XPost: linux.debian.bugs.dist   
   From: cassel@kernel.org   
      
   Hello Wolf,   
      
   On Wed, Jan 14, 2026 at 03:11:50PM +0000, Wolf wrote:   
   > Here is find-max-sectors.sh output:   
   >   
   > Drive model:   
   > INTEL SSDSC2KG480G8   
   >   
   > Drive firmware:   
   > XCV10120   
   >   
   > SATA / AHCI controller:   
   > 00:17.0 SATA controller [0106]: Intel Corporation Cannon Lake Mobile PCH   
   SATA AHCI Controller [8086:a353] (rev 10)   
   >   
   > Drive values before running the test:   
   > /sys/block/sda/queue/max_hw_sectors_kb:32767   
   > /sys/block/sda/queue/max_sectors_kb:1280   
   > /sys/block/sda/queue/read_ahead_kb:128   
   >   
   > Running test with max_sectors 128 KiB   
   > Test: PASS   
   >   
   > Running test with max_sectors 1024 KiB   
   > Test: PASS   
   >   
   > Running test with max_sectors 2048 KiB   
   > Test: PASS   
   >   
   > Running test with max_sectors 3072 KiB   
   > Test: PASS   
   >   
   > Running test with max_sectors 4095 KiB   
   > Test: PASS   
   >   
   > Running test with max_sectors 4096 KiB   
   > Test: PASS   
      
   It is quite unexpected that 4096 KiB passes.   
      
   find-max-sectors.sh performs reads.   
      
   The commands that timed out according to dmesg shared were   
   also reads:   
      
   Dec 10 18:58:49 kernel: ata1.00: failed command: READ FPDMA QUEUED   
   Dec 10 18:58:49 kernel: ata1.00: cmd 60/00:18:50:4a:4c/20:00:0c:00:00/40 tag 3   
   ncq dma 4194304 in res 40/00:00:00:00:00/00:00:00:00:00/00 Emask 0x4 (timeout)   
      
   And also of size 4194304 == 4096 KiB.   
      
      
   The script has been able to detect different limits for other   
   "broken" drives, and was used to get the quirk value for e.g.   
   commit 2e9832713631 ("ata: libata-core: Quirk DELLBOSS VD max_sectors"),   
   so I wonder why it is not workin here (why 4 MiB reads passes).   
      
   Damien, ideas?   
      
      
   Kind regards,   
   Niklas   
      
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