diff options
Diffstat (limited to 'drivers/mtd/ubi/wl.c')
| -rw-r--r-- | drivers/mtd/ubi/wl.c | 208 |
1 files changed, 102 insertions, 106 deletions
diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c index a471a491f0ab..05d70937b543 100644 --- a/drivers/mtd/ubi/wl.c +++ b/drivers/mtd/ubi/wl.c @@ -19,22 +19,22 @@ */ /* - * UBI wear-leveling unit. + * UBI wear-leveling sub-system. * - * This unit is responsible for wear-leveling. It works in terms of physical - * eraseblocks and erase counters and knows nothing about logical eraseblocks, - * volumes, etc. From this unit's perspective all physical eraseblocks are of - * two types - used and free. Used physical eraseblocks are those that were - * "get" by the 'ubi_wl_get_peb()' function, and free physical eraseblocks are - * those that were put by the 'ubi_wl_put_peb()' function. + * This sub-system is responsible for wear-leveling. It works in terms of + * physical* eraseblocks and erase counters and knows nothing about logical + * eraseblocks, volumes, etc. From this sub-system's perspective all physical + * eraseblocks are of two types - used and free. Used physical eraseblocks are + * those that were "get" by the 'ubi_wl_get_peb()' function, and free physical + * eraseblocks are those that were put by the 'ubi_wl_put_peb()' function. * * Physical eraseblocks returned by 'ubi_wl_get_peb()' have only erase counter - * header. The rest of the physical eraseblock contains only 0xFF bytes. + * header. The rest of the physical eraseblock contains only %0xFF bytes. * - * When physical eraseblocks are returned to the WL unit by means of the + * When physical eraseblocks are returned to the WL sub-system by means of the * 'ubi_wl_put_peb()' function, they are scheduled for erasure. The erasure is * done asynchronously in context of the per-UBI device background thread, - * which is also managed by the WL unit. + * which is also managed by the WL sub-system. * * The wear-leveling is ensured by means of moving the contents of used * physical eraseblocks with low erase counter to free physical eraseblocks @@ -43,34 +43,36 @@ * The 'ubi_wl_get_peb()' function accepts data type hints which help to pick * an "optimal" physical eraseblock. For example, when it is known that the * physical eraseblock will be "put" soon because it contains short-term data, - * the WL unit may pick a free physical eraseblock with low erase counter, and - * so forth. + * the WL sub-system may pick a free physical eraseblock with low erase + * counter, and so forth. * - * If the WL unit fails to erase a physical eraseblock, it marks it as bad. + * If the WL sub-system fails to erase a physical eraseblock, it marks it as + * bad. * - * This unit is also responsible for scrubbing. If a bit-flip is detected in a - * physical eraseblock, it has to be moved. Technically this is the same as - * moving it for wear-leveling reasons. + * This sub-system is also responsible for scrubbing. If a bit-flip is detected + * in a physical eraseblock, it has to be moved. Technically this is the same + * as moving it for wear-leveling reasons. * - * As it was said, for the UBI unit all physical eraseblocks are either "free" - * or "used". Free eraseblock are kept in the @wl->free RB-tree, while used - * eraseblocks are kept in a set of different RB-trees: @wl->used, + * As it was said, for the UBI sub-system all physical eraseblocks are either + * "free" or "used". Free eraseblock are kept in the @wl->free RB-tree, while + * used eraseblocks are kept in a set of different RB-trees: @wl->used, * @wl->prot.pnum, @wl->prot.aec, and @wl->scrub. * * Note, in this implementation, we keep a small in-RAM object for each physical * eraseblock. This is surely not a scalable solution. But it appears to be good * enough for moderately large flashes and it is simple. In future, one may - * re-work this unit and make it more scalable. + * re-work this sub-system and make it more scalable. * - * At the moment this unit does not utilize the sequence number, which was - * introduced relatively recently. But it would be wise to do this because the - * sequence number of a logical eraseblock characterizes how old is it. For + * At the moment this sub-system does not utilize the sequence number, which + * was introduced relatively recently. But it would be wise to do this because + * the sequence number of a logical eraseblock characterizes how old is it. For * example, when we move a PEB with low erase counter, and we need to pick the * target PEB, we pick a PEB with the highest EC if our PEB is "old" and we * pick target PEB with an average EC if our PEB is not very "old". This is a - * room for future re-works of the WL unit. + * room for future re-works of the WL sub-system. * - * FIXME: looks too complex, should be simplified (later). + * Note: the stuff with protection trees looks too complex and is difficult to + * understand. Should be fixed. */ #include <linux/slab.h> @@ -92,20 +94,21 @@ /* * Maximum difference between two erase counters. If this threshold is - * exceeded, the WL unit starts moving data from used physical eraseblocks with - * low erase counter to free physical eraseblocks with high erase counter. + * exceeded, the WL sub-system starts moving data from used physical + * eraseblocks with low erase counter to free physical eraseblocks with high + * erase counter. */ #define UBI_WL_THRESHOLD CONFIG_MTD_UBI_WL_THRESHOLD /* - * When a physical eraseblock is moved, the WL unit has to pick the target + * When a physical eraseblock is moved, the WL sub-system has to pick the target * physical eraseblock to move to. The simplest way would be just to pick the * one with the highest erase counter. But in certain workloads this could lead * to an unlimited wear of one or few physical eraseblock. Indeed, imagine a * situation when the picked physical eraseblock is constantly erased after the * data is written to it. So, we have a constant which limits the highest erase - * counter of the free physical eraseblock to pick. Namely, the WL unit does - * not pick eraseblocks with erase counter greater then the lowest erase + * counter of the free physical eraseblock to pick. Namely, the WL sub-system + * does not pick eraseblocks with erase counter greater then the lowest erase * counter plus %WL_FREE_MAX_DIFF. */ #define WL_FREE_MAX_DIFF (2*UBI_WL_THRESHOLD) @@ -123,11 +126,11 @@ * @abs_ec: the absolute erase counter value when the protection ends * @e: the wear-leveling entry of the physical eraseblock under protection * - * When the WL unit returns a physical eraseblock, the physical eraseblock is - * protected from being moved for some "time". For this reason, the physical - * eraseblock is not directly moved from the @wl->free tree to the @wl->used - * tree. There is one more tree in between where this physical eraseblock is - * temporarily stored (@wl->prot). + * When the WL sub-system returns a physical eraseblock, the physical + * eraseblock is protected from being moved for some "time". For this reason, + * the physical eraseblock is not directly moved from the @wl->free tree to the + * @wl->used tree. There is one more tree in between where this physical + * eraseblock is temporarily stored (@wl->prot). * * All this protection stuff is needed because: * o we don't want to move physical eraseblocks just after we have given them @@ -175,7 +178,6 @@ struct ubi_wl_prot_entry { * @list: a link in the list of pending works * @func: worker function * @priv: private data of the worker function - * * @e: physical eraseblock to erase * @torture: if the physical eraseblock has to be tortured * @@ -473,52 +475,47 @@ retry: } switch (dtype) { - case UBI_LONGTERM: - /* - * For long term data we pick a physical eraseblock - * with high erase counter. But the highest erase - * counter we can pick is bounded by the the lowest - * erase counter plus %WL_FREE_MAX_DIFF. - */ - e = find_wl_entry(&ubi->free, WL_FREE_MAX_DIFF); - protect = LT_PROTECTION; - break; - case UBI_UNKNOWN: - /* - * For unknown data we pick a physical eraseblock with - * medium erase counter. But we by no means can pick a - * physical eraseblock with erase counter greater or - * equivalent than the lowest erase counter plus - * %WL_FREE_MAX_DIFF. - */ - first = rb_entry(rb_first(&ubi->free), - struct ubi_wl_entry, rb); - last = rb_entry(rb_last(&ubi->free), - struct ubi_wl_entry, rb); + case UBI_LONGTERM: + /* + * For long term data we pick a physical eraseblock with high + * erase counter. But the highest erase counter we can pick is + * bounded by the the lowest erase counter plus + * %WL_FREE_MAX_DIFF. + */ + e = find_wl_entry(&ubi->free, WL_FREE_MAX_DIFF); + protect = LT_PROTECTION; + break; + case UBI_UNKNOWN: + /* + * For unknown data we pick a physical eraseblock with medium + * erase counter. But we by no means can pick a physical + * eraseblock with erase counter greater or equivalent than the + * lowest erase counter plus %WL_FREE_MAX_DIFF. + */ + first = rb_entry(rb_first(&ubi->free), struct ubi_wl_entry, rb); + last = rb_entry(rb_last(&ubi->free), struct ubi_wl_entry, rb); - if (last->ec - first->ec < WL_FREE_MAX_DIFF) - e = rb_entry(ubi->free.rb_node, - struct ubi_wl_entry, rb); - else { - medium_ec = (first->ec + WL_FREE_MAX_DIFF)/2; - e = find_wl_entry(&ubi->free, medium_ec); - } - protect = U_PROTECTION; - break; - case UBI_SHORTTERM: - /* - * For short term data we pick a physical eraseblock - * with the lowest erase counter as we expect it will - * be erased soon. - */ - e = rb_entry(rb_first(&ubi->free), - struct ubi_wl_entry, rb); - protect = ST_PROTECTION; - break; - default: - protect = 0; - e = NULL; - BUG(); + if (last->ec - first->ec < WL_FREE_MAX_DIFF) + e = rb_entry(ubi->free.rb_node, + struct ubi_wl_entry, rb); + else { + medium_ec = (first->ec + WL_FREE_MAX_DIFF)/2; + e = find_wl_entry(&ubi->free, medium_ec); + } + protect = U_PROTECTION; + break; + case UBI_SHORTTERM: + /* + * For short term data we pick a physical eraseblock with the + * lowest erase counter as we expect it will be erased soon. + */ + e = rb_entry(rb_first(&ubi->free), struct ubi_wl_entry, rb); + protect = ST_PROTECTION; + break; + default: + protect = 0; + e = NULL; + BUG(); } /* @@ -582,7 +579,8 @@ found: * This function returns zero in case of success and a negative error code in * case of failure. */ -static int sync_erase(struct ubi_device *ubi, struct ubi_wl_entry *e, int torture) +static int sync_erase(struct ubi_device *ubi, struct ubi_wl_entry *e, + int torture) { int err; struct ubi_ec_hdr *ec_hdr; @@ -634,8 +632,7 @@ out_free: } /** - * check_protection_over - check if it is time to stop protecting some - * physical eraseblocks. + * check_protection_over - check if it is time to stop protecting some PEBs. * @ubi: UBI device description object * * This function is called after each erase operation, when the absolute erase @@ -871,6 +868,10 @@ static int wear_leveling_worker(struct ubi_device *ubi, struct ubi_work *wrk, } ubi_free_vid_hdr(ubi, vid_hdr); + if (scrubbing && !protect) + ubi_msg("scrubbed PEB %d, data moved to PEB %d", + e1->pnum, e2->pnum); + spin_lock(&ubi->wl_lock); if (protect) prot_tree_add(ubi, e1, pe, protect); @@ -1054,8 +1055,8 @@ static int erase_worker(struct ubi_device *ubi, struct ubi_work *wl_wrk, spin_unlock(&ubi->wl_lock); /* - * One more erase operation has happened, take care about protected - * physical eraseblocks. + * One more erase operation has happened, take care about + * protected physical eraseblocks. */ check_protection_over(ubi); @@ -1136,7 +1137,7 @@ out_ro: } /** - * ubi_wl_put_peb - return a physical eraseblock to the wear-leveling unit. + * ubi_wl_put_peb - return a PEB to the wear-leveling sub-system. * @ubi: UBI device description object * @pnum: physical eraseblock to return * @torture: if this physical eraseblock has to be tortured @@ -1175,11 +1176,11 @@ retry: /* * User is putting the physical eraseblock which was selected * as the target the data is moved to. It may happen if the EBA - * unit already re-mapped the LEB in 'ubi_eba_copy_leb()' but - * the WL unit has not put the PEB to the "used" tree yet, but - * it is about to do this. So we just set a flag which will - * tell the WL worker that the PEB is not needed anymore and - * should be scheduled for erasure. + * sub-system already re-mapped the LEB in 'ubi_eba_copy_leb()' + * but the WL sub-system has not put the PEB to the "used" tree + * yet, but it is about to do this. So we just set a flag which + * will tell the WL worker that the PEB is not needed anymore + * and should be scheduled for erasure. */ dbg_wl("PEB %d is the target of data moving", pnum); ubi_assert(!ubi->move_to_put); @@ -1229,7 +1230,7 @@ int ubi_wl_scrub_peb(struct ubi_device *ubi, int pnum) { struct ubi_wl_entry *e; - ubi_msg("schedule PEB %d for scrubbing", pnum); + dbg_msg("schedule PEB %d for scrubbing", pnum); retry: spin_lock(&ubi->wl_lock); @@ -1368,7 +1369,7 @@ int ubi_thread(void *u) int err; if (kthread_should_stop()) - goto out; + break; if (try_to_freeze()) continue; @@ -1403,7 +1404,6 @@ int ubi_thread(void *u) cond_resched(); } -out: dbg_wl("background thread \"%s\" is killed", ubi->bgt_name); return 0; } @@ -1426,8 +1426,7 @@ static void cancel_pending(struct ubi_device *ubi) } /** - * ubi_wl_init_scan - initialize the wear-leveling unit using scanning - * information. + * ubi_wl_init_scan - initialize the WL sub-system using scanning information. * @ubi: UBI device description object * @si: scanning information * @@ -1584,13 +1583,12 @@ static void protection_trees_destroy(struct ubi_device *ubi) } /** - * ubi_wl_close - close the wear-leveling unit. + * ubi_wl_close - close the wear-leveling sub-system. * @ubi: UBI device description object */ void ubi_wl_close(struct ubi_device *ubi) { - dbg_wl("close the UBI wear-leveling unit"); - + dbg_wl("close the WL sub-system"); cancel_pending(ubi); protection_trees_destroy(ubi); tree_destroy(&ubi->used); @@ -1602,8 +1600,7 @@ void ubi_wl_close(struct ubi_device *ubi) #ifdef CONFIG_MTD_UBI_DEBUG_PARANOID /** - * paranoid_check_ec - make sure that the erase counter of a physical eraseblock - * is correct. + * paranoid_check_ec - make sure that the erase counter of a PEB is correct. * @ubi: UBI device description object * @pnum: the physical eraseblock number to check * @ec: the erase counter to check @@ -1644,13 +1641,12 @@ out_free: } /** - * paranoid_check_in_wl_tree - make sure that a wear-leveling entry is present - * in a WL RB-tree. + * paranoid_check_in_wl_tree - check that wear-leveling entry is in WL RB-tree. * @e: the wear-leveling entry to check * @root: the root of the tree * - * This function returns zero if @e is in the @root RB-tree and %1 if it - * is not. + * This function returns zero if @e is in the @root RB-tree and %1 if it is + * not. */ static int paranoid_check_in_wl_tree(struct ubi_wl_entry *e, struct rb_root *root) |