sbpcd oops on merged requests
PATCH 1/1 sbpcd oops on merged requests
Two fixes here - 1st is to make the new max_drives its own separate module parameter since the driver uses the existing sbpcd module parameter internally for more than just module parameters <sigh>.
2nd is more important - if you read more than 4 blocks from the device, you will get a random crash - meaning you could mount a cd and do "ls" and think it worked if that is all you did. Anything more gets a rolling oops, EIP pointing off into outer space etc.
Tracked this down to the addition of the generic merge request handling added to ll_rw_block in 2.3.41 (apparently nobody has used this driver since then!!!) - it appears these conflict with the molestation of the request list that sbpcd does from within.
Rather than attack sbpcd with a chainsaw, I went for the minimal patch approach and simply disabled request merging. Lets face it, performance is not an issue if you are using a 2x speed CD with seek times you measure with a wall calendar.
Patch is against 2.4.2-pre3.
Paul.
cdrom/sbpcd.c renamed from cdrom/sbpcd.c~ +32 -3
@@ -323,7 +323,7 @@* Andrew J. Kroll <[email protected]> Wed Jul 26 04:24:10 EDT 2000 * * 4.64 Fix module parameters - were being completely ignored. -* Can also specify max_drives as 3rd setup int to get rid of +* Can also specify max_drives=N as a setup int to get rid of * "ghost" drives on crap hardware (aren't they all?) Paul Gortmaker * * TODO
@@ -339,6 +339,15 @@* */ +/* +* Trying to merge requests breaks this driver horribly (as in it goes +* boom and apparently has done so since 2.3.41). As it is a legacy +* driver for a horribly slow double speed CD on a hideous interface +* designed for polled operation, I won't loose any sleep in simply +* disallowing merging. Paul G. 02/2001 +*/ +#define DONT_MERGE_REQUESTS +#ifndef SBPCD_ISSUE #define SBPCD_ISSUE 1#endif SBPCD_ISSUE
@@ -476,7 +485,8 @@#else static int sbpcd[] = {CDROM_PORT ,SBPRO };/* probe with user's setup only */ #endif -MODULE_PARM (sbpcd,"3i" ); +MODULE_PARM (sbpcd,"2i" ); +MODULE_PARM (max_drives,"i" );#define NUM_PROBE (sizeof(sbpcd) / sizeof(int))
@@ -5566,7 +5576,6 @@#else sbpcd_ioaddr = sbpcd[0 ]; sbpro_type = sbpcd[1 ]; - max_drives = sbpcd[2 ];#endif CDo_command=sbpcd_ioaddr;
@@ -5661,6 +5670,21 @@msg (DBG_SEQ ,"found SoundScape interface at %04X.\n" , sbpcd_ioaddr);return (0 ); } + +#ifdef DONT_MERGE_REQUESTS +static int dont_merge_requests_fn (request_queue_t *q,struct request *req, +struct request *next,int max_segments) +{ +return 0 ; +} + +static int dont_bh_merge_fn (request_queue_t *q,struct request *req, +struct buffer_head *bh,int max_segments) +{ +return 0 ; +} +#endif +/*==========================================================================*/ /* * Test for presence of drive and initialize it.
@@ -5828,6 +5852,11 @@#endif MODULE }blk_init_queue (BLK_DEFAULT_QUEUE (MAJOR_NR ),DEVICE_REQUEST ); +#ifdef DONT_MERGE_REQUESTS + (BLK_DEFAULT_QUEUE (MAJOR_NR ))->back_merge_fn = dont_bh_merge_fn; + (BLK_DEFAULT_QUEUE (MAJOR_NR ))->front_merge_fn = dont_bh_merge_fn; + (BLK_DEFAULT_QUEUE (MAJOR_NR ))->merge_requests_fn = dont_merge_requests_fn; +#endif blk_queue_headactive (BLK_DEFAULT_QUEUE (MAJOR_NR ),0 ); read_ahead[MAJOR_NR ] = buffers * (CD_FRAMESIZE /512 );
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