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UBI: fix atomic LEB change problems

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When the UBI device is nearly full, i.e. all LEBs are mapped, we have
only one spare LEB left - the one we reserved for WL purposes. Well,
I do not count the LEBs which were reserved for bad PEB handling -
suppose NOR flash for simplicity. If an "atomic LEB change operation"
is run, and the WL unit is moving a LEB, we have no spare LEBs to
finish the operation and fail, which is not good. Moreover, if there
are 2 or more simultanious "atomic LEB change" requests, only one of
them has chances to succeed, the other will fail with -ENOSPC. Not
good either.

This patch does 2 things:
1. Reserves one PEB for the "atomic LEB change" operation.
2. Serealize the operations so that only on of them may run
   at a time (by means of a mutex).

Pointed-to-by: Brijesh Singh <brijesh.s.singh@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This commit is contained in:
Artem Bityutskiy 2007-09-13 14:28:14 +03:00
parent 6986646ba7
commit e8823bd63d
2 changed files with 33 additions and 21 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

48
drivers/mtd/ubi/eba.c
View file

@ -46,6 +46,9 @@
#include <linux/err.h>
#include "ubi.h"
/* Number of physical eraseblocks reserved for atomic LEB change operation */
#define EBA_RESERVED_PEBS 1
/**
* struct ltree_entry - an entry in the lock tree.
* @rb: links RB-tree nodes
@ -827,6 +830,9 @@ int ubi_eba_write_leb_st(struct ubi_device *ubi, int vol_id, int lnum,
* data, which has to be aligned. This function guarantees that in case of an
* unclean reboot the old contents is preserved. Returns zero in case of
* success and a negative error code in case of failure.
*
* UBI reserves one LEB for the "atomic LEB change" operation, so only one
* LEB change may be done at a time. This is ensured by @ubi->alc_mutex.
*/
int ubi_eba_atomic_leb_change(struct ubi_device *ubi, int vol_id, int lnum,
const void *buf, int len, int dtype)
@ -843,11 +849,10 @@ int ubi_eba_atomic_leb_change(struct ubi_device *ubi, int vol_id, int lnum,
if (!vid_hdr)
return -ENOMEM;
mutex_lock(&ubi->alc_mutex);
err = leb_write_lock(ubi, vol_id, lnum);
if (err) {
ubi_free_vid_hdr(ubi, vid_hdr);
return err;
}
if (err)
goto out_mutex;
vid_hdr->sqnum = cpu_to_be64(next_sqnum(ubi));
vid_hdr->vol_id = cpu_to_be32(vol_id);
@ -864,9 +869,8 @@ int ubi_eba_atomic_leb_change(struct ubi_device *ubi, int vol_id, int lnum,
retry:
pnum = ubi_wl_get_peb(ubi, dtype);
if (pnum < 0) {
ubi_free_vid_hdr(ubi, vid_hdr);
leb_write_unlock(ubi, vol_id, lnum);
return pnum;
err = pnum;
goto out_leb_unlock;
}
dbg_eba("change LEB %d:%d, PEB %d, write VID hdr to PEB %d",
@ -888,17 +892,18 @@ int ubi_eba_atomic_leb_change(struct ubi_device *ubi, int vol_id, int lnum,
if (vol->eba_tbl[lnum] >= 0) {
err = ubi_wl_put_peb(ubi, vol->eba_tbl[lnum], 1);
if (err) {
ubi_free_vid_hdr(ubi, vid_hdr);
leb_write_unlock(ubi, vol_id, lnum);
return err;
}
if (err)
goto out_leb_unlock;
}
vol->eba_tbl[lnum] = pnum;
out_leb_unlock:
leb_write_unlock(ubi, vol_id, lnum);
out_mutex:
mutex_unlock(&ubi->alc_mutex);
ubi_free_vid_hdr(ubi, vid_hdr);
return 0;
return err;
write_error:
if (err != -EIO || !ubi->bad_allowed) {
@ -908,17 +913,13 @@ int ubi_eba_atomic_leb_change(struct ubi_device *ubi, int vol_id, int lnum,
* mode just in case.
*/
ubi_ro_mode(ubi);
leb_write_unlock(ubi, vol_id, lnum);
ubi_free_vid_hdr(ubi, vid_hdr);
return err;
goto out_leb_unlock;
}
err = ubi_wl_put_peb(ubi, pnum, 1);
if (err || ++tries > UBI_IO_RETRIES) {
ubi_ro_mode(ubi);
leb_write_unlock(ubi, vol_id, lnum);
ubi_free_vid_hdr(ubi, vid_hdr);
return err;
goto out_leb_unlock;
}
vid_hdr->sqnum = cpu_to_be64(next_sqnum(ubi));
@ -1122,6 +1123,7 @@ int ubi_eba_init_scan(struct ubi_device *ubi, struct ubi_scan_info *si)
dbg_eba("initialize EBA unit");
spin_lock_init(&ubi->ltree_lock);
mutex_init(&ubi->alc_mutex);
ubi->ltree = RB_ROOT;
if (ubi_devices_cnt == 0) {
@ -1183,6 +1185,14 @@ int ubi_eba_init_scan(struct ubi_device *ubi, struct ubi_scan_info *si)
ubi->rsvd_pebs += ubi->beb_rsvd_pebs;
}
if (ubi->avail_pebs < EBA_RESERVED_PEBS) {
ubi_err("no enough physical eraseblocks (%d, need %d)",
ubi->avail_pebs, EBA_RESERVED_PEBS);
goto out_free;
}
ubi->avail_pebs -= EBA_RESERVED_PEBS;
ubi->rsvd_pebs += EBA_RESERVED_PEBS;
dbg_eba("EBA unit is initialized");
return 0;

6
drivers/mtd/ubi/ubi.h
View file

@ -221,14 +221,15 @@ struct ubi_wl_entry;
* @vtbl_slots: how many slots are available in the volume table
* @vtbl_size: size of the volume table in bytes
* @vtbl: in-RAM volume table copy
* @vtbl_mutex: protects on-flash volume table
*
* @max_ec: current highest erase counter value
* @mean_ec: current mean erase counter value
*
* global_sqnum: global sequence number
* @global_sqnum: global sequence number
* @ltree_lock: protects the lock tree and @global_sqnum
* @ltree: the lock tree
* @vtbl_mutex: protects on-flash volume table
* @alc_mutex: serializes "atomic LEB change" operations
*
* @used: RB-tree of used physical eraseblocks
* @free: RB-tree of free physical eraseblocks
@ -308,6 +309,7 @@ struct ubi_device {
unsigned long long global_sqnum;
spinlock_t ltree_lock;
struct rb_root ltree;
struct mutex alc_mutex;
/* Wear-leveling unit's stuff */
struct rb_root used;