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b87570f5d3
The kernel may crash when block size is changed and I/O is issued simultaneously. Because some subsystems (udev or lvm) may read any block device anytime, the bug actually puts any code that changes a block device size in jeopardy. The crash can be reproduced if you place "msleep(1000)" to blkdev_get_blocks just before "bh->b_size = max_blocks << inode->i_blkbits;". Then, run "dd if=/dev/ram0 of=/dev/null bs=4k count=1 iflag=direct" While it is waiting in msleep, run "blockdev --setbsz 2048 /dev/ram0" You get a BUG. The direct and non-direct I/O is written with the assumption that block size does not change. It doesn't seem practical to fix these crashes one-by-one there may be many crash possibilities when block size changes at a certain place and it is impossible to find them all and verify the code. This patch introduces a new rw-lock bd_block_size_semaphore. The lock is taken for read during I/O. It is taken for write when changing block size. Consequently, block size can't be changed while I/O is being submitted. For asynchronous I/O, the patch only prevents block size change while the I/O is being submitted. The block size can change when the I/O is in progress or when the I/O is being finished. This is acceptable because there are no accesses to block size when asynchronous I/O is being finished. The patch prevents block size changing while the device is mapped with mmap. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk> |
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| .. | ||
| agp | ||
| hw_random | ||
| ipmi | ||
| mwave | ||
| pcmcia | ||
| tpm | ||
| xilinx_hwicap | ||
| apm-emulation.c | ||
| applicom.c | ||
| applicom.h | ||
| bfin-otp.c | ||
| bsr.c | ||
| ds1302.c | ||
| ds1620.c | ||
| dsp56k.c | ||
| dtlk.c | ||
| efirtc.c | ||
| generic_nvram.c | ||
| genrtc.c | ||
| hangcheck-timer.c | ||
| hpet.c | ||
| i8k.c | ||
| Kconfig | ||
| lp.c | ||
| Makefile | ||
| mbcs.c | ||
| mbcs.h | ||
| mem.c | ||
| misc.c | ||
| mmtimer.c | ||
| msm_smd_pkt.c | ||
| mspec.c | ||
| nsc_gpio.c | ||
| nvram.c | ||
| nwbutton.c | ||
| nwbutton.h | ||
| nwflash.c | ||
| pc8736x_gpio.c | ||
| ppdev.c | ||
| ps3flash.c | ||
| random.c | ||
| raw.c | ||
| rtc.c | ||
| scx200_gpio.c | ||
| snsc.c | ||
| snsc.h | ||
| snsc_event.c | ||
| sonypi.c | ||
| tb0219.c | ||
| tile-srom.c | ||
| tlclk.c | ||
| toshiba.c | ||
| ttyprintk.c | ||
| uv_mmtimer.c | ||
| virtio_console.c | ||