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Commit fbd0107f authored by Artem Bityutskiy's avatar Artem Bityutskiy
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UBI: amend comments after all the renamings 

This patch amends commentaries in scan.[ch] to match the new logic. Reminder -
we did the restructuring to prepare the code for adding the fastmap. This patch
also renames a couple of functions - it was too difficult to separate out that
change and I decided that it is not too bad to have it in the same patch with
commentaries changes.
Signed-off-by: default avatarArtem Bityutskiy <artem.bityutskiy@linux.intel.com>
parent 1fc2e3e5
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Showing with 73 additions and 81 deletions
drivers/mtd/ubi/build.c
View file @ fbd0107f
......@@ -27,10 +27,6 @@
* module load parameters or the kernel boot parameters. If MTD devices were
* specified, UBI does not attach any MTD device, but it is possible to do
* later using the "UBI control device".
*
* At the moment we only attach UBI devices by scanning, which will become a
* bottleneck when flashes reach certain large size. Then one may improve UBI
* and add other methods, although it does not seem to be easy to do.
*/
#include <linux/err.h>
......@@ -790,11 +786,11 @@ static int io_init(struct ubi_device *ubi)
ubi_msg("data offset: %d", ubi->leb_start);
/*
* Note, ideally, we have to initialize ubi->bad_peb_count here. But
* Note, ideally, we have to initialize @ubi->bad_peb_count here. But
* unfortunately, MTD does not provide this information. We should loop
* over all physical eraseblocks and invoke mtd->block_is_bad() for
* each physical eraseblock. So, we skip ubi->bad_peb_count
* uninitialized and initialize it after scanning.
* each physical eraseblock. So, we leave @ubi->bad_peb_count
* uninitialized so far.
*/
return 0;
......@@ -805,7 +801,7 @@ static int io_init(struct ubi_device *ubi)
* @ubi: UBI device description object
* @vol_id: ID of the volume to re-size
*
* This function re-sizes the volume marked by the @UBI_VTBL_AUTORESIZE_FLG in
* This function re-sizes the volume marked by the %UBI_VTBL_AUTORESIZE_FLG in
* the volume table to the largest possible size. See comments in ubi-header.h
* for more description of the flag. Returns zero in case of success and a
* negative error code in case of failure.
......
drivers/mtd/ubi/io.c
View file @ fbd0107f
......@@ -513,8 +513,7 @@ static int nor_erase_prepare(struct ubi_device *ubi, int pnum)
* It is important to first invalidate the EC header, and then the VID
* header. Otherwise a power cut may lead to valid EC header and
* invalid VID header, in which case UBI will treat this PEB as
* corrupted and will try to preserve it, and print scary warnings (see
* the header comment in scan.c for more information).
* corrupted and will try to preserve it, and print scary warnings.
*/
addr = (loff_t)pnum * ubi->peb_size;
err = mtd_write(ubi->mtd, addr, 4, &written, (void *)&data);
......
drivers/mtd/ubi/scan.c
View file @ fbd0107f
......@@ -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 @@ static int validate_vid_hdr(const struct ubi_vid_hdr *vid_hdr,
* 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 @@ static int compare_lebs(struct ubi_device *ubi, const struct ubi_ainf_peb *aeb,
}
/**
* 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 @@ static int early_erase_peb(struct ubi_device *ubi,
* 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 @@ static int check_corruption(struct ubi_device *ubi, struct ubi_vid_hdr *vid_hdr,
}
/**
* 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 @@ static int process_eb(struct ubi_device *ubi, struct ubi_attach_info *ai,
}
/**
* 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 @@ struct ubi_attach_info *ubi_scan(struct ubi_device *ubi)
}
/**
* 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)
{
......
drivers/mtd/ubi/scan.h
View file @ fbd0107f
......@@ -146,7 +146,7 @@ struct ubi_vid_hdr;
* ubi_move_aeb_to_list - move a PEB from the volume tree to a list.
*
* @av: volume attaching information
* @aeb: scanning eraseblock information
* @aeb: attaching eraseblock information
* @list: the list to move to
*/
static inline void ubi_move_aeb_to_list(struct ubi_ainf_volume *av,
......
drivers/mtd/ubi/ubi-media.h
View file @ fbd0107f
......@@ -149,10 +149,10 @@ enum {
* The @image_seq field is used to validate a UBI image that has been prepared
* for a UBI device. The @image_seq value can be any value, but it must be the
* same on all eraseblocks. UBI will ensure that all new erase counter headers
* also contain this value, and will check the value when scanning at start-up.
* also contain this value, and will check the value when attaching the flash.
* One way to make use of @image_seq is to increase its value by one every time
* an image is flashed over an existing image, then, if the flashing does not
* complete, UBI will detect the error when scanning.
* complete, UBI will detect the error when attaching the media.
*/
struct ubi_ec_hdr {
__be32 magic;
......
drivers/mtd/ubi/vtbl.c
View file @ fbd0107f
......@@ -37,16 +37,15 @@
* LEB 1. This scheme guarantees recoverability from unclean reboots.
*
* In this UBI implementation the on-flash volume table does not contain any
* information about how many data static volumes contain. This information may
* be found from the scanning data.
* information about how much data static volumes contain.
*
* But it would still be beneficial to store this information in the volume
* table. For example, suppose we have a static volume X, and all its physical
* eraseblocks became bad for some reasons. Suppose we are attaching the
* corresponding MTD device, the scanning has found no logical eraseblocks
* corresponding MTD device, for some reason we find no logical eraseblocks
* corresponding to the volume X. According to the volume table volume X does
* exist. So we don't know whether it is just empty or all its physical
* eraseblocks went bad. So we cannot alarm the user about this corruption.
* eraseblocks went bad. So we cannot alarm the user properly.
*
* The volume table also stores so-called "update marker", which is used for
* volume updates. Before updating the volume, the update marker is set, and
......@@ -702,16 +701,16 @@ static int check_av(const struct ubi_volume *vol,
}
/**
* check_scanning_info - check that attaching information.
* check_attaching_info - check that attaching information.
* @ubi: UBI device description object
* @ai: attaching information
*
* Even though we protect on-flash data by CRC checksums, we still don't trust
* the media. This function ensures that attaching information is consistent to
* the information read from the volume table. Returns zero if the scanning
* the information read from the volume table. Returns zero if the attaching
* information is OK and %-EINVAL if it is not.
*/
static int check_scanning_info(const struct ubi_device *ubi,
static int check_attaching_info(const struct ubi_device *ubi,
struct ubi_attach_info *ai)
{
int err, i;
......@@ -719,15 +718,14 @@ static int check_scanning_info(const struct ubi_device *ubi,
struct ubi_volume *vol;
if (ai->vols_found > UBI_INT_VOL_COUNT + ubi->vtbl_slots) {
ubi_err("scanning found %d volumes, maximum is %d + %d",
ubi_err("found %d volumes while attaching, maximum is %d + %d",
ai->vols_found, UBI_INT_VOL_COUNT, ubi->vtbl_slots);
return -EINVAL;
}
if (ai->highest_vol_id >= ubi->vtbl_slots + UBI_INT_VOL_COUNT &&
ai->highest_vol_id < UBI_INTERNAL_VOL_START) {
ubi_err("too large volume ID %d found by scanning",
ai->highest_vol_id);
ubi_err("too large volume ID %d found", ai->highest_vol_id);
return -EINVAL;
}
......@@ -749,7 +747,7 @@ static int check_scanning_info(const struct ubi_device *ubi,
continue;
/*
* During scanning we found a volume which does not
* During attaching we found a volume which does not
* exist according to the information in the volume
* table. This must have happened due to an unclean
* reboot while the volume was being removed. Discard
......@@ -839,7 +837,7 @@ int ubi_read_volume_table(struct ubi_device *ubi, struct ubi_attach_info *ai)
* Make sure that the attaching information is consistent to the
* information stored in the volume table.
*/
err = check_scanning_info(ubi, ai);
err = check_attaching_info(ubi, ai);
if (err)
goto out_free;
......
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