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author | Michael Ellerman <mpe@ellerman.id.au> | 2024-08-20 13:03:58 +1000 |
---|---|---|
committer | Damien Le Moal <dlemoal@kernel.org> | 2024-08-21 14:31:48 +0900 |
commit | 822c8020aebcf5804a143b891e34f29873fee5e2 (patch) | |
tree | f6baa59a0684d7662b5e216036d017f103508217 /drivers/ata | |
parent | fa0db8e568787c665384430eaf2221b299b85367 (diff) | |
download | lwn-822c8020aebcf5804a143b891e34f29873fee5e2.tar.gz lwn-822c8020aebcf5804a143b891e34f29873fee5e2.zip |
ata: pata_macio: Fix DMA table overflow
Kolbjørn and Jonáš reported that their 32-bit PowerMacs were crashing
in pata-macio since commit 09fe2bfa6b83 ("ata: pata_macio: Fix
max_segment_size with PAGE_SIZE == 64K").
For example:
kernel BUG at drivers/ata/pata_macio.c:544!
Oops: Exception in kernel mode, sig: 5 [#1]
BE PAGE_SIZE=4K MMU=Hash SMP NR_CPUS=2 DEBUG_PAGEALLOC PowerMac
...
NIP pata_macio_qc_prep+0xf4/0x190
LR pata_macio_qc_prep+0xfc/0x190
Call Trace:
0xc1421660 (unreliable)
ata_qc_issue+0x14c/0x2d4
__ata_scsi_queuecmd+0x200/0x53c
ata_scsi_queuecmd+0x50/0xe0
scsi_queue_rq+0x788/0xb1c
__blk_mq_issue_directly+0x58/0xf4
blk_mq_plug_issue_direct+0x8c/0x1b4
blk_mq_flush_plug_list.part.0+0x584/0x5e0
__blk_flush_plug+0xf8/0x194
__submit_bio+0x1b8/0x2e0
submit_bio_noacct_nocheck+0x230/0x304
btrfs_work_helper+0x200/0x338
process_one_work+0x1a8/0x338
worker_thread+0x364/0x4c0
kthread+0x100/0x104
start_kernel_thread+0x10/0x14
That commit increased max_segment_size to 64KB, with the justification
that the SCSI core was already using that size when PAGE_SIZE == 64KB,
and that there was existing logic to split over-sized requests.
However with a sufficiently large request, the splitting logic causes
each sg to be split into two commands in the DMA table, leading to
overflow of the DMA table, triggering the BUG_ON().
With default settings the bug doesn't trigger, because the request size
is limited by max_sectors_kb == 1280, however max_sectors_kb can be
increased, and apparently some distros do that by default using udev
rules.
Fix the bug for 4KB kernels by reverting to the old max_segment_size.
For 64KB kernels the sg_tablesize needs to be halved, to allow for the
possibility that each sg will be split into two.
Fixes: 09fe2bfa6b83 ("ata: pata_macio: Fix max_segment_size with PAGE_SIZE == 64K")
Cc: stable@vger.kernel.org # v6.10+
Reported-by: Kolbjørn Barmen <linux-ppc@kolla.no>
Closes: https://lore.kernel.org/all/62d248bb-e97a-25d2-bcf2-9160c518cae5@kolla.no/
Reported-by: Jonáš Vidra <vidra@ufal.mff.cuni.cz>
Closes: https://lore.kernel.org/all/3b6441b8-06e6-45da-9e55-f92f2c86933e@ufal.mff.cuni.cz/
Tested-by: Kolbjørn Barmen <linux-ppc@kolla.no>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Diffstat (limited to 'drivers/ata')
-rw-r--r-- | drivers/ata/pata_macio.c | 23 |
1 files changed, 15 insertions, 8 deletions
diff --git a/drivers/ata/pata_macio.c b/drivers/ata/pata_macio.c index 1b85e8bf4ef9..1cb8d24b088f 100644 --- a/drivers/ata/pata_macio.c +++ b/drivers/ata/pata_macio.c @@ -208,6 +208,19 @@ static const char* macio_ata_names[] = { /* Don't let a DMA segment go all the way to 64K */ #define MAX_DBDMA_SEG 0xff00 +#ifdef CONFIG_PAGE_SIZE_64KB +/* + * The SCSI core requires the segment size to cover at least a page, so + * for 64K page size kernels it must be at least 64K. However the + * hardware can't handle 64K, so pata_macio_qc_prep() will split large + * requests. To handle the split requests the tablesize must be halved. + */ +#define PATA_MACIO_MAX_SEGMENT_SIZE SZ_64K +#define PATA_MACIO_SG_TABLESIZE (MAX_DCMDS / 2) +#else +#define PATA_MACIO_MAX_SEGMENT_SIZE MAX_DBDMA_SEG +#define PATA_MACIO_SG_TABLESIZE MAX_DCMDS +#endif /* * Wait 1s for disk to answer on IDE bus after a hard reset @@ -912,16 +925,10 @@ static int pata_macio_do_resume(struct pata_macio_priv *priv) static const struct scsi_host_template pata_macio_sht = { __ATA_BASE_SHT(DRV_NAME), - .sg_tablesize = MAX_DCMDS, + .sg_tablesize = PATA_MACIO_SG_TABLESIZE, /* We may not need that strict one */ .dma_boundary = ATA_DMA_BOUNDARY, - /* - * The SCSI core requires the segment size to cover at least a page, so - * for 64K page size kernels this must be at least 64K. However the - * hardware can't handle 64K, so pata_macio_qc_prep() will split large - * requests. - */ - .max_segment_size = SZ_64K, + .max_segment_size = PATA_MACIO_MAX_SEGMENT_SIZE, .device_configure = pata_macio_device_configure, .sdev_groups = ata_common_sdev_groups, .can_queue = ATA_DEF_QUEUE, |