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authorTaisuke Yamada <tai@rakugaki.org>2008-09-13 16:46:15 -0400
committerJeff Garzik <jgarzik@redhat.com>2008-09-13 16:46:15 -0400
commit97b697a11b07e2ebfa69c488132596cc5eb24119 (patch)
tree942176291faf6ab0dff6297708ca8b98f6e2e8c1 /.mailmap
parent99580664aa83ca04bb52988d504a4195b41833b0 (diff)
[libata] LBA28/LBA48 off-by-one bug in ata.h
I recently bought 3 HGST P7K500-series 500GB SATA drives and had trouble accessing the block right on the LBA28-LBA48 border. Here's how it fails (same for all 3 drives): # dd if=/dev/sdc bs=512 count=1 skip=268435455 > /dev/null dd: reading `/dev/sdc': Input/output error 0+0 records in 0+0 records out 0 bytes (0 B) copied, 0.288033 seconds, 0.0 kB/s # dmesg ata1.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x0 ata1.00: BMDMA stat 0x25 ata1.00: cmd c8/00:08:f8:ff:ff/00:00:00:00:00/ef tag 0 dma 4096 in res 51/04:08:f8:ff:ff/00:00:00:00:00/ef Emask 0x1 (device error) ata1.00: status: { DRDY ERR } ata1.00: error: { ABRT } ata1.00: configured for UDMA/33 ata1: EH complete ... After some investigations, it turned out this seems to be caused by misinterpretation of the ATA specification on LBA28 access. Following part is the code in question: === include/linux/ata.h === static inline int lba_28_ok(u64 block, u32 n_block) { /* check the ending block number */ return ((block + n_block - 1) < ((u64)1 << 28)) && (n_block <= 256); } HGST drive (sometimes) fails with LBA28 access of {block = 0xfffffff, n_block = 1}, and this behavior seems to be comformant. Other drives, including other HGST drives are not that strict, through. >From the ATA specification: (http://www.t13.org/Documents/UploadedDocuments/project/d1410r3b-ATA-ATAPI-6.pdf) 8.15.29 Word (61:60): Total number of user addressable sectors This field contains a value that is one greater than the total number of user addressable sectors (see 6.2). The maximum value that shall be placed in this field is 0FFFFFFFh. So the driver shouldn't use the value of 0xfffffff for LBA28 request as this exceeds maximum user addressable sector. The logical maximum value for LBA28 is 0xffffffe. The obvious fix is to cut "- 1" part, and the patch attached just do that. I've been using the patched kernel for about a month now, and the same fix is also floating on the net for some time. So I believe this fix works reliably. Just FYI, many Windows/Intel platform users also seems to be struck by this, and HGST has issued a note pointing to Intel ICH8/9 driver. "28-bit LBA command is being used to access LBAs 29-bits in length" http://www.hitachigst.com/hddt/knowtree.nsf/cffe836ed7c12018862565b000530c74/b531b8bce8745fb78825740f00580e23 Also, *BSDs seems to have similar fix included sometime around ~2004, through I have not checked out exact portion of the code. Signed-off-by: Taisuke Yamada <tai@rakugaki.org> Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
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