diff options
Diffstat (limited to 'drivers/mtd/ubi/scan.c')
| -rw-r--r-- | drivers/mtd/ubi/scan.c | 111 |
1 files changed, 55 insertions, 56 deletions
diff --git a/drivers/mtd/ubi/scan.c b/drivers/mtd/ubi/scan.c index 06a2d706213..93257f3c25d 100644 --- a/drivers/mtd/ubi/scan.c +++ b/drivers/mtd/ubi/scan.c @@ -19,21 +19,21 @@ */ /* - * UBI scanning sub-system. + * UBI attaching sub-system. * - * This sub-system is responsible for scanning the flash media, checking UBI - * headers and providing complete information about the UBI flash image. + * This sub-system is responsible for attaching MTD devices and it also + * implements flash media scanning. * * The attaching information is represented by a &struct ubi_attach_info' - * object. Information about found volumes is represented by - * &struct ubi_ainf_volume objects which are kept in volume RB-tree with root - * at the @volumes field. The RB-tree is indexed by the volume ID. + * object. Information about volumes is represented by &struct ubi_ainf_volume + * objects which are kept in volume RB-tree with root at the @volumes field. + * The RB-tree is indexed by the volume ID. * - * Scanned logical eraseblocks are represented by &struct ubi_ainf_peb objects. - * These objects are kept in per-volume RB-trees with the root at the - * corresponding &struct ubi_ainf_volume object. To put it differently, we keep - * an RB-tree of per-volume objects and each of these objects is the root of - * RB-tree of per-eraseblock objects. + * Logical eraseblocks are represented by &struct ubi_ainf_peb objects. These + * objects are kept in per-volume RB-trees with the root at the corresponding + * &struct ubi_ainf_volume object. To put it differently, we keep an RB-tree of + * per-volume objects and each of these objects is the root of RB-tree of + * per-LEB objects. * * Corrupted physical eraseblocks are put to the @corr list, free physical * eraseblocks are put to the @free list and the physical eraseblock to be @@ -51,28 +51,29 @@ * * 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). + * error messages. The idea is that we do not lose important data in these + * cases - we may lose only the data which were 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. + * attaching, 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 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 + * corruptions and UBI's strategy is as follows (in case of attaching by + * scanning). 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 (e.g., ECC errors in case of NAND) 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 are 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 @@ -102,7 +103,8 @@ static struct ubi_vid_hdr *vidh; * @to_head: if not zero, add to the head of the list * @list: the list to add to * - * This function adds physical eraseblock @pnum to free, erase, or alien lists. + * This function allocates a 'struct ubi_ainf_peb' object for physical + * eraseblock @pnum and adds it to the "free", "erase", or "alien" lists. * If @to_head is not zero, PEB will be added to the head of the list, which * basically means it will be processed first later. E.g., we add corrupted * PEBs (corrupted due to power cuts) to the head of the erase list to make @@ -144,9 +146,10 @@ static int add_to_list(struct ubi_attach_info *ai, int pnum, int ec, * @pnum: physical eraseblock number to add * @ec: erase counter of the physical eraseblock * - * This function adds corrupted physical eraseblock @pnum to the 'corr' list. - * The corruption was presumably not caused by a power cut. Returns zero in - * case of success and a negative error code in case of failure. + * This function allocates a 'struct ubi_ainf_peb' object for a corrupted + * physical eraseblock @pnum and adds it to the 'corr' list. The corruption + * was presumably not caused by a power cut. Returns zero in case of success + * and a negative error code in case of failure. */ static int add_corrupted(struct ubi_attach_info *ai, int pnum, int ec) { @@ -241,8 +244,8 @@ bad: * If the volume corresponding to the @vid_hdr logical eraseblock is already * present in the attaching information, this function does nothing. Otherwise * it adds corresponding volume to the attaching information. Returns a pointer - * to the scanning volume object in case of success and a negative error code - * in case of failure. + * to the allocated "av" object in case of success and a negative error code in + * case of failure. */ static struct ubi_ainf_volume *add_volume(struct ubi_attach_info *ai, int vol_id, int pnum, @@ -425,7 +428,7 @@ out_free_vidh: } /** - * ubi_add_to_av - add physical eraseblock to the attaching information. + * ubi_add_to_av - add used physical eraseblock to the attaching information. * @ubi: UBI device description object * @ai: attaching information * @pnum: the physical eraseblock number @@ -692,8 +695,8 @@ out_free: * the lists, writes the EC header if it is needed, and removes it from the * list. * - * This function returns scanning physical eraseblock information in case of - * success and an error code in case of failure. + * This function returns a pointer to the "aeb" of the found free PEB in case + * of success and an error code in case of failure. */ struct ubi_ainf_peb *ubi_early_get_peb(struct ubi_device *ubi, struct ubi_attach_info *ai) @@ -793,16 +796,18 @@ out_unlock: } /** - * process_eb - read, check UBI headers, and add them to attaching information. + * scan_peb - scan and process UBI headers of a PEB. * @ubi: UBI device description object * @ai: attaching information * @pnum: the physical eraseblock number * - * This function returns a zero if the physical eraseblock was successfully - * handled and a negative error code in case of failure. + * This function reads UBI headers of PEB @pnum, checks them, and adds + * information about this PEB to the corresponding list or RB-tree in the + * "attaching info" structure. Returns zero if the physical eraseblock was + * successfully handled and a negative error code in case of failure. */ -static int process_eb(struct ubi_device *ubi, struct ubi_attach_info *ai, - int pnum) +static int scan_peb(struct ubi_device *ubi, struct ubi_attach_info *ai, + int pnum) { long long uninitialized_var(ec); int err, bitflips = 0, vol_id, ec_err = 0; @@ -814,11 +819,6 @@ static int process_eb(struct ubi_device *ubi, struct ubi_attach_info *ai, if (err < 0) return err; else if (err) { - /* - * FIXME: this is actually duty of the I/O sub-system to - * initialize this, but MTD does not provide enough - * information. - */ ai->bad_peb_count += 1; return 0; } @@ -1033,18 +1033,17 @@ adjust_mean_ec: } /** - * check_what_we_have - check what PEB were found by scanning. + * late_analysis - analyze the overall situation with PEB. * @ubi: UBI device description object * @ai: attaching information * - * This is a helper function which takes a look what PEBs were found by - * scanning, and decides whether the flash is empty and should be formatted and - * whether there are too many corrupted PEBs and we should not attach this - * MTD device. Returns zero if we should proceed with attaching the MTD device, - * and %-EINVAL if we should not. + * This is a helper function which takes a look what PEBs we have after we + * gather information about all of them ("ai" is compete). It decides whether + * the flash is empty and should be formatted of whether there are too many + * corrupted PEBs and we should not attach this MTD device. Returns zero if we + * should proceed with attaching the MTD device, and %-EINVAL if we should not. */ -static int check_what_we_have(struct ubi_device *ubi, - struct ubi_attach_info *ai) +static int late_analysis(struct ubi_device *ubi, struct ubi_attach_info *ai) { struct ubi_ainf_peb *aeb; int max_corr, peb_count; @@ -1112,7 +1111,8 @@ static int check_what_we_have(struct ubi_device *ubi, * @ubi: UBI device description object * * This function does full scanning of an MTD device and returns complete - * information about it. In case of failure, an error code is returned. + * information about it in form of a "struct ubi_attach_info" object. In case + * of failure, an error code is returned. */ struct ubi_attach_info *ubi_scan(struct ubi_device *ubi) { @@ -1151,7 +1151,7 @@ struct ubi_attach_info *ubi_scan(struct ubi_device *ubi) cond_resched(); dbg_gen("process PEB %d", pnum); - err = process_eb(ubi, ai, pnum); + err = scan_peb(ubi, ai, pnum); if (err < 0) goto out_vidh; } @@ -1162,7 +1162,7 @@ struct ubi_attach_info *ubi_scan(struct ubi_device *ubi) if (ai->ec_count) ai->mean_ec = div_u64(ai->ec_sum, ai->ec_count); - err = check_what_we_have(ubi, ai); + err = late_analysis(ubi, ai); if (err) goto out_vidh; @@ -1208,12 +1208,11 @@ out_ai: } /** - * destroy_av - free the scanning volume information - * @av: scanning volume information + * destroy_av - free volume attaching information. + * @av: volume attaching information * @ai: attaching information * - * This function destroys the volume RB-tree (@av->root) and the scanning - * volume information. + * This function destroys the volume attaching information. */ static void destroy_av(struct ubi_attach_info *ai, struct ubi_ainf_volume *av) { |