Merge branch 'linux-next' of git://git.infradead.org/ubi-2.6

* 'linux-next' of git://git.infradead.org/ubi-2.6:
  UBI: make tests modes dynamic
  UBI: make self-checks dynamic
  UBI: make debugging messages dynamic
  UBI: remove UBI_IO_DEBUG macro
  UBI: kill debugging buffer
  UBI: allocate erase checking buffer on demand
  UBI: allocate write checking buffer on demand
  UBI: always re-read in case of read failures
  UBI: cleanup comments about corrupted PEBs
  UBI: add slab cache for ubi_scan_leb objects
  UBI: use raw mtd read function in debugging code
  UBI: try to reveal buggy MTD drivers
  UBI: add a commentary about allocating VID header buffer on stack
  UBI: cleanup LEB start calculations
  UBI: fix NOR erase preparation quirk

drivers/mtd/ubi/Kconfig

@@ -52,6 +52,12 @@ config MTD_UBI_GLUEBI
 	   work on top of UBI. Do not enable this unless you use legacy
 	   software.
 
-source "drivers/mtd/ubi/Kconfig.debug"
+config MTD_UBI_DEBUG
+	bool "UBI debugging"
+	depends on SYSFS
+	select DEBUG_FS
+	select KALLSYMS_ALL if KALLSYMS && DEBUG_KERNEL
+	help
+	  This option enables UBI debugging.
 
 endif # MTD_UBI

drivers/mtd/ubi/Kconfig.debug

-comment "UBI debugging options"
-
-config MTD_UBI_DEBUG
-	bool "UBI debugging"
-	depends on SYSFS
-	select DEBUG_FS
-	select KALLSYMS_ALL if KALLSYMS && DEBUG_KERNEL
-	help
-	  This option enables UBI debugging.
-
-if MTD_UBI_DEBUG
-
-config MTD_UBI_DEBUG_MSG
-	bool "UBI debugging messages"
-	help
-	  This option enables UBI debugging messages.
-
-config MTD_UBI_DEBUG_PARANOID
-	bool "Extra self-checks"
-	help
-	  This option enables extra checks in UBI code. Note this slows UBI down
-	  significantly.
-
-config MTD_UBI_DEBUG_DISABLE_BGT
-	bool "Do not enable the UBI background thread"
-	help
-	  This option switches the background thread off by default. The thread
-	  may be also be enabled/disabled via UBI sysfs.
-
-config MTD_UBI_DEBUG_EMULATE_BITFLIPS
-	bool "Emulate flash bit-flips"
-	help
-	  This option emulates bit-flips with probability 1/50, which in turn
-	  causes scrubbing. Useful for debugging and stressing UBI.
-
-config MTD_UBI_DEBUG_EMULATE_WRITE_FAILURES
-	bool "Emulate flash write failures"
-	help
-	  This option emulates write failures with probability 1/100. Useful for
-	  debugging and testing how UBI handlines errors.
-
-config MTD_UBI_DEBUG_EMULATE_ERASE_FAILURES
-	bool "Emulate flash erase failures"
-	help
-	  This option emulates erase failures with probability 1/100. Useful for
-	  debugging and testing how UBI handlines errors.
-
-comment "Additional UBI debugging messages"
-
-config MTD_UBI_DEBUG_MSG_BLD
-	bool "Additional UBI initialization and build messages"
-	help
-	  This option enables detailed UBI initialization and device build
-	  debugging messages.
-
-config MTD_UBI_DEBUG_MSG_EBA
-	bool "Eraseblock association unit messages"
-	help
-	  This option enables debugging messages from the UBI eraseblock
-	  association unit.
-
-config MTD_UBI_DEBUG_MSG_WL
-	bool "Wear-leveling unit messages"
-	help
-	  This option enables debugging messages from the UBI wear-leveling
-	  unit.
-
-config MTD_UBI_DEBUG_MSG_IO
-	bool "Input/output unit messages"
-	help
-	  This option enables debugging messages from the UBI input/output unit.
-
-endif # MTD_UBI_DEBUG

drivers/mtd/ubi/build.c

@@ -711,7 +711,7 @@ static int io_init(struct ubi_device *ubi)
 	}
 
 	/* Similar for the data offset */
-	ubi->leb_start = ubi->vid_hdr_offset + UBI_EC_HDR_SIZE;
+	ubi->leb_start = ubi->vid_hdr_offset + UBI_VID_HDR_SIZE;
 	ubi->leb_start = ALIGN(ubi->leb_start, ubi->min_io_size);
 
 	dbg_msg("vid_hdr_offset   %d", ubi->vid_hdr_offset);
@@ -923,6 +923,8 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num, int vid_hdr_offset)
 	spin_lock_init(&ubi->volumes_lock);
 
 	ubi_msg("attaching mtd%d to ubi%d", mtd->index, ubi_num);
+	dbg_msg("sizeof(struct ubi_scan_leb) %zu", sizeof(struct ubi_scan_leb));
+	dbg_msg("sizeof(struct ubi_wl_entry) %zu", sizeof(struct ubi_wl_entry));
 
 	err = io_init(ubi);
 	if (err)
@@ -937,13 +939,6 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num, int vid_hdr_offset)
 	if (!ubi->peb_buf2)
 		goto out_free;
 
-#ifdef CONFIG_MTD_UBI_DEBUG_PARANOID
-	mutex_init(&ubi->dbg_buf_mutex);
-	ubi->dbg_peb_buf = vmalloc(ubi->peb_size);
-	if (!ubi->dbg_peb_buf)
-		goto out_free;
-#endif
-
 	err = attach_by_scanning(ubi);
 	if (err) {
 		dbg_err("failed to attach by scanning, error %d", err);
@@ -991,8 +986,7 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num, int vid_hdr_offset)
 	 * checks @ubi->thread_enabled. Otherwise we may fail to wake it up.
 	 */
 	spin_lock(&ubi->wl_lock);
-	if (!DBG_DISABLE_BGT)
-		ubi->thread_enabled = 1;
+	ubi->thread_enabled = 1;
 	wake_up_process(ubi->bgt_thread);
 	spin_unlock(&ubi->wl_lock);
 
@@ -1009,9 +1003,6 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num, int vid_hdr_offset)
 out_free:
 	vfree(ubi->peb_buf1);
 	vfree(ubi->peb_buf2);
-#ifdef CONFIG_MTD_UBI_DEBUG_PARANOID
-	vfree(ubi->dbg_peb_buf);
-#endif
 	if (ref)
 		put_device(&ubi->dev);
 	else
@@ -1082,9 +1073,6 @@ int ubi_detach_mtd_dev(int ubi_num, int anyway)
 	put_mtd_device(ubi->mtd);
 	vfree(ubi->peb_buf1);
 	vfree(ubi->peb_buf2);
-#ifdef CONFIG_MTD_UBI_DEBUG_PARANOID
-	vfree(ubi->dbg_peb_buf);
-#endif
 	ubi_msg("mtd%d is detached from ubi%d", ubi->mtd->index, ubi->ubi_num);
 	put_device(&ubi->dev);
 	return 0;

drivers/mtd/ubi/debug.c

@@ -27,6 +27,20 @@
 #ifdef CONFIG_MTD_UBI_DEBUG
 
 #include "ubi.h"
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+
+unsigned int ubi_msg_flags;
+unsigned int ubi_chk_flags;
+unsigned int ubi_tst_flags;
+
+module_param_named(debug_msgs, ubi_msg_flags, uint, S_IRUGO | S_IWUSR);
+module_param_named(debug_chks, ubi_chk_flags, uint, S_IRUGO | S_IWUSR);
+module_param_named(debug_tsts, ubi_chk_flags, uint, S_IRUGO | S_IWUSR);
+
+MODULE_PARM_DESC(debug_msgs, "Debug message type flags");
+MODULE_PARM_DESC(debug_chks, "Debug check flags");
+MODULE_PARM_DESC(debug_tsts, "Debug special test flags");
 
 /**
  * ubi_dbg_dump_ec_hdr - dump an erase counter header.

drivers/mtd/ubi/debug.h

@@ -38,6 +38,11 @@
 	printk(KERN_DEBUG "UBI DBG (pid %d): %s: " fmt "\n", \
 	       current->pid, __func__, ##__VA_ARGS__)
 
+#define dbg_do_msg(typ, fmt, ...) do {                       \
+	if (ubi_msg_flags & typ)                             \
+		dbg_msg(fmt, ##__VA_ARGS__);                 \
+} while (0)
+
 #define ubi_dbg_dump_stack() dump_stack()
 
 struct ubi_ec_hdr;
@@ -57,62 +62,88 @@ void ubi_dbg_dump_seb(const struct ubi_scan_leb *seb, int type);
 void ubi_dbg_dump_mkvol_req(const struct ubi_mkvol_req *req);
 void ubi_dbg_dump_flash(struct ubi_device *ubi, int pnum, int offset, int len);
 
+extern unsigned int ubi_msg_flags;
+
+/*
+ * Debugging message type flags (must match msg_type_names in debug.c).
+ *
+ * UBI_MSG_GEN: general messages
+ * UBI_MSG_EBA: journal messages
+ * UBI_MSG_WL: mount messages
+ * UBI_MSG_IO: commit messages
+ * UBI_MSG_BLD: LEB find messages
+ */
+enum {
+	UBI_MSG_GEN  = 0x1,
+	UBI_MSG_EBA  = 0x2,
+	UBI_MSG_WL   = 0x4,
+	UBI_MSG_IO   = 0x8,
+	UBI_MSG_BLD  = 0x10,
+};
+
 #define ubi_dbg_print_hex_dump(l, ps, pt, r, g, b, len, a)  \
 		print_hex_dump(l, ps, pt, r, g, b, len, a)
 
-#ifdef CONFIG_MTD_UBI_DEBUG_MSG
 /* General debugging messages */
-#define dbg_gen(fmt, ...) dbg_msg(fmt, ##__VA_ARGS__)
-#else
-#define dbg_gen(fmt, ...) ({})
-#endif
+#define dbg_gen(fmt, ...) dbg_do_msg(UBI_MSG_GEN, fmt, ##__VA_ARGS__)
 
-#ifdef CONFIG_MTD_UBI_DEBUG_MSG_EBA
 /* Messages from the eraseblock association sub-system */
-#define dbg_eba(fmt, ...) dbg_msg(fmt, ##__VA_ARGS__)
-#else
-#define dbg_eba(fmt, ...) ({})
-#endif
+#define dbg_eba(fmt, ...) dbg_do_msg(UBI_MSG_EBA, fmt, ##__VA_ARGS__)
 
-#ifdef CONFIG_MTD_UBI_DEBUG_MSG_WL
 /* Messages from the wear-leveling sub-system */
-#define dbg_wl(fmt, ...) dbg_msg(fmt, ##__VA_ARGS__)
-#else
-#define dbg_wl(fmt, ...) ({})
-#endif
+#define dbg_wl(fmt, ...) dbg_do_msg(UBI_MSG_WL, fmt, ##__VA_ARGS__)
 
-#ifdef CONFIG_MTD_UBI_DEBUG_MSG_IO
 /* Messages from the input/output sub-system */
-#define dbg_io(fmt, ...) dbg_msg(fmt, ##__VA_ARGS__)
-#else
-#define dbg_io(fmt, ...) ({})
-#endif
+#define dbg_io(fmt, ...) dbg_do_msg(UBI_MSG_IO, fmt, ##__VA_ARGS__)
 
-#ifdef CONFIG_MTD_UBI_DEBUG_MSG_BLD
 /* Initialization and build messages */
-#define dbg_bld(fmt, ...) dbg_msg(fmt, ##__VA_ARGS__)
-#define UBI_IO_DEBUG 1
-#else
-#define dbg_bld(fmt, ...) ({})
-#define UBI_IO_DEBUG 0
-#endif
+#define dbg_bld(fmt, ...) dbg_do_msg(UBI_MSG_BLD, fmt, ##__VA_ARGS__)
+
+extern unsigned int ubi_chk_flags;
+
+/*
+ * Debugging check flags.
+ *
+ * UBI_CHK_GEN: general checks
+ * UBI_CHK_IO: check writes and erases
+ */
+enum {
+	UBI_CHK_GEN = 0x1,
+	UBI_CHK_IO  = 0x2,
+};
 
-#ifdef CONFIG_MTD_UBI_DEBUG_PARANOID
 int ubi_dbg_check_all_ff(struct ubi_device *ubi, int pnum, int offset, int len);
 int ubi_dbg_check_write(struct ubi_device *ubi, const void *buf, int pnum,
 			int offset, int len);
-#else
-#define ubi_dbg_check_all_ff(ubi, pnum, offset, len) 0
-#define ubi_dbg_check_write(ubi, buf, pnum, offset, len) 0
-#endif
 
-#ifdef CONFIG_MTD_UBI_DEBUG_DISABLE_BGT
-#define DBG_DISABLE_BGT 1
-#else
-#define DBG_DISABLE_BGT 0
-#endif
+extern unsigned int ubi_tst_flags;
+
+/*
+ * Special testing flags.
+ *
+ * UBIFS_TST_DISABLE_BGT: disable the background thread
+ * UBI_TST_EMULATE_BITFLIPS: emulate bit-flips
+ * UBI_TST_EMULATE_WRITE_FAILURES: emulate write failures
+ * UBI_TST_EMULATE_ERASE_FAILURES: emulate erase failures
+ */
+enum {
+	UBI_TST_DISABLE_BGT            = 0x1,
+	UBI_TST_EMULATE_BITFLIPS       = 0x2,
+	UBI_TST_EMULATE_WRITE_FAILURES = 0x4,
+	UBI_TST_EMULATE_ERASE_FAILURES = 0x8,
+};
+
+/**
+ * ubi_dbg_is_bgt_disabled - if the background thread is disabled.
+ *
+ * Returns non-zero if the UBI background thread is disabled for testing
+ * purposes.
+ */
+static inline int ubi_dbg_is_bgt_disabled(void)
+{
+	return ubi_tst_flags & UBI_TST_DISABLE_BGT;
+}
 
-#ifdef CONFIG_MTD_UBI_DEBUG_EMULATE_BITFLIPS
 /**
  * ubi_dbg_is_bitflip - if it is time to emulate a bit-flip.
  *
@@ -120,13 +151,11 @@ int ubi_dbg_check_write(struct ubi_device *ubi, const void *buf, int pnum,
  */
 static inline int ubi_dbg_is_bitflip(void)
 {
-	return !(random32() % 200);
+	if (ubi_tst_flags & UBI_TST_EMULATE_BITFLIPS)
+		return !(random32() % 200);
+	return 0;
 }
-#else
-#define ubi_dbg_is_bitflip() 0
-#endif
 
-#ifdef CONFIG_MTD_UBI_DEBUG_EMULATE_WRITE_FAILURES
 /**
  * ubi_dbg_is_write_failure - if it is time to emulate a write failure.
  *
@@ -135,13 +164,11 @@ static inline int ubi_dbg_is_bitflip(void)
  */
 static inline int ubi_dbg_is_write_failure(void)
 {
-	return !(random32() % 500);
+	if (ubi_tst_flags & UBI_TST_EMULATE_WRITE_FAILURES)
+		return !(random32() % 500);
+	return 0;
 }
-#else
-#define ubi_dbg_is_write_failure() 0
-#endif
 
-#ifdef CONFIG_MTD_UBI_DEBUG_EMULATE_ERASE_FAILURES
 /**
  * ubi_dbg_is_erase_failure - if its time to emulate an erase failure.
  *
@@ -150,11 +177,10 @@ static inline int ubi_dbg_is_write_failure(void)
  */
 static inline int ubi_dbg_is_erase_failure(void)
 {
+	if (ubi_tst_flags & UBI_TST_EMULATE_ERASE_FAILURES)
 		return !(random32() % 400);
+	return 0;
 }
-#else
-#define ubi_dbg_is_erase_failure() 0
-#endif
 
 #else
 
@@ -177,8 +203,7 @@ static inline int ubi_dbg_is_erase_failure(void)
 #define ubi_dbg_dump_flash(ubi, pnum, offset, len) ({})
 #define ubi_dbg_print_hex_dump(l, ps, pt, r, g, b, len, a)  ({})
 
-#define UBI_IO_DEBUG               0
-#define DBG_DISABLE_BGT            0
+#define ubi_dbg_is_bgt_disabled()  0
 #define ubi_dbg_is_bitflip()       0
 #define ubi_dbg_is_write_failure() 0
 #define ubi_dbg_is_erase_failure() 0

drivers/mtd/ubi/io.c

@@ -91,7 +91,7 @@
 #include <linux/slab.h>
 #include "ubi.h"
 
-#ifdef CONFIG_MTD_UBI_DEBUG_PARANOID
+#ifdef CONFIG_MTD_UBI_DEBUG
 static int paranoid_check_not_bad(const struct ubi_device *ubi, int pnum);
 static int paranoid_check_peb_ec_hdr(const struct ubi_device *ubi, int pnum);
 static int paranoid_check_ec_hdr(const struct ubi_device *ubi, int pnum,
@@ -146,6 +146,28 @@ int ubi_io_read(const struct ubi_device *ubi, void *buf, int pnum, int offset,
 	if (err)
 		return err;
 
+	/*
+	 * Deliberately corrupt the buffer to improve robustness. Indeed, if we
+	 * do not do this, the following may happen:
+	 * 1. The buffer contains data from previous operation, e.g., read from
+	 *    another PEB previously. The data looks like expected, e.g., if we
+	 *    just do not read anything and return - the caller would not
+	 *    notice this. E.g., if we are reading a VID header, the buffer may
+	 *    contain a valid VID header from another PEB.
+	 * 2. The driver is buggy and returns us success or -EBADMSG or
+	 *    -EUCLEAN, but it does not actually put any data to the buffer.
+	 *
+	 * This may confuse UBI or upper layers - they may think the buffer
+	 * contains valid data while in fact it is just old data. This is
+	 * especially possible because UBI (and UBIFS) relies on CRC, and
+	 * treats data as correct even in case of ECC errors if the CRC is
+	 * correct.
+	 *
+	 * Try to prevent this situation by changing the first byte of the
+	 * buffer.
+	 */
+	*((uint8_t *)buf) ^= 0xFF;
+
 	addr = (loff_t)pnum * ubi->peb_size + offset;
 retry:
 	err = ubi->mtd->read(ubi->mtd, addr, len, &read, buf);
@@ -166,7 +188,7 @@ int ubi_io_read(const struct ubi_device *ubi, void *buf, int pnum, int offset,
 			return UBI_IO_BITFLIPS;
 		}
 
-		if (read != len && retries++ < UBI_IO_RETRIES) {
+		if (retries++ < UBI_IO_RETRIES) {
 			dbg_io("error %d%s while reading %d bytes from PEB %d:%d,"
 			       " read only %zd bytes, retry",
 			       err, errstr, len, pnum, offset, read);
@@ -480,6 +502,13 @@ static int nor_erase_prepare(struct ubi_device *ubi, int pnum)
 	size_t written;
 	loff_t addr;
 	uint32_t data = 0;
+	/*
+	 * Note, we cannot generally define VID header buffers on stack,
+	 * because of the way we deal with these buffers (see the header
+	 * comment in this file). But we know this is a NOR-specific piece of
+	 * code, so we can do this. But yes, this is error-prone and we should
+	 * (pre-)allocate VID header buffer instead.
+	 */
 	struct ubi_vid_hdr vid_hdr;
 
 	/*
@@ -507,11 +536,13 @@ static int nor_erase_prepare(struct ubi_device *ubi, int pnum)
 	 * PEB.
 	 */
 	err1 = ubi_io_read_vid_hdr(ubi, pnum, &vid_hdr, 0);
-	if (err1 == UBI_IO_BAD_HDR_EBADMSG || err1 == UBI_IO_BAD_HDR) {
+	if (err1 == UBI_IO_BAD_HDR_EBADMSG || err1 == UBI_IO_BAD_HDR ||
+	    err1 == UBI_IO_FF) {
 		struct ubi_ec_hdr ec_hdr;
 
 		err1 = ubi_io_read_ec_hdr(ubi, pnum, &ec_hdr, 0);
-		if (err1 == UBI_IO_BAD_HDR_EBADMSG || err1 == UBI_IO_BAD_HDR)
+		if (err1 == UBI_IO_BAD_HDR_EBADMSG || err1 == UBI_IO_BAD_HDR ||
+		    err1 == UBI_IO_FF)
 			/*
 			 * Both VID and EC headers are corrupted, so we can
 			 * safely erase this PEB and not afraid that it will be
@@ -752,9 +783,8 @@ int ubi_io_read_ec_hdr(struct ubi_device *ubi, int pnum,
 			if (verbose)
 				ubi_warn("no EC header found at PEB %d, "
 					 "only 0xFF bytes", pnum);
-			else if (UBI_IO_DEBUG)
-				dbg_msg("no EC header found at PEB %d, "
-					"only 0xFF bytes", pnum);
+			dbg_bld("no EC header found at PEB %d, "
+				"only 0xFF bytes", pnum);
 			if (!read_err)
 				return UBI_IO_FF;
 			else
@@ -769,9 +799,9 @@ int ubi_io_read_ec_hdr(struct ubi_device *ubi, int pnum,
 			ubi_warn("bad magic number at PEB %d: %08x instead of "
 				 "%08x", pnum, magic, UBI_EC_HDR_MAGIC);
 			ubi_dbg_dump_ec_hdr(ec_hdr);
-		} else if (UBI_IO_DEBUG)
-			dbg_msg("bad magic number at PEB %d: %08x instead of "
-				"%08x", pnum, magic, UBI_EC_HDR_MAGIC);
+		}
+		dbg_bld("bad magic number at PEB %d: %08x instead of "
+			"%08x", pnum, magic, UBI_EC_HDR_MAGIC);
 		return UBI_IO_BAD_HDR;
 	}
 
@@ -783,9 +813,9 @@ int ubi_io_read_ec_hdr(struct ubi_device *ubi, int pnum,
 			ubi_warn("bad EC header CRC at PEB %d, calculated "
 				 "%#08x, read %#08x", pnum, crc, hdr_crc);
 			ubi_dbg_dump_ec_hdr(ec_hdr);
-		} else if (UBI_IO_DEBUG)
-			dbg_msg("bad EC header CRC at PEB %d, calculated "
-				"%#08x, read %#08x", pnum, crc, hdr_crc);
+		}
+		dbg_bld("bad EC header CRC at PEB %d, calculated "
+			"%#08x, read %#08x", pnum, crc, hdr_crc);
 
 		if (!read_err)
 			return UBI_IO_BAD_HDR;
@@ -1008,9 +1038,8 @@ int ubi_io_read_vid_hdr(struct ubi_device *ubi, int pnum,
 			if (verbose)
 				ubi_warn("no VID header found at PEB %d, "
 					 "only 0xFF bytes", pnum);
-			else if (UBI_IO_DEBUG)
-				dbg_msg("no VID header found at PEB %d, "
-					"only 0xFF bytes", pnum);
+			dbg_bld("no VID header found at PEB %d, "
+				"only 0xFF bytes", pnum);
 			if (!read_err)
 				return UBI_IO_FF;
 			else
@@ -1021,9 +1050,9 @@ int ubi_io_read_vid_hdr(struct ubi_device *ubi, int pnum,
 			ubi_warn("bad magic number at PEB %d: %08x instead of "
 				 "%08x", pnum, magic, UBI_VID_HDR_MAGIC);
 			ubi_dbg_dump_vid_hdr(vid_hdr);
-		} else if (UBI_IO_DEBUG)
-			dbg_msg("bad magic number at PEB %d: %08x instead of "
-				"%08x", pnum, magic, UBI_VID_HDR_MAGIC);
+		}
+		dbg_bld("bad magic number at PEB %d: %08x instead of "
+			"%08x", pnum, magic, UBI_VID_HDR_MAGIC);
 		return UBI_IO_BAD_HDR;
 	}
 
@@ -1035,9 +1064,9 @@ int ubi_io_read_vid_hdr(struct ubi_device *ubi, int pnum,
 			ubi_warn("bad CRC at PEB %d, calculated %#08x, "
 				 "read %#08x", pnum, crc, hdr_crc);
 			ubi_dbg_dump_vid_hdr(vid_hdr);
-		} else if (UBI_IO_DEBUG)
-			dbg_msg("bad CRC at PEB %d, calculated %#08x, "
-				"read %#08x", pnum, crc, hdr_crc);
+		}
+		dbg_bld("bad CRC at PEB %d, calculated %#08x, "
+			"read %#08x", pnum, crc, hdr_crc);
 		if (!read_err)
 			return UBI_IO_BAD_HDR;
 		else
@@ -1097,7 +1126,7 @@ int ubi_io_write_vid_hdr(struct ubi_device *ubi, int pnum,
 	return err;
 }
 
-#ifdef CONFIG_MTD_UBI_DEBUG_PARANOID
+#ifdef CONFIG_MTD_UBI_DEBUG
 
 /**
  * paranoid_check_not_bad - ensure that a physical eraseblock is not bad.
@@ -1111,6 +1140,9 @@ static int paranoid_check_not_bad(const struct ubi_device *ubi, int pnum)
 {
 	int err;
 
+	if (!(ubi_chk_flags & UBI_CHK_IO))
+		return 0;
+
 	err = ubi_io_is_bad(ubi, pnum);
 	if (!err)
 		return err;
@@ -1135,6 +1167,9 @@ static int paranoid_check_ec_hdr(const struct ubi_device *ubi, int pnum,
 	int err;
 	uint32_t magic;
 
+	if (!(ubi_chk_flags & UBI_CHK_IO))
+		return 0;
+
 	magic = be32_to_cpu(ec_hdr->magic);
 	if (magic != UBI_EC_HDR_MAGIC) {
 		ubi_err("bad magic %#08x, must be %#08x",
@@ -1170,6 +1205,9 @@ static int paranoid_check_peb_ec_hdr(const struct ubi_device *ubi, int pnum)
 	uint32_t crc, hdr_crc;
 	struct ubi_ec_hdr *ec_hdr;
 
+	if (!(ubi_chk_flags & UBI_CHK_IO))
+		return 0;
+
 	ec_hdr = kzalloc(ubi->ec_hdr_alsize, GFP_NOFS);
 	if (!ec_hdr)
 		return -ENOMEM;
@@ -1211,6 +1249,9 @@ static int paranoid_check_vid_hdr(const struct ubi_device *ubi, int pnum,
 	int err;
 	uint32_t magic;
 
+	if (!(ubi_chk_flags & UBI_CHK_IO))
+		return 0;
+
 	magic = be32_to_cpu(vid_hdr->magic);
 	if (magic != UBI_VID_HDR_MAGIC) {
 		ubi_err("bad VID header magic %#08x at PEB %d, must be %#08x",
@@ -1249,6 +1290,9 @@ static int paranoid_check_peb_vid_hdr(const struct ubi_device *ubi, int pnum)
 	struct ubi_vid_hdr *vid_hdr;
 	void *p;
 
+	if (!(ubi_chk_flags & UBI_CHK_IO))
+		return 0;
+
 	vid_hdr = ubi_zalloc_vid_hdr(ubi, GFP_NOFS);
 	if (!vid_hdr)
 		return -ENOMEM;
@@ -1294,15 +1338,26 @@ int ubi_dbg_check_write(struct ubi_device *ubi, const void *buf, int pnum,
 			int offset, int len)
 {
 	int err, i;
+	size_t read;
+	void *buf1;
+	loff_t addr = (loff_t)pnum * ubi->peb_size + offset;
 
-	mutex_lock(&ubi->dbg_buf_mutex);
-	err = ubi_io_read(ubi, ubi->dbg_peb_buf, pnum, offset, len);
-	if (err)
-		goto out_unlock;
+	if (!(ubi_chk_flags & UBI_CHK_IO))
+		return 0;
+
+	buf1 = __vmalloc(len, GFP_KERNEL | GFP_NOFS, PAGE_KERNEL);
+	if (!buf1) {
+		ubi_err("cannot allocate memory to check writes");
+		return 0;
+	}
+
+	err = ubi->mtd->read(ubi->mtd, addr, len, &read, buf1);
+	if (err && err != -EUCLEAN)
+		goto out_free;
 
 	for (i = 0; i < len; i++) {
 		uint8_t c = ((uint8_t *)buf)[i];
-		uint8_t c1 = ((uint8_t *)ubi->dbg_peb_buf)[i];
+		uint8_t c1 = ((uint8_t *)buf1)[i];
 		int dump_len;
 
 		if (c == c1)
@@ -1319,17 +1374,17 @@ int ubi_dbg_check_write(struct ubi_device *ubi, const void *buf, int pnum,
 		ubi_msg("hex dump of the read buffer from %d to %d",
 			i, i + dump_len);
 		print_hex_dump(KERN_DEBUG, "", DUMP_PREFIX_OFFSET, 32, 1,
-			       ubi->dbg_peb_buf + i, dump_len, 1);
+			       buf1 + i, dump_len, 1);
 		ubi_dbg_dump_stack();
 		err = -EINVAL;
-		goto out_unlock;
+		goto out_free;
 	}
-	mutex_unlock(&ubi->dbg_buf_mutex);
 
+	vfree(buf1);
 	return 0;
 
-out_unlock:
-	mutex_unlock(&ubi->dbg_buf_mutex);
+out_free:
+	vfree(buf1);
 	return err;
 }
 
@@ -1348,36 +1403,44 @@ int ubi_dbg_check_all_ff(struct ubi_device *ubi, int pnum, int offset, int len)
 {
 	size_t read;
 	int err;
+	void *buf;
 	loff_t addr = (loff_t)pnum * ubi->peb_size + offset;
 
-	mutex_lock(&ubi->dbg_buf_mutex);
-	err = ubi->mtd->read(ubi->mtd, addr, len, &read, ubi->dbg_peb_buf);
+	if (!(ubi_chk_flags & UBI_CHK_IO))
+		return 0;
+
+	buf = __vmalloc(len, GFP_KERNEL | GFP_NOFS, PAGE_KERNEL);
+	if (!buf) {
+		ubi_err("cannot allocate memory to check for 0xFFs");
+		return 0;
+	}
+
+	err = ubi->mtd->read(ubi->mtd, addr, len, &read, buf);
 	if (err && err != -EUCLEAN) {
 		ubi_err("error %d while reading %d bytes from PEB %d:%d, "
 			"read %zd bytes", err, len, pnum, offset, read);
 		goto error;
 	}
 
-	err = ubi_check_pattern(ubi->dbg_peb_buf, 0xFF, len);
+	err = ubi_check_pattern(buf, 0xFF, len);
 	if (err == 0) {
 		ubi_err("flash region at PEB %d:%d, length %d does not "
 			"contain all 0xFF bytes", pnum, offset, len);
 		goto fail;
 	}
-	mutex_unlock(&ubi->dbg_buf_mutex);
 
+	vfree(buf);
 	return 0;
 
 fail:
 	ubi_err("paranoid check failed for PEB %d", pnum);
 	ubi_msg("hex dump of the %d-%d region", offset, offset + len);
-	print_hex_dump(KERN_DEBUG, "", DUMP_PREFIX_OFFSET, 32, 1,
-		       ubi->dbg_peb_buf, len, 1);
+	print_hex_dump(KERN_DEBUG, "", DUMP_PREFIX_OFFSET, 32, 1, buf, len, 1);
 	err = -EINVAL;
 error:
 	ubi_dbg_dump_stack();
-	mutex_unlock(&ubi->dbg_buf_mutex);
+	vfree(buf);
 	return err;
 }
 
-#endif /* CONFIG_MTD_UBI_DEBUG_PARANOID */
+#endif /* CONFIG_MTD_UBI_DEBUG */

drivers/mtd/ubi/scan.c

@@ -39,32 +39,46 @@
  * eraseblocks are put to the @free list and the physical eraseblock to be
  * erased are put to the @erase list.
  *
+ * About corruptions
+ * ~~~~~~~~~~~~~~~~~
+ *
+ * UBI protects EC and VID headers with CRC-32 checksums, so it can detect
+ * whether the headers are corrupted or not. Sometimes UBI also protects the
+ * data with CRC-32, e.g., when it executes the atomic LEB change operation, or
+ * when it moves the contents of a PEB for wear-leveling purposes.
+ *
  * UBI tries to distinguish between 2 types of corruptions.
- * 1. Corruptions caused by power cuts. These are harmless and expected
- *    corruptions and UBI tries to handle them gracefully, without printing too
- *    many warnings and error messages. The idea is that we do not lose
- *    important data in these case - we may lose only the data which was being
- *    written to the media just before the power cut happened, and the upper
- *    layers (e.g., UBIFS) are supposed to handle these situations. UBI puts
- *    these PEBs to the head of the @erase list and they are scheduled for
- *    erasure.
+ *
+ * 1. Corruptions caused by power cuts. These are expected corruptions and UBI
+ * tries to handle them gracefully, without printing too many warnings and
+ * error messages. The idea is that we do not lose important data in these case
+ * - we may lose only the data which was being written to the media just before
+ * the power cut happened, and the upper layers (e.g., UBIFS) are supposed to
+ * handle such data losses (e.g., by using the FS journal).
+ *
+ * When UBI detects a corruption (CRC-32 mismatch) in a PEB, and it looks like
+ * the reason is a power cut, UBI puts this PEB to the @erase list, and all
+ * PEBs in the @erase list are scheduled for erasure later.
  *
  * 2. Unexpected corruptions which are not caused by power cuts. During
- *    scanning, such PEBs are put to the @corr list and UBI preserves them.
- *    Obviously, this lessens the amount of available PEBs, and if at some
- *    point UBI runs out of free PEBs, it switches to R/O mode. UBI also loudly
- *    informs about such PEBs every time the MTD device is attached.
+ * scanning, such PEBs are put to the @corr list and UBI preserves them.
+ * Obviously, this lessens the amount of available PEBs, and if at some  point
+ * UBI runs out of free PEBs, it switches to R/O mode. UBI also loudly informs
+ * about such PEBs every time the MTD device is attached.
  *
  * However, it is difficult to reliably distinguish between these types of
- * corruptions and UBI's strategy is as follows. UBI assumes (2.) if the VID
- * header is corrupted and the data area does not contain all 0xFFs, and there
- * were not bit-flips or integrity errors while reading the data area. Otherwise
- * UBI assumes (1.). The assumptions are:
- *   o if the data area contains only 0xFFs, there is no data, and it is safe
- *     to just erase this PEB.
- *   o if the data area has bit-flips and data integrity errors (ECC errors on
+ * corruptions and UBI's strategy is as follows. UBI assumes corruption type 2
+ * if the VID header is corrupted and the data area does not contain all 0xFFs,
+ * and there were no bit-flips or integrity errors while reading the data area.
+ * Otherwise UBI assumes corruption type 1. So the decision criteria are as
+ * follows.
+ *   o If the data area contains only 0xFFs, there is no data, and it is safe
+ *     to just erase this PEB - this is corruption type 1.
+ *   o If the data area has bit-flips or data integrity errors (ECC errors on
  *     NAND), it is probably a PEB which was being erased when power cut
- *     happened.
+ *     happened, so this is corruption type 1. However, this is just a guess,
+ *     which might be wrong.
+ *   o Otherwise this it corruption type 2.
  */
 
 #include <linux/err.h>
@@ -74,7 +88,7 @@
 #include <linux/random.h>
 #include "ubi.h"
 
-#ifdef CONFIG_MTD_UBI_DEBUG_PARANOID
+#ifdef CONFIG_MTD_UBI_DEBUG
 static int paranoid_check_si(struct ubi_device *ubi, struct ubi_scan_info *si);
 #else
 #define paranoid_check_si(ubi, si) 0
@@ -115,7 +129,7 @@ static int add_to_list(struct ubi_scan_info *si, int pnum, int ec, int to_head,
 	} else
 		BUG();
 
-	seb = kmalloc(sizeof(struct ubi_scan_leb), GFP_KERNEL);
+	seb = kmem_cache_alloc(si->scan_leb_slab, GFP_KERNEL);
 	if (!seb)
 		return -ENOMEM;
 
@@ -144,7 +158,7 @@ static int add_corrupted(struct ubi_scan_info *si, int pnum, int ec)
 
 	dbg_bld("add to corrupted: PEB %d, EC %d", pnum, ec);
 
-	seb = kmalloc(sizeof(struct ubi_scan_leb), GFP_KERNEL);
+	seb = kmem_cache_alloc(si->scan_leb_slab, GFP_KERNEL);
 	if (!seb)
 		return -ENOMEM;
 
@@ -553,7 +567,7 @@ int ubi_scan_add_used(struct ubi_device *ubi, struct ubi_scan_info *si,
 	if (err)
 		return err;
 
-	seb = kmalloc(sizeof(struct ubi_scan_leb), GFP_KERNEL);
+	seb = kmem_cache_alloc(si->scan_leb_slab, GFP_KERNEL);
 	if (!seb)
 		return -ENOMEM;
 
@@ -1152,9 +1166,15 @@ struct ubi_scan_info *ubi_scan(struct ubi_device *ubi)
 	si->volumes = RB_ROOT;
 
 	err = -ENOMEM;
+	si->scan_leb_slab = kmem_cache_create("ubi_scan_leb_slab",
+					      sizeof(struct ubi_scan_leb),
+					      0, 0, NULL);
+	if (!si->scan_leb_slab)
+		goto out_si;
+
 	ech = kzalloc(ubi->ec_hdr_alsize, GFP_KERNEL);
 	if (!ech)
-		goto out_si;
+		goto out_slab;
 
 	vidh = ubi_zalloc_vid_hdr(ubi, GFP_KERNEL);
 	if (!vidh)
@@ -1215,6 +1235,8 @@ struct ubi_scan_info *ubi_scan(struct ubi_device *ubi)
 	ubi_free_vid_hdr(ubi, vidh);
 out_ech:
 	kfree(ech);
+out_slab:
+	kmem_cache_destroy(si->scan_leb_slab);
 out_si:
 	ubi_scan_destroy_si(si);
 	return ERR_PTR(err);
@@ -1223,11 +1245,12 @@ struct ubi_scan_info *ubi_scan(struct ubi_device *ubi)
 /**
  * destroy_sv - free the scanning volume information
  * @sv: scanning volume information
+ * @si: scanning information
  *
  * This function destroys the volume RB-tree (@sv->root) and the scanning
  * volume information.
  */
-static void destroy_sv(struct ubi_scan_volume *sv)
+static void destroy_sv(struct ubi_scan_info *si, struct ubi_scan_volume *sv)
 {
 	struct ubi_scan_leb *seb;
 	struct rb_node *this = sv->root.rb_node;
@@ -1247,7 +1270,7 @@ static void destroy_sv(struct ubi_scan_volume *sv)
 					this->rb_right = NULL;
 			}
 
-			kfree(seb);
+			kmem_cache_free(si->scan_leb_slab, seb);
 		}
 	}
 	kfree(sv);
@@ -1265,19 +1288,19 @@ void ubi_scan_destroy_si(struct ubi_scan_info *si)
 
 	list_for_each_entry_safe(seb, seb_tmp, &si->alien, u.list) {
 		list_del(&seb->u.list);
-		kfree(seb);
+		kmem_cache_free(si->scan_leb_slab, seb);
 	}
 	list_for_each_entry_safe(seb, seb_tmp, &si->erase, u.list) {
 		list_del(&seb->u.list);
-		kfree(seb);
+		kmem_cache_free(si->scan_leb_slab, seb);
 	}
 	list_for_each_entry_safe(seb, seb_tmp, &si->corr, u.list) {
 		list_del(&seb->u.list);
-		kfree(seb);
+		kmem_cache_free(si->scan_leb_slab, seb);
 	}
 	list_for_each_entry_safe(seb, seb_tmp, &si->free, u.list) {
 		list_del(&seb->u.list);
-		kfree(seb);
+		kmem_cache_free(si->scan_leb_slab, seb);
 	}
 
 	/* Destroy the volume RB-tree */
@@ -1298,14 +1321,15 @@ void ubi_scan_destroy_si(struct ubi_scan_info *si)
 					rb->rb_right = NULL;
 			}
 
-			destroy_sv(sv);
+			destroy_sv(si, sv);
 		}
 	}
 
+	kmem_cache_destroy(si->scan_leb_slab);
 	kfree(si);
 }
 
-#ifdef CONFIG_MTD_UBI_DEBUG_PARANOID
+#ifdef CONFIG_MTD_UBI_DEBUG
 
 /**
  * paranoid_check_si - check the scanning information.
@@ -1323,6 +1347,9 @@ static int paranoid_check_si(struct ubi_device *ubi, struct ubi_scan_info *si)
 	struct ubi_scan_leb *seb, *last_seb;
 	uint8_t *buf;
 
+	if (!(ubi_chk_flags & UBI_CHK_GEN))
+		return 0;
+
 	/*
 	 * At first, check that scanning information is OK.
 	 */
@@ -1575,4 +1602,4 @@ static int paranoid_check_si(struct ubi_device *ubi, struct ubi_scan_info *si)
 	return -EINVAL;
 }
 
-#endif /* CONFIG_MTD_UBI_DEBUG_PARANOID */
+#endif /* CONFIG_MTD_UBI_DEBUG */

drivers/mtd/ubi/scan.h

@@ -109,6 +109,7 @@ struct ubi_scan_volume {
  * @mean_ec: mean erase counter value
  * @ec_sum: a temporary variable used when calculating @mean_ec
  * @ec_count: a temporary variable used when calculating @mean_ec
+ * @scan_leb_slab: slab cache for &struct ubi_scan_leb objects
  *
  * This data structure contains the result of scanning and may be used by other
  * UBI sub-systems to build final UBI data structures, further error-recovery
@@ -134,6 +135,7 @@ struct ubi_scan_info {
 	int mean_ec;
 	uint64_t ec_sum;
 	int ec_count;
+	struct kmem_cache *scan_leb_slab;
 };
 
 struct ubi_device;

drivers/mtd/ubi/ubi.h

@@ -40,6 +40,7 @@
 #include <linux/notifier.h>
 #include <linux/mtd/mtd.h>
 #include <linux/mtd/ubi.h>
+#include <asm/pgtable.h>
 
 #include "ubi-media.h"
 #include "scan.h"
@@ -387,8 +388,6 @@ struct ubi_wl_entry;
  * @peb_buf2: another buffer of PEB size used for different purposes
  * @buf_mutex: protects @peb_buf1 and @peb_buf2
  * @ckvol_mutex: serializes static volume checking when opening
- * @dbg_peb_buf: buffer of PEB size used for debugging
- * @dbg_buf_mutex: protects @dbg_peb_buf
  */
 struct ubi_device {
 	struct cdev cdev;
@@ -470,10 +469,6 @@ struct ubi_device {
 	void *peb_buf2;
 	struct mutex buf_mutex;
 	struct mutex ckvol_mutex;
-#ifdef CONFIG_MTD_UBI_DEBUG_PARANOID
-	void *dbg_peb_buf;
-	struct mutex dbg_buf_mutex;
-#endif
 };
 
 extern struct kmem_cache *ubi_wl_entry_slab;

drivers/mtd/ubi/vmt.c

@@ -28,7 +28,7 @@
 #include <linux/slab.h>
 #include "ubi.h"
 
-#ifdef CONFIG_MTD_UBI_DEBUG_PARANOID
+#ifdef CONFIG_MTD_UBI_DEBUG
 static int paranoid_check_volumes(struct ubi_device *ubi);
 #else
 #define paranoid_check_volumes(ubi) 0
@@ -711,7 +711,7 @@ void ubi_free_volume(struct ubi_device *ubi, struct ubi_volume *vol)
 	volume_sysfs_close(vol);
 }
 
-#ifdef CONFIG_MTD_UBI_DEBUG_PARANOID
+#ifdef CONFIG_MTD_UBI_DEBUG
 
 /**
  * paranoid_check_volume - check volume information.
@@ -876,6 +876,9 @@ static int paranoid_check_volumes(struct ubi_device *ubi)
 {
 	int i, err = 0;
 
+	if (!(ubi_chk_flags & UBI_CHK_GEN))
+		return 0;
+
 	for (i = 0; i < ubi->vtbl_slots; i++) {
 		err = paranoid_check_volume(ubi, i);
 		if (err)

drivers/mtd/ubi/vtbl.c

@@ -62,7 +62,7 @@
 #include <asm/div64.h>
 #include "ubi.h"
 
-#ifdef CONFIG_MTD_UBI_DEBUG_PARANOID
+#ifdef CONFIG_MTD_UBI_DEBUG
 static void paranoid_vtbl_check(const struct ubi_device *ubi);
 #else
 #define paranoid_vtbl_check(ubi)
@@ -868,7 +868,7 @@ int ubi_read_volume_table(struct ubi_device *ubi, struct ubi_scan_info *si)
 	return err;
 }
 
-#ifdef CONFIG_MTD_UBI_DEBUG_PARANOID
+#ifdef CONFIG_MTD_UBI_DEBUG
 
 /**
  * paranoid_vtbl_check - check volume table.
@@ -876,10 +876,13 @@ int ubi_read_volume_table(struct ubi_device *ubi, struct ubi_scan_info *si)
  */
 static void paranoid_vtbl_check(const struct ubi_device *ubi)
 {
+	if (!(ubi_chk_flags & UBI_CHK_GEN))
+		return;
+
 	if (vtbl_check(ubi, ubi->vtbl)) {
 		ubi_err("paranoid check failed");
 		BUG();
 	}
 }
 
-#endif /* CONFIG_MTD_UBI_DEBUG_PARANOID */
+#endif /* CONFIG_MTD_UBI_DEBUG */

drivers/mtd/ubi/wl.c

@@ -161,7 +161,7 @@ struct ubi_work {
 	int torture;
 };
 
-#ifdef CONFIG_MTD_UBI_DEBUG_PARANOID
+#ifdef CONFIG_MTD_UBI_DEBUG
 static int paranoid_check_ec(struct ubi_device *ubi, int pnum, int ec);
 static int paranoid_check_in_wl_tree(struct ubi_wl_entry *e,
 				     struct rb_root *root);
@@ -613,7 +613,7 @@ static void schedule_ubi_work(struct ubi_device *ubi, struct ubi_work *wrk)
 	list_add_tail(&wrk->list, &ubi->works);
 	ubi_assert(ubi->works_count >= 0);
 	ubi->works_count += 1;
-	if (ubi->thread_enabled)
+	if (ubi->thread_enabled && !ubi_dbg_is_bgt_disabled())
 		wake_up_process(ubi->bgt_thread);
 	spin_unlock(&ubi->wl_lock);
 }
@@ -1364,7 +1364,7 @@ int ubi_thread(void *u)
 
 		spin_lock(&ubi->wl_lock);
 		if (list_empty(&ubi->works) || ubi->ro_mode ||
-			       !ubi->thread_enabled) {
+		    !ubi->thread_enabled || ubi_dbg_is_bgt_disabled()) {
 			set_current_state(TASK_INTERRUPTIBLE);
 			spin_unlock(&ubi->wl_lock);
 			schedule();
@@ -1561,7 +1561,7 @@ void ubi_wl_close(struct ubi_device *ubi)
 	kfree(ubi->lookuptbl);
 }
 
-#ifdef CONFIG_MTD_UBI_DEBUG_PARANOID
+#ifdef CONFIG_MTD_UBI_DEBUG
 
 /**
  * paranoid_check_ec - make sure that the erase counter of a PEB is correct.
@@ -1578,6 +1578,9 @@ static int paranoid_check_ec(struct ubi_device *ubi, int pnum, int ec)
 	long long read_ec;
 	struct ubi_ec_hdr *ec_hdr;
 
+	if (!(ubi_chk_flags & UBI_CHK_GEN))
+		return 0;
+
 	ec_hdr = kzalloc(ubi->ec_hdr_alsize, GFP_NOFS);
 	if (!ec_hdr)
 		return -ENOMEM;
@@ -1614,6 +1617,9 @@ static int paranoid_check_ec(struct ubi_device *ubi, int pnum, int ec)
 static int paranoid_check_in_wl_tree(struct ubi_wl_entry *e,
 				     struct rb_root *root)
 {
+	if (!(ubi_chk_flags & UBI_CHK_GEN))
+		return 0;
+
 	if (in_wl_tree(e, root))
 		return 0;
 
@@ -1636,6 +1642,9 @@ static int paranoid_check_in_pq(struct ubi_device *ubi, struct ubi_wl_entry *e)
 	struct ubi_wl_entry *p;
 	int i;
 
+	if (!(ubi_chk_flags & UBI_CHK_GEN))
+		return 0;
+
 	for (i = 0; i < UBI_PROT_QUEUE_LEN; ++i)
 		list_for_each_entry(p, &ubi->pq[i], u.list)
 			if (p == e)
@@ -1646,4 +1655,5 @@ static int paranoid_check_in_pq(struct ubi_device *ubi, struct ubi_wl_entry *e)
 	ubi_dbg_dump_stack();
 	return -EINVAL;
 }
-#endif /* CONFIG_MTD_UBI_DEBUG_PARANOID */
+
+#endif /* CONFIG_MTD_UBI_DEBUG */