6.10-stable review patch. If anyone has any objections, please let me know.
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From: Michael Ellerman mpe@ellerman.id.au
commit 822c8020aebcf5804a143b891e34f29873fee5e2 upstream.
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.cu... 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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/ata/pata_macio.c | 23 +++++++++++++++-------- 1 file 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,