Re: JFFS2 bug with overwriting files bigger than 50% of the file system?
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Hi, > > > > Hi, > > > > I stumbled upon a problem with JFFS2. > > > > When overwriting a relatively large file (580 kB in a 896 kB flash > > region), > > the file system breaks. > > > What is your block size, or more precisely, the size of the erase blocks? > Often it is 128kB. > JFFS2 needs some spare blocks for garbage collection. I don't remember > if the default is 3 or 5. > 3 means 384kB, so only 512kB is available. And if you still force to use > it, it _will_ give problems. > > The block size is 64 kB, and there are 14 blocks in total. The file takes up 6 blocks (with compression), so 8 blocks are free. These are the settings for the amount of reserved blocks: resv_blocks_write = 3, resv_blocks_deletion = 2, resv_blocks_gctrigger = 4, resv_blocks_gcbad = 0, resv_blocks_gcmerge = 3. If I understood you correctly, deleting and saving the file again should work fine by these numbers. I tried increasing the FS size by 8 blocks, but the problem still persists. After that I tried to run the GC from application code between deleting and re-writing the file, but saw that this isn't possible without some ugly hacks, so I decided to reply to this ML first before getting down to that (depending on the answer). Anyhow, the GC should be run before re-writing the file anyways, if I under- stood things right, so triggering it manually would probably not help either. > > > > Plenty of errors like these ensue when trying to read the new, > > overwritten file > > after a reboot: > > > > BUG() at ~/ecos-2.0.40/packages/fs/jffs2/v2_0_40/src/readinode.c 381 > > <5>JFFS2 notice: read_unknown: node header CRC failed at %#08x. But > > it must hav > > e been OK earlier. > > <4>Node totlen on flash (0xffffffff) != totlen from node ref > (0x00000044) > > <4>JFFS2 warning: jffs2_do_read_inode_internal: no data nodes found > > for ino #3 > > <5>JFFS2 notice: jffs2_do_read_inode_internal: but it has children so > > we fake s > > ome modes for it > > <4>JFFS2 warning: jffs2_do_read_inode_internal: no data nodes found > > for ino #3 > > <5>JFFS2 notice: jffs2_do_read_inode_internal: but it has children so > > we fake s > > ome modes for it > > > > It does not matter if the new file is identical with the old file. > > Unlinking and then writing the file again causes the same result. > > > FYI: JFFS2 is a log based file system, better read about it if you don't > know that (I can give some pointers). It means that you cannot overwrite > a file: instead, the file is marked (in the file system meta data or > table of contents) for removal, and the new version of the file is > appended in the file system. If the file system is full, garbage > collection (GC) starts to recover blocks, using those spare blocks. > And GC can take some time (and then all file system accesses are frozen, > e.g. the TFTP server), resulting e.g. in a TFTP timeout in the client. > And if GC can free a block, and then the client resends a TFTP packet, > the same data portion can be present in double... I have seen several > file system problems when stress testing it.. > Also mark that on a flash you cannot delete bytes, only per erase block. Thanks, I had a vague concept of journalling or log-based filesystems in mind, but never looked at the details. > > If this is more or less a known problem, how likely is it that small > > files (say, > > being smaller than 50% of the file system's storage space) cause this > > behaviour > > as well? > > > > I noticed that the current version in the eCos source tree lags a bit > > behind the > > code in the Linux kernel. Maybe this issue has been fixed there > > already and only > > requires a port of the current code to eCos. > > > indeed, already for a long time a volunteer is needed to update the ecos > jffs2 code. > > Regards, > Jürgen > > > > > > I'd be grateful for any ideas about this problem, even if it is just > > pointing me > > to the linux-mtd mailing list. > > > > Thanks, > > > > Gunnar Ruthenberg. > > > Any more suggestions? Thanks, Gunnar Ruthenberg. -- NEU: FreePhone - 0ct/min Handyspartarif mit Geld-zurück-Garantie! Jetzt informieren: http://www.gmx.net/de/go/freephone -- Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss