[PATCH 4/4] Reduce memory required for SCSI logging

[Bart Van Assche <bvanassche@xxxxxxx>]

The data structure used for log messages is so large that it can cause a
boot failure. Since allocations from that data structure can fail anyway,
use kmalloc() / kfree() instead of that data structure.

See also https://bugzilla.kernel.org/show_bug.cgi?id=204119.
See also commit ded85c193a39 ("scsi: Implement per-cpu logging buffer") # v4.0.

Reported-by: Jan Palus <jpalus@xxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxxx>
Cc: Johannes Thumshirn <jthumshirn@xxxxxxx>
Cc: Ming Lei <ming.lei@xxxxxxxxxx>
Cc: Jan Palus <jpalus@xxxxxxxxxxxx>
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
 drivers/scsi/scsi_logging.c | 48 +++----------------------------------
 include/scsi/scsi_dbg.h     |  2 --
 2 files changed, 3 insertions(+), 47 deletions(-)

diff --git a/drivers/scsi/scsi_logging.c b/drivers/scsi/scsi_logging.c
index 39b8cc4574b4..c6ed0b12e807 100644
--- a/drivers/scsi/scsi_logging.c
+++ b/drivers/scsi/scsi_logging.c
@@ -15,57 +15,15 @@
 #include <scsi/scsi_eh.h>
 #include <scsi/scsi_dbg.h>
 
-#define SCSI_LOG_SPOOLSIZE 4096
-
-#if (SCSI_LOG_SPOOLSIZE / SCSI_LOG_BUFSIZE) > BITS_PER_LONG
-#warning SCSI logging bitmask too large
-#endif
-
-struct scsi_log_buf {
-	char buffer[SCSI_LOG_SPOOLSIZE];
-	unsigned long map;
-};
-
-static DEFINE_PER_CPU(struct scsi_log_buf, scsi_format_log);
-
 static char *scsi_log_reserve_buffer(size_t *len)
 {
-	struct scsi_log_buf *buf;
-	unsigned long map_bits = sizeof(buf->buffer) / SCSI_LOG_BUFSIZE;
-	unsigned long idx = 0;
-
-	preempt_disable();
-	buf = this_cpu_ptr(&scsi_format_log);
-	idx = find_first_zero_bit(&buf->map, map_bits);
-	if (likely(idx < map_bits)) {
-		while (test_and_set_bit(idx, &buf->map)) {
-			idx = find_next_zero_bit(&buf->map, map_bits, idx);
-			if (idx >= map_bits)
-				break;
-		}
-	}
-	if (WARN_ON(idx >= map_bits)) {
-		preempt_enable();
-		return NULL;
-	}
-	*len = SCSI_LOG_BUFSIZE;
-	return buf->buffer + idx * SCSI_LOG_BUFSIZE;
+	*len = 128;
+	return kmalloc(*len, GFP_ATOMIC);
 }
 
 static void scsi_log_release_buffer(char *bufptr)
 {
-	struct scsi_log_buf *buf;
-	unsigned long idx;
-	int ret;
-
-	buf = this_cpu_ptr(&scsi_format_log);
-	if (bufptr >= buf->buffer &&
-	    bufptr < buf->buffer + SCSI_LOG_SPOOLSIZE) {
-		idx = (bufptr - buf->buffer) / SCSI_LOG_BUFSIZE;
-		ret = test_and_clear_bit(idx, &buf->map);
-		WARN_ON(!ret);
-	}
-	preempt_enable();
+	kfree(bufptr);
 }
 
 static inline const char *scmd_name(const struct scsi_cmnd *scmd)
diff --git a/include/scsi/scsi_dbg.h b/include/scsi/scsi_dbg.h
index e03bd9d41fa8..7b196d234626 100644
--- a/include/scsi/scsi_dbg.h
+++ b/include/scsi/scsi_dbg.h
@@ -6,8 +6,6 @@ struct scsi_cmnd;
 struct scsi_device;
 struct scsi_sense_hdr;
 
-#define SCSI_LOG_BUFSIZE 128
-
 extern void scsi_print_command(struct scsi_cmnd *);
 extern size_t __scsi_format_command(char *, size_t,
 				   const unsigned char *, size_t);
-- 
2.22.0.709.g102302147b-goog