linux-v3.8-rc1 and later support for plug for blkdev_issue_discard with commit 0cfbcafcae8b7364b5fa96c2b26ccde7a3a296a9 (block: add plug for blkdev_issue_discard ) For example, 1) DISCARD rq-1 with size size 4GB 2) DISCARD rq-2 with size size 1GB If these 2 discard requests get merged, final request size will be 5GB. In this case, request's __data_len field may overflow as it can store max 4GB(unsigned int). This issue was observed while doing mkfs.f2fs on 5GB SD card: https://lkml.org/lkml/2013/4/1/292 Info: sector size = 512 Info: total sectors = 11370496 (in 512bytes) Info: zone aligned segment0 blkaddr: 512 [ 257.789764] blk_update_request: bio idx 0 >= vcnt 0 mkfs process gets stuck in D state and I see the following in the dmesg: [ 257.789733] __end_that: dev mmcblk0: type=1, flags=122c8081 [ 257.789764] sector 4194304, nr/cnr 2981888/4294959104 [ 257.789764] bio df3840c0, biotail df3848c0, buffer (null), len 1526726656 [ 257.789764] blk_update_request: bio idx 0 >= vcnt 0 [ 257.794921] request botched: dev mmcblk0: type=1, flags=122c8081 [ 257.794921] sector 4194304, nr/cnr 2981888/4294959104 [ 257.794921] bio df3840c0, biotail df3848c0, buffer (null), len 1526726656 This patch fixes this issue.
Unified · Split
| @@ -844,7 +844,7 @@ static inline unsigned int blk_queue_get_max_sectors(struct request_queue *q, · 843 unmodified lines | ||
| 844 | 844 | unsigned int cmd_flags) |
| 845 | 845 | { |
| 846 | 846 | if (unlikely(cmd_flags & REQ_DISCARD)) |
| 847 | − return q->limits.max_discard_sectors; | |
| 847 | + return min(q->limits.max_discard_sectors, UINT_MAX >> 9); | |
| 848 | 848 | |
| 849 | 849 | if (unlikely(cmd_flags & REQ_WRITE_SAME)) |
| 850 | 850 | return q->limits.max_write_same_sectors; |