| blob | 8cc6893fc56cd61a44015313e3cc5a907dff1115 |
1 /*
2 * JFFS -- Journaling Flash File System, Linux implementation.
3 *
4 * Copyright (C) 1999, 2000 Axis Communications, Inc.
5 *
6 * Created by Finn Hakansson <finn@axis.com>.
7 *
8 * This is free software; you can redistribute it and/or modify it
9 * under the terms of the GNU General Public License as published by
10 * the Free Software Foundation; either version 2 of the License, or
11 * (at your option) any later version.
12 *
13 * $Id: intrep.c,v 1.102 2001/09/23 23:28:36 dwmw2 Exp $
14 *
15 * Ported to Linux 2.3.x and MTD:
16 * Copyright (C) 2000 Alexander Larsson (alex@cendio.se), Cendio Systems AB
17 *
18 */
20 /* This file contains the code for the internal structure of the
21 Journaling Flash File System, JFFS. */
23 /*
24 * Todo list:
25 *
26 * memcpy_to_flash() and memcpy_from_flash() functions.
27 *
28 * Implementation of hard links.
29 *
30 * Organize the source code in a better way. Against the VFS we could
31 * have jffs_ext.c, and against the block device jffs_int.c.
32 * A better file-internal organization too.
33 *
34 * A better checksum algorithm.
35 *
36 * Consider endianness stuff. ntohl() etc.
37 *
38 * Are we handling the atime, mtime, ctime members of the inode right?
39 *
40 * Remove some duplicated code. Take a look at jffs_write_node() and
41 * jffs_rewrite_data() for instance.
42 *
43 * Implement more meaning of the nlink member in various data structures.
44 * nlink could be used in conjunction with hard links for instance.
45 *
46 * Better memory management. Allocate data structures in larger chunks
47 * if possible.
48 *
49 * If too much meta data is stored, a garbage collect should be issued.
50 * We have experienced problems with too much meta data with for instance
51 * log files.
52 *
53 * Improve the calls to jffs_ioctl(). We would like to retrieve more
54 * information to be able to debug (or to supervise) JFFS during run-time.
55 *
56 */
58 #include <linux/config.h>
59 #include <linux/types.h>
60 #include <linux/slab.h>
61 #include <linux/jffs.h>
62 #include <linux/fs.h>
63 #include <linux/stat.h>
64 #include <linux/pagemap.h>
65 #include <asm/semaphore.h>
66 #include <asm/byteorder.h>
67 #include <linux/smp_lock.h>
68 #include <linux/time.h>
69 #include <linux/ctype.h>
76 #if defined(JFFS_MEMORY_DEBUG) && JFFS_MEMORY_DEBUG
84 #endif
95 /* Is there enough space on the flash? */
97 {
104 }
111 }
112 }
113 }
115 #if CONFIG_JFFS_FS_VERBOSE > 0
116 static __u8
118 {
120 __u8 ret;
127 }
130 }
132 static void
134 {
144 }
148 }
151 }
152 }
154 /* Print empty space */
158 }
161 }
162 }
168 }
171 }
172 }
175 }
176 }
178 #endif
180 #define flash_safe_acquire(arg)
181 #define flash_safe_release(arg)
184 static int
187 {
197 }
199 }
202 static __u32
204 {
206 __u32 ret;
213 }
216 }
219 static int
222 {
232 }
234 }
237 static int
240 {
251 }
252 /* Not implemented writev. Repeatedly use write - on the not so
253 unreasonable assumption that the mtd driver doesn't care how
254 many write cycles we use. */
264 }
265 /* If res is non-zero, retlen_a is undefined, but we don't
266 care because in that case it's not going to be
267 returned anyway.
268 */
271 }
273 }
276 static int
279 {
283 /* fill up pattern */
288 /* write as many 64-byte chunks as we can */
294 }
296 /* and the rest */
302 }
305 static void
307 {
313 }
316 static int
319 {
322 wait_queue_head_t wait_q;
336 /* FIXME: Use TASK_INTERRUPTIBLE and deal with being interrupted */
349 }
357 }
359 /* This routine calculates checksums in JFFS. */
360 static __u32
362 {
367 }
370 }
373 static int
375 {
381 /* Allocate read buffer */
386 }
387 /* Loop until checksum done */
389 /* Get amount of data to read */
392 else
395 /* Perform flash read */
399 /* Compute checksum */
403 /* Update pointer and size */
406 }
408 /* Free read buffer */
411 /* Return result */
415 }
418 {
419 // down(&fmc->wlock);
420 }
423 {
424 // up(&fmc->wlock);
425 }
428 /* Create and initialize a new struct jffs_file. */
432 {
436 GFP_KERNEL))) {
439 }
440 no_jffs_file++;
449 }
452 /* Build a control block for the file system. */
455 {
465 }
473 }
479 }
484 fail_fminit:
486 fail_hash:
490 fail_control:
494 }
497 /* Clean up all data structures associated with the file system. */
498 void
500 {
506 }
513 }
515 /* Free all files and nodes. */
521 }
526 }
529 /* This function adds a virtual root node to the in-RAM representation.
530 Called by jffs_build_fs(). */
531 static int
533 {
541 GFP_KERNEL))) {
543 }
544 no_jffs_file++;
547 no_jffs_file--;
549 }
563 }
566 /* This is where the file system is built and initialized. */
567 int
569 {
577 }
582 /* scan_flash() wants us to try once more. A flipping
583 bits sector was detect in the middle of the scan flash.
584 Clean up old allocated memory before going in.
585 */
591 }
597 }
600 }
601 }
603 /* Add a virtual root node if no one exists. */
607 }
608 }
616 }
620 }
622 /* Remove deleted nodes. */
626 }
627 /* Remove redundant nodes. (We are not interested in the
628 return value in this case.) */
630 /* Try to build a tree from all the nodes. */
634 }
635 /* Compute the sizes of all files in the filesystem. Adjust if
636 necessary. */
640 }
649 jffs_build_fs_fail:
655 /*
656 This checks for sectors that were being erased in their previous
657 lifetimes and for some reason or the other (power fail etc.),
658 the erase cycles never completed.
659 As the flash array would have reverted back to read status,
660 these sectors are detected by the symptom of the "flipping bits",
661 i.e. bits being read back differently from the same location in
662 flash if read multiple times.
663 The only solution to this is to re-erase the entire
664 sector.
665 Unfortunately detecting "flipping bits" is not a simple exercise
666 as a bit may be read back at 1 or 0 depending on the alignment
667 of the stars in the universe.
668 The level of confidence is in direct proportion to the number of
669 scans done. By power fail testing I (Vipin) have been able to
670 proove that reading twice is not enough.
671 Maybe 4 times? Change NUM_REREADS to a higher number if you want
672 a (even) higher degree of confidence in your mount process.
673 A higher number would of course slow down your mount.
674 */
679 usually set to kernel page size */
688 __u32 offset;
693 /* Allocate read buffers */
702 }
704 CHECK_NEXT:
719 /* buffers MUST match, double word for word! */
722 ){
723 /* flipping bits detected, time to erase sector */
724 /* This will help us log some statistics etc. */
732 /* calculate start of present sector */
736 offset));
749 offset));
750 /* skip ahead to the next sector */
754 }
755 }
756 }
757 }
759 }
761 returnBack:
765 D2(printk("check_partly_erased_sector():Done checking all sectors till offset 0x%x for flipping bits.\n",
774 /* Scan the whole flash memory in order to find all nodes in the
775 file systems. */
776 static int
778 {
783 __u32 checksum;
784 __u8 tmp_accurate;
785 __u16 tmp_chksum;
786 __u32 deleted_file;
788 loff_t start;
789 loff_t test_start;
793 __u32 offset;
795 __u32 free_chunk_size1;
796 __u32 free_chunk_size2;
801 free blocks found. This is NOT allowed
802 by the current jffs design.
803 */
805 of how much free space was rejected and
806 marked dirty
807 */
814 /*
815 check and make sure that any sector does not suffer
816 from the "partly erased, bit flipping syndrome" (TM Vipin :)
817 If so, offending sectors will be erased.
818 */
823 }
825 /* Allocate read buffer */
830 }
832 /* Start the scan. */
836 /* Remember the position from where we started this scan. */
841 /* We have found 0xffffffff at this position. We have to
842 scan the rest of the flash till the end or till
843 something else than 0xffffffff is found.
844 Keep going till we do not find JFFS_EMPTY_BITMASK
845 anymore */
861 JFFS_EMPTY_BITMASK)
863 }
866 else
868 }
873 /* If some free space ends in the middle of a sector,
874 treat it as dirty rather than clean.
875 This is to handle the case where one thread
876 allocated space for a node, but didn't get to
877 actually _write_ it before power was lost, leaving
878 a gap in the log. Shifting all node writes into
879 a single kernel thread will fix the original problem.
880 */
882 /* If there was free space in previous
883 sectors, don't mark that dirty too -
884 only from the beginning of this sector
885 (or from start)
886 */
892 /* free space started in the previous sector! */
897 /*
898 Count it in if we are still under NUMFREEALLOWED *and* it is
899 at least 1 erase sector in length. This will keep us from
900 picking any little ole' space as "free".
901 */
910 /* below, space from "start" to "pos" will be marked dirty. */
913 /* Being in here means that we have found at least an entire
914 erase sector size of free space ending on a sector boundary.
915 Keep track of free spaces accepted.
916 */
917 num_free_space++;
919 num_free_spc_not_accp++;
925 }
927 }
935 /* "Flipping bits" detected. This means that our scan for them
936 did not catch this offset. See check_partly_erased_sectors() for
937 more info.
938 */
945 /* calculate start of present sector */
949 offset));
961 }
966 }
968 /* Being in here means that we have found free space that ends on an erase sector
969 boundary.
970 Count it in if we are still under NUMFREEALLOWED *and* it is at least 1 erase
971 sector in length. This will keep us from picking any little ole' space as "free".
972 */
975 /* We really don't do anything to mark space as free, except *not*
976 mark it dirty and just advance the "pos" location pointer.
977 It will automatically be picked up as free space.
978 */
979 num_free_space++;
983 num_free_spc_not_accp++;
989 /* Mark this space as dirty. We already have our free space. */
994 }
996 }
1001 }
1005 /* We have found 0x00000000 at this position. Scan as far
1006 as possible to find out how much is dirty. */
1019 /* We have probably found a new raw inode. */
1023 bad_inode:
1024 /* We're f*cked. This is not solved yet. We have
1025 to scan for the magic pattern. */
1027 "bad inode: "
1036 /* handle these in the main switch() loop */
1041 }
1042 }
1044 cont_scan:
1045 /* First, mark as dirty the region
1046 which really does contain crap. */
1049 NULL);
1054 /* We have found the beginning of an inode. Create a
1055 node for it unless there already is one available. */
1058 /* Free read buffer */
1061 /* Release the flash device */
1065 }
1067 }
1069 /* Read the next raw inode. */
1074 /* When we compute the checksum for the inode, we never
1075 count the 'accurate' or the 'checksum' fields. */
1091 "checksum = %u, "
1097 /* Reuse this unused struct jffs_node. */
1099 }
1101 /* Check the raw inode read so far. Start with the
1102 maximum length of the filename. */
1107 }
1115 }
1117 /* The node's data segment should not exceed a
1118 certain length. */
1124 }
1128 /* This shouldn't be necessary because a node that
1129 violates the flash boundaries shouldn't be written
1130 in the first place. */
1133 }
1135 /* Read the name. */
1146 "checksum = %u, "
1151 /* Reuse this unused struct jffs_node. */
1153 }
1156 }
1157 }
1159 /* Read the data, if it exists, in order to be sure it
1160 matches the checksum. */
1164 }
1169 /* Reuse this unused struct jffs_node. */
1171 }
1177 "checksum = %u, "
1182 /* Reuse this unused struct jffs_node. */
1184 }
1185 }
1187 check_node:
1189 /* Remember the highest inode number in the whole file
1190 system. This information will be used when assigning
1191 new files new inode numbers. */
1194 }
1201 /* Compute the offset to the actual data in the
1202 on-flash node. */
1203 node->fm_offset
1209 node);
1215 /* Free read buffer */
1218 /* Release the flash device */
1222 }
1228 }
1233 GFP_KERNEL);
1239 /* Release the flash device */
1242 /* Free read buffer */
1246 }
1251 }
1254 }
1260 /* Reuse this unused struct jffs_node. */
1261 }
1262 }
1267 }
1270 /* Free read buffer */
1276 }
1278 /* Return happy */
1282 /* This is to trap the "free size accounting screwed error. */
1294 Mounting this screwed up f/s will screw us up anyway.
1295 */
1296 }
1302 /* Insert any kind of node into the file system. Take care of data
1303 insertions and deletions. Also remove redundant information. The
1304 memory allocated for the `name' is regarded as "given away" in the
1305 caller's perspective. */
1306 int
1310 {
1319 /* If there doesn't exist an associated jffs_file, then
1320 create, initialize and insert one into the file system. */
1324 }
1327 }
1335 /* Now insert the node at the correct position into the file's
1336 version list. */
1338 /* This is the first node. */
1351 }
1354 /* Insert at the end of the list. I.e. this node is the
1355 newest one so far. */
1369 }
1371 /* Insert at the bottom of the list. */
1378 }
1379 }
1383 /* Search for the insertion position starting from
1384 the tail (newest node). */
1393 }
1395 }
1398 }
1399 }
1400 }
1402 /* Deletion is irreversible. If any 'deleted' node is ever
1403 written, the file is deleted */
1407 /* Perhaps update the name. */
1412 }
1414 GFP_KERNEL))) {
1416 }
1423 }
1430 }
1431 /* Once upon a time, we would call jffs_possibly_delete_file()
1432 here. That causes an oops if someone's still got the file
1433 open, so now we only do it in jffs_delete_inode()
1434 -- dwmw2
1435 */
1438 }
1445 }
1451 /* Unlink a jffs_node from the version list it is in. */
1455 {
1460 }
1465 }
1466 }
1469 /* Unlink a jffs_node from the range list it is in. */
1472 {
1475 }
1478 }
1481 }
1484 }
1485 }
1488 /* Function used by jffs_remove_redundant_nodes() below. This function
1489 classifies what kind of information a node adds to a file. */
1492 {
1497 }
1500 }
1502 }
1505 /* Remove redundant nodes from a file. Mark the on-flash memory
1506 as dirty. */
1507 static int
1509 {
1513 __u8 newest_type;
1514 __u8 mod_type;
1519 }
1521 /* What does the `newest_node' modify? */
1527 newest_type));
1529 /* Traverse the file's nodes and determine which of them that are
1530 superfluous. Yeah, this might look very complex at first
1531 glance but it is actually very simple. */
1537 && (mod_type
1541 /* Yes, this node is redundant. Remove it. */
1543 "Removing node: ino: %u, version: %u, "
1545 mod_type));
1550 }
1553 }
1554 }
1557 }
1560 /* Insert a file into the hash table. */
1561 static int
1563 {
1570 }
1573 /* Insert a file into the file system tree. */
1574 int
1576 {
1589 }
1595 }
1596 }
1601 }
1605 }
1608 /* Remove a file from the hash table. */
1609 static int
1611 {
1617 }
1620 /* Just remove the file from the parent's children. Don't free
1621 any memory. */
1622 int
1624 {
1630 }
1634 }
1637 }
1639 }
1642 /* Find a file with its inode number. */
1645 {
1659 );
1661 }
1664 );
1666 }
1669 /* Find a file in a directory. We are comparing the names. */
1672 {
1682 }
1683 }
1687 }
1693 }
1698 }
1699 });
1702 }
1705 /* Write a raw inode that takes up a certain amount of space in the flash
1706 memory. At the end of the flash device, there is often space that is
1707 impossible to use. At these times we want to mark this space as not
1708 used. In the cases when the amount of space is greater or equal than
1709 a struct jffs_raw_inode, we write a "dummy node" that takes up this
1710 space. The space after the raw inode, if it exists, is left as it is.
1711 Since this space after the raw inode contains JFFS_EMPTY_BITMASK bytes,
1712 we can compute the checksum of it; we don't have to manipulate it any
1713 further.
1715 If the space left on the device is less than the size of a struct
1716 jffs_raw_inode, this space is filled with JFFS_DIRTY_BITMASK bytes.
1717 No raw inode is written this time. */
1718 static int
1720 {
1735 raw_inode.chksum
1746 }
1747 }
1752 }
1756 }
1759 /* Write a raw inode, possibly its name and possibly some data. */
1760 int
1766 {
1772 __u32 pos;
1783 /* If this node isn't something that will eventually let
1784 GC free even more space, then don't allow it unless
1785 there's at least max_chunk_size space still available
1786 */
1791 /* Fire the retrorockets and shoot the fruiton torpedoes, sir! */
1796 });
1801 });
1806 total_size));
1810 retry:
1815 /* Deadlocks suck. */
1821 }
1823 /* First try to allocate some flash memory. */
1827 /* Just out of space. GC and try again */
1831 total_size));
1833 }
1840 }
1843 }
1851 }
1854 /* The jffs_fm struct that we got is not good enough.
1855 Make that space dirty and try again */
1863 }
1865 }
1871 });
1875 /* Increment the version number here. We can't let the caller
1876 set it beforehand, because we might have had to do GC on a node
1877 of this file - and we'd end up reusing version numbers.
1878 */
1881 D1(printk (KERN_NOTICE "jffs_write_node(): setting version of %s to %d\n", f->name, raw_inode->version));
1883 /* if the file was deleted, set the deleted bit in the raw inode */
1886 }
1888 /* Compute the checksum for the data and name chunks. */
1892 /* The checksum is calculated without the chksum and accurate
1893 fields so set them to zero first. */
1904 /* The actual raw JFFS node */
1909 /* Get name and size if there is one */
1913 iovec_cnt++;
1917 /* Add some extra padding if necessary */
1921 iovec_cnt++;
1922 }
1923 }
1925 /* Get data and size if there is any */
1929 iovec_cnt++;
1930 /* No need to pad this because we're not actually putting
1931 anything after it.
1932 */
1933 }
1942 }
1952 /* Read data from the node and write it to the buffer. 'node_offset'
1953 is how much we have read from this particular node before and which
1954 shouldn't be read again. 'max_size' is how much space there is in
1955 the buffer. */
1956 static int
1959 {
1963 __u32 r;
1977 }
1980 /* Read data from the file's nodes. Write the data to the buffer
1981 'buf'. 'read_offset' tells how much data we should skip. */
1982 int
1984 __u32 size)
1985 {
1998 }
2000 /* First find the node to read data from. */
2007 }
2010 }
2011 }
2013 /* "Cats are living proof that not everything in nature
2014 has to be useful."
2015 - Garrison Keilor ('97) */
2017 /* Fill the buffer. */
2021 /* This node does not refer to real data. */
2025 }
2027 node_offset,
2030 }
2034 }
2037 }
2040 /* Used for traversing all nodes in the hash table. */
2041 int
2043 {
2051 /* We need a reference to the next file in the
2052 list because `func' might remove the current
2053 file `f'. */
2059 }
2060 }
2063 }
2066 /* Free all nodes associated with a file. */
2067 static int
2069 {
2081 }
2083 }
2086 /* Free a file and its name. */
2087 static int
2089 {
2096 }
2098 no_jffs_file--;
2100 }
2102 static long
2104 {
2106 }
2108 /* See if a file is deleted. If so, mark that file's nodes as obsolete. */
2109 int
2111 {
2120 });
2123 /* First try to remove all older versions. Commence with
2124 the oldest node. */
2128 }
2131 }
2132 }
2133 /* Unlink the file from the filesystem. */
2136 }
2140 }
2142 }
2145 /* Used in conjunction with jffs_foreach_file() to count the number
2146 of files in the file system. */
2147 int
2149 {
2151 }
2154 /* Build up a file's range list from scratch by going through the
2155 version list. */
2156 static int
2158 {
2166 }
2168 }
2171 /* Remove an amount of data from a file. If this amount of data is
2172 zero, that could mean that a node should be split in two parts.
2173 We remove or change the appropriate nodes in the lists.
2175 Starting offset of area to be removed is node->data_offset,
2176 and the length of the area is in node->removed_size. */
2177 static int
2179 {
2191 /* A simple append; nothing to remove or no node to split. */
2193 }
2195 /* Find the node where we should begin the removal. */
2199 }
2200 }
2202 /* If there's no data in the file there's no data to
2203 remove either. */
2205 }
2208 /* XXX: Not implemented yet. */
2211 }
2213 /* See if the node has to be split into two parts. */
2215 /* Do the split. */
2223 }
2238 }
2241 }
2247 }
2250 }
2251 /* A very interesting can of worms. */
2259 }
2262 }
2264 /* No. No need to split the node. Just remove
2265 the end of the node. */
2271 }
2272 }
2274 /* Remove as many nodes as necessary. */
2286 }
2291 }
2298 }
2299 }
2301 /* Adjust the following nodes' information about offsets etc. */
2305 }
2308 /* It's possible that the removed_size is in fact
2309 * greater than the amount of data we actually thought
2310 * were present in the first place - some of the nodes
2311 * which this node originally obsoleted may already have
2312 * been deleted from the flash by subsequent garbage
2313 * collection.
2314 *
2315 * If this is the case, don't let f->size go negative.
2316 * Bad things would happen :)
2317 */
2321 }
2327 /* Insert some data into a file. Prior to the call to this function,
2328 jffs_delete_data should be called. */
2329 static int
2331 {
2336 /* Find the position where we should insert data. */
2337 retry:
2339 /* A simple append. This is the most common operation. */
2344 }
2349 }
2350 }
2352 /* Trying to insert data into the middle of the file. This
2353 means no problem because jffs_delete_data() has already
2354 prepared the range list for us. */
2357 /* Find the correct place for the insertion and then insert
2358 the node. */
2366 }
2369 }
2373 }
2377 "Couldn't find a place to insert "
2380 });
2381 }
2383 /* Adjust later nodes' offsets etc. */
2388 }
2390 }
2392 /* Okay. This is tricky. This means that we want to insert
2393 data at a place that is beyond the limits of the file as
2394 it is constructed right now. This is actually a common
2395 event that for instance could occur during the mounting
2396 of the file system if a large file have been truncated,
2397 rewritten and then only partially garbage collected. */
2401 /* We need a place holder for the data that is missing in
2402 front of this insertion. This "virtual node" will not
2403 be associated with any space on the flash device. */
2407 }
2423 /* Are there any data at all in the file yet? */
2425 virtual_node->data_offset
2428 virtual_node->data_size
2432 }
2438 }
2443 /* Insert this virtual node in the version list as well. */
2449 virtual_node->version_prev
2451 }
2454 }
2457 }
2458 }
2462 /* Make a new try to insert the node. */
2464 }
2468 }
2471 /* A new node (with data) has been added to the file and now the range
2472 list has to be modified. */
2473 static int
2475 {
2483 /* data_offset == X */
2484 /* data_size == 0 */
2485 /* remove_size == 0 */
2486 }
2488 /* data_offset == X */
2489 /* data_size == 0 */
2490 /* remove_size != 0 */
2493 }
2494 }
2495 }
2497 /* data_offset == X */
2498 /* data_size != 0 */
2499 /* remove_size == Y */
2502 }
2505 }
2506 }
2508 }
2510 /* Print the contents of a node. */
2511 void
2513 {
2529 }
2532 /* Print the contents of a raw inode. */
2533 void
2535 {
2565 }
2568 /* Print the contents of a file. */
2569 #if 0
2570 int
2572 {
2590 });
2608 }
2611 void
2613 {
2625 }
2626 }
2627 }
2630 void
2632 {
2639 }
2644 }
2656 }
2657 }
2660 }
2663 #if defined(JFFS_MEMORY_DEBUG) && JFFS_MEMORY_DEBUG
2664 void
2666 {
2679 }
2680 #endif
2683 /* Rewrite `size' bytes, and begin at `node'. */
2684 static int
2686 {
2692 __u32 pos;
2693 __u32 pos_dchksum;
2694 __u32 total_name_size;
2695 __u32 total_data_size;
2696 __u32 total_size;
2702 /* Create and initialize the new node. */
2707 }
2718 retry:
2728 }
2730 /* The jffs_fm struct that we got is not big enough. */
2731 /* This should never happen, because we deal with this case
2732 in jffs_garbage_collect_next().*/
2733 printk(KERN_WARNING "jffs_rewrite_data(): Allocated node is too small (%d bytes of %d)\n", fm->size, total_size);
2739 }
2745 }
2748 /* Initialize the raw inode. */
2791 }
2794 /* Write the name to the flash memory. */
2808 }
2811 }
2813 /* Write the data. */
2822 }
2832 "jffs_read_data() "
2835 }
2842 "Write error during rewrite. "
2845 }
2850 }
2853 }
2860 /* Add the checksum. */
2872 }
2874 /* Now make the file system aware of the newly written node. */
2883 /* jffs_garbage_collect_next implements one step in the garbage collect
2884 process and is often called multiple times at each occasion of a
2885 garbage collect. */
2887 static int
2889 {
2894 __u32 size;
2895 __u32 data_size;
2896 __u32 total_name_size;
2897 __u32 extra_available;
2898 __u32 space_needed;
2902 /* Get the oldest node in the flash. */
2911 });
2913 /* Find its corresponding file too. */
2918 "No file to garbage collect! "
2920 /* FIXME: Free the offending node and recover. */
2923 }
2925 /* We always write out the name. Theoretically, we don't need
2926 to, but for now it's easier - because otherwise we'd have
2927 to keep track of how many times the current name exists on
2928 the flash and make sure it never reaches zero.
2930 The current approach means that would be possible to cause
2931 the GC to end up eating its tail by writing lots of nodes
2932 with no name for it to garbage-collect. Hence the change in
2933 inode.c to write names with _every_ node.
2935 It sucks, but it _should_ work.
2936 */
2944 /* Compute how many data it's possible to rewrite at the moment. */
2947 /* And from that, the total size of the chunk we want to write */
2951 /* If that's more than max_chunk_size, reduce it accordingly */
2956 }
2958 /* If we're asking to take up more space than free_chunk_size1
2959 but we _could_ fit in it, shrink accordingly.
2960 */
2965 /* The space left is too small to be of any
2966 use really. */
2973 "jffs_garbage_collect_next: "
2974 "Failed to allocate `dirty' "
2978 }
2983 }
2991 }
2994 /* Calculate the amount of space needed to hold the nodes
2995 which are remaining in the tail */
2998 /* From that, calculate how much 'extra' space we can use to
2999 increase the size of the node we're writing from the size
3000 of the node we're obsoleting
3001 */
3003 /* If we've gone below min_free_size for some reason,
3004 don't fuck up. This is why we have
3005 min_free_size > sector_size. Whinge about it though,
3006 just so I can convince myself my maths is right.
3007 */
3014 }
3016 /* Check that we don't use up any more 'extra' space than
3017 what's available */
3031 };
3046 }
3048 jffs_garbage_collect_next_end:
3054 /* If an obsolete node is partly going to be erased due to garbage
3055 collection, the part that isn't going to be erased must be filled
3056 with zeroes so that the scan of the flash will work smoothly next
3057 time. (The data in the file could for instance be a JFFS image
3058 which could cause enormous confusion during a scan of the flash
3059 device if we didn't do this.)
3060 There are two phases in this procedure: First, the clearing of
3061 the name and data parts of the node. Second, possibly also clearing
3062 a part of the raw inode as well. If the box is power cycled during
3063 the first phase, only the checksum of this node-to-be-cleared-at-
3064 the-end will be wrong. If the box is power cycled during, or after,
3065 the clearing of the raw inode, the information like the length of
3066 the name and data parts are zeroed. The next time the box is
3067 powered up, the scanning algorithm manages this faulty data too
3068 because:
3070 - The checksum is invalid and thus the raw inode must be discarded
3071 in any case.
3072 - If the lengths of the data part or the name part are zeroed, the
3073 scanning just continues after the raw inode. But after the inode
3074 the scanning procedure just finds zeroes which is the same as
3075 dirt.
3077 So, in the end, this could never fail. :-) Even if it does fail,
3078 the scanning algorithm should manage that too. */
3080 static int
3082 {
3085 __u32 zero_offset;
3086 __u32 zero_size;
3087 __u32 zero_offset_data;
3088 __u32 zero_size_data;
3094 }
3096 /* Where and how much shall we clear? */
3100 /* Do we have to clear the raw_inode explicitly? */
3104 }
3106 /* First, clear the name and data fields. */
3113 /* Should we clear a part of the raw inode? */
3115 /* I guess it is ok to clear the raw inode in this order. */
3118 cutting_raw_inode);
3120 }
3125 /* Try to erase as much as possible of the dirt in the flash memory. */
3126 static long
3128 {
3132 __u32 offset;
3142 }
3147 }
3153 }
3157 /* Now, let's try to do the erase. */
3163 /* XXX: Here we should allocate this area as dirty
3164 with jffs_fmalloced or something similar. Now
3165 we just report the error. */
3167 }
3169 #if 0
3170 /* Check if the erased sectors really got erased. */
3171 {
3172 __u32 pos;
3173 __u32 end;
3190 }
3191 }
3197 }
3199 /* XXX: Here we should allocate the memory
3200 with jffs_fmalloced() in order to prevent
3201 JFFS from using this area accidentally. */
3203 }
3204 }
3205 #endif
3207 /* Update the flash memory data structures. */
3211 }
3214 /* There are different criteria that should trigger a garbage collect:
3216 1. There is too much dirt in the memory.
3217 2. The free space is becoming small.
3218 3. There are many versions of a node.
3220 The garbage collect should always be done in a manner that guarantees
3221 that future garbage collects cannot be locked. E.g. Rewritten chunks
3222 should not be too large (span more than one sector in the flash memory
3223 for exemple). Of course there is a limit on how intelligent this garbage
3224 collection can be. */
3227 static int
3229 {
3234 D2(printk("***jffs_garbage_collect_now(): fmc->dirty_size = %u, fmc->free_size = 0x%x\n, fcs1=0x%x, fcs2=0x%x",
3238 // down(&fmc->gclock);
3240 /* If it is possible to garbage collect, do so. */
3252 }
3257 /* Argh */
3261 }
3264 /* Actually, we _may_ have been able to free some,
3265 * if there are many overlapping nodes which aren't
3266 * actually marked dirty because they still have
3267 * some valid data in each.
3268 */
3271 }
3273 /* Let's dare to make a garbage collect. */
3276 "has gone seriously wrong "
3279 }
3283 }
3285 gc_end:
3286 // up(&fmc->gclock);
3292 });
3301 /* Determine if it is reasonable to start garbage collection.
3302 We start a gc pass if either:
3303 - The number of free bytes < MIN_FREE_BYTES && at least one
3304 block is dirty, OR
3305 - The number of dirty bytes > MAX_DIRTY_BYTES
3306 */
3308 {
3312 /* If there's not enough dirty space to free a block, there's no point. */
3316 }
3317 #if 1
3318 /* If there is too much RAM used by the various structures, GC */
3319 if (jffs_get_node_inuse() > (c->fmc->used_size/c->fmc->max_chunk_size * 5 + jffs_get_file_count() * 2 + 50)) {
3320 /* FIXME: Provide proof that this test can be satisfied. We
3321 don't want a filesystem doing endless GC just because this
3322 condition cannot ever be false.
3323 */
3326 }
3327 #endif
3328 /* If there are fewer free bytes than the threshold, GC */
3332 }
3333 /* If there are more dirty bytes than the threshold, GC */
3337 }
3338 /* FIXME: What about the "There are many versions of a node" condition? */
3341 }
3345 {
3346 /* NOTE: We rely on the fact that we have the BKL here.
3347 * Otherwise, the gc_task could go away between the check
3348 * and the wake_up_process()
3349 */
3352 }
3355 /* Kernel threads take (void *) as arguments. Thus we pass
3356 the jffs_control data as a (void *) and then cast it. */
3357 int
3359 {
3373 siginitsetinv (¤t->blocked, sigmask(SIGHUP) | sigmask(SIGKILL) | sigmask(SIGSTOP) | sigmask(SIGCONT));
3381 /* See if we need to start gc. If we don't, go to sleep.
3383 Current implementation is a BAD THING(tm). If we try
3384 to unmount the FS, the unmount operation will sleep waiting
3385 for this thread to exit. We need to arrange to send it a
3386 sig before the umount process sleeps.
3387 */
3393 on immediately - we're a low priority
3394 background task. */
3396 /* Put_super will send a SIGKILL and then wait on the sem.
3397 */
3399 siginfo_t info;
3417 }
3418 }
3433 }
3439 /* Argh. Might as well commit suicide. */
3442 // panic()
3444 }
3446 /* Let's dare to make a garbage collect. */
3449 "has gone seriously wrong "
3451 }
3453 gc_end: