dma-debug: hash_bucket_find needs to allow for offsets within an entry

dma-debug: hash_bucket_find needs to allow for offsets within an entry

Summary:
Users of the pci_dma_sync_single_* api allow users to sync address ranges within
the range of a mapped entry (i.e. you can dma map address X to dma_addr_t A and
then pci_dma_sync_single on dma_addr_t A+1.  The dma-debug library however
assume dma syncs will always occur using the base address of a mapped region,
and uses that assumption to find entries in its hash table.  Since thats often
(but not always the case), the dma debug library can give us false errors about
missing entries, which are reported as syncing of memory not allocated by the
driver.  This was noted in the cxgb3 driver as this error:

WARNING: at lib/dma-debug.c:902 check_sync+0xdd/0x48c()
Hardware name: To be filled by O.E.M.
cxgb3 0000:01:00.0: DMA-API: device driver tries to sync DMA memory it has not
allocated [device address=0x00000000fff97800] [size=1984 bytes]
Modules linked in: autofs4 sunrpc cpufreq_ondemand acpi_cpufreq freq_table
mperf ip6t_REJECT nf_conntrack_ipv6 ip6table_filter ip6_tables ipv6 uinput
snd_hda_codec_intelhdmi snd_hda_codec_realtek snd_hda_intel snd_hda_codec
snd_hwdep snd_seq snd_seq_device snd_pcm snd_timer e1000e snd soundcore r8169
cxgb3 iTCO_wdt snd_page_alloc mii shpchp i2c_i801 iTCO_vendor_support mdio
microcode firewire_ohci firewire_core crc_itu_t ata_generic pata_acpi i915
drm_kms_helper drm i2c_algo_bit i2c_core video output [last unloaded:
scsi_wait_scan]
Pid: 1818, comm: ifconfig Not tainted 2.6.35-0.23.rc3.git6.fc14.x86_64 #1
Call Trace:
[<ffffffff81050f71>] warn_slowpath_common+0x85/0x9d
[<ffffffff8105102c>] warn_slowpath_fmt+0x46/0x48
[<ffffffff8124658e>] ? check_sync+0x39/0x48c
[<ffffffff8107c470>] ? trace_hardirqs_on+0xd/0xf
[<ffffffff81246632>] check_sync+0xdd/0x48c
[<ffffffff81246ca6>] debug_dma_sync_single_for_device+0x3f/0x41
[<ffffffffa011615c>] ? pci_map_page+0x84/0x97 [cxgb3]
[<ffffffffa0117bc3>] pci_dma_sync_single_for_device.clone.0+0x65/0x6e [cxgb3]
[<ffffffffa0117ed1>] refill_fl+0x305/0x30a [cxgb3]
[<ffffffffa011857d>] t3_sge_alloc_qset+0x6a7/0x821 [cxgb3]
[<ffffffffa010a07b>] cxgb_up+0x4d0/0xe62 [cxgb3]
[<ffffffff81086037>] ? __module_text_address+0x12/0x58
[<ffffffffa010aa4c>] cxgb_open+0x3f/0x309 [cxgb3]
[<ffffffff813e9f6c>] __dev_open+0x8e/0xbc
[<ffffffff813e7ca5>] __dev_change_flags+0xbe/0x142
[<ffffffff813e9ea8>] dev_change_flags+0x21/0x57
[<ffffffff81445937>] devinet_ioctl+0x29a/0x54b
[<ffffffff811f9a87>] ? inode_has_perm+0xaa/0xce
[<ffffffff81446ed2>] inet_ioctl+0x8f/0xa7
[<ffffffff813d683a>] sock_do_ioctl+0x29/0x48
[<ffffffff813d6c83>] sock_ioctl+0x213/0x222
[<ffffffff81137f78>] vfs_ioctl+0x32/0xa6
[<ffffffff811384e2>] do_vfs_ioctl+0x47a/0x4b3
[<ffffffff81138571>] sys_ioctl+0x56/0x79
[<ffffffff81009c32>] system_call_fastpath+0x16/0x1b
---[ end trace 69a4d4cc77b58004 ]---

(some edits by Joerg Roedel)

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Reported-by: Jay Fenalson <fenlason@redhat.com>
CC: Divy LeRay <divy@chelsio.com>
CC: Stanislaw Gruszka <sgruszka@redhat.com>
CC: Joerg Roedel <joerg.roedel@amd.com>
CC: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>