by: Muthukumar R Cc: Jens Axboe Cc: James Bottomley Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

floppy: Fix a crash during rmmod

2012-02-08T19:03:39Z

floppy driver does not call add_disk() on all the drives hence we don't take gendisk reference on request queue for these drives. Don't call put_disk() with disk->queue set, otherwise we try to put the reference we never took. Reported-and-tested-by: Dirk Gouders Signed-off-by: Vivek Goyal Acked-by: Tejun Heo Signed-off-by: Jens Axboe

floppy: Cleanup disk->queue before caling put_disk() if add_disk() was never called

2012-02-08T19:03:38Z

add_disk() takes gendisk reference on request queue. If driver failed during initialization and never called add_disk() then that extra reference is not taken. That reference is put in put_disk(). floppy driver allocates the disk, allocates queue, sets disk->queue and then relizes that floppy controller is not present. It tries to tear down everything and tries to put a reference down in put_disk() which was never taken. In such error cases cleanup disk->queue before calling put_disk() so that we never try to put down a reference which was never taken in first place. Reported-and-tested-by: Suresh Jayaraman Tested-by: Dirk Gouders Signed-off-by: Vivek Goyal Acked-by: Tejun Heo Signed-off-by: Jens Axboe

fs: move code out of buffer.c

2012-01-04T03:54:07Z

Move invalidate_bdev, block_sync_page into fs/block_dev.c. Export kill_bdev as well, so brd doesn't have to open code it. Reduce buffer_head.h requirement accordingly. Removed a rather large comment from invalidate_bdev, as it looked a bit obsolete to bother moving. The small comment replacing it says enough. Signed-off-by: Nick Piggin Cc: Al Viro Cc: Christoph Hellwig Signed-off-by: Andrew Morton Signed-off-by: Al Viro

floppy: use del_timer_sync() in init cleanup

2011-09-21T08:22:11Z

When no floppy is found the module code can be released while a timer function is pending or about to be executed. CPU0 CPU1 floppy_init() timer_softirq() spin_lock_irq(&base->lock); detach_timer(); spin_unlock_irq(&base->lock); -> Interrupt del_timer(); return -ENODEV; module_cleanup(); <- EOI call_timer_fn(); OOPS Use del_timer_sync() to prevent this. Signed-off-by: Carsten Emde Signed-off-by: Thomas Gleixner Cc: Jens Axboe Cc: Signed-off-by: Andrew Morton Signed-off-by: Jens Axboe