Messages in this thread | | | Subject | Re: [PATCH 5/9] writeback: introduce the pageout work | From | Artem Bityutskiy <> | Date | Mon, 12 Mar 2012 14:36:14 +0200 |
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On Fri, 2012-03-09 at 22:11 +0100, Jan Kara wrote: > On Fri 09-03-12 18:10:51, Artem Bityutskiy wrote: > > On Fri, 2012-03-09 at 10:51 +0100, Jan Kara wrote: > > > > However I cannot find any ubifs functions to form the above loop, so > > > > ubifs should be safe for now. > > > Yeah, me neither but I also failed to find a place where > > > ubifs_evict_inode() truncates inode space when deleting the inode... Artem? > > > > We do call 'truncate_inode_pages()': > > > > static void ubifs_evict_inode(struct inode *inode) > > { > > ... > > > > truncate_inode_pages(&inode->i_data, 0); > > > > ... > > } > Well, but that just removes pages from page cache. You should somewhere > also free allocated blocks and free the inode... And I'm sure you do, > otherwise you would pretty quickly notice that file deletion does not work > :) Just I could not find which function does it.
ubifs_evict_inode() -> ubifs_jnl_delete_inode() -> ubifs_tnc_remove_ino()
Basically, deletion in UBIFS is about writing a so-called "deletion inode" to the journal and then removing all the data nodes of the truncated inode from the TNC (in-memory cache of the FS index, which is just a huge B-tree, like in reiser4 which inspired me long time ago, and like in btrfs).
The second part of the overall deletion job will be when we commit - the updated version of the FS index will be written to the flash media.
If we get a power cut before the commit, the journal reply will see the deletion inode and will clean-up the index. The deletion inode is never erased before the commit.
Basically, this design is dictated by the fact that we do not have a cheap way of doing in-place updates.
This is a short version of the story. Here are some docs as well: http://www.linux-mtd.infradead.org/doc/ubifs.html#L_documentation
-- Best Regards, Artem Bityutskiy
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