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Anton Altaparmakov authored
On 32-bit architectures, the legacy buffer_head functions are not always handling the sector number with the proper 64-bit types, and will thus fail on 4TB+ disks. Any code that uses __getblk() (and thus bread(), breadahead(), sb_bread(), sb_breadahead(), sb_getblk()), and calls it using a 64-bit block on a 32-bit arch (where "long" is 32-bit) causes an inifinite loop in __getblk_slow() with an infinite stream of errors logged to dmesg like this: __find_get_block_slow() failed. block=6740375944, b_blocknr=2445408648 b_state=0x00000020, b_size=512 device sda1 blocksize: 512 Note how in hex block is 0x191C1F988 and b_blocknr is 0x91C1F988 i.e. the top 32-bits are missing (in this case the 0x1 at the top). This is because grow_dev_page() is broken and has a 32-bit overflow due to shifting the page index value (a pgoff_t - which is just 32 bits on 32-bit architectures) left-shifted as the block number. But the top bits to get lost as the pgoff_t is not type cast to sector_t / 64-bit before the shift. This patch fixes this issue by type casting "index" to sector_t before doing the left shift. Note this is not a theoretical bug but has been seen in the field on a 4TiB hard drive with logical sector size 512 bytes. This patch has been verified to fix the infinite loop problem on 3.17-rc5 kernel using a 4TB disk image mounted using "-o loop". Without this patch doing a "find /nt" where /nt is an NTFS volume causes the inifinite loop 100% reproducibly whilst with the patch it works fine as expected. Signed-off-by:
Anton Altaparmakov <aia21@cantab.net> Cc: stable@vger.kernel.org Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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