So let me talk about what were some of the last couple of things that I did before I folded the undo-mgr into the tree, since it might be helpful for other people who are into hacking e2fsprogs. 1) I used "make gcc-wall" (or if you only want to scan for changes in e2undo.c, you can use the command; "rm e2undo.o; make gcc-wall-new") to scan for warnings; this turned up some interesting bugs. Please, make sure your code is gcc-Wall clean. In some cases the pre-existing code isn't, due to folks being lazy or gcc -Wall becoming more strict. But your patch shouldn't make things worse. 2) Compiling with the --enable-testio-debug configure option, I used the command "export TEST_IO_FLAGS=0xffff" to set the environment variable to see the I/O pattern of various programs like "mke2fs" with the config option defaults.force_undo=1 set. This is how I discovered that we were using a pathetically small tdb_data_size, and changing it to 32768 cut the mke2fs time in half. Some more investigation showed that part of the problem was we were initializing the journal one block at a time, causing significant overhead. When I changed lib/ext2fs/mkjournal.c to zero out the journal 8 blocks at a time, aligned on 8 block boundary to make life easier for the undo manager, and made a similar change when zero'ing out the inode table so it would also be issue writes aligned on 8 block boundaries, I was able to cut the mke2fs time in half again. So for everyone who had been complaining about mke2fs taking too much time with the undo option --- we do have tools in e2fsprogs that can be used to help profile its operation and speed things up. You can also use seekwatcher/blktrace, of course, but there are also other userspace tools that can be used. 3) I also changed the name of the files created by the undo manager to include an .e2undo suffix. This makes it much more likely that system administrators will understand what the file is and what it is used for. If people are looking for things to do with the undo manager --- it would be good to wire up e2fsck and resize2fs to use it --- and at this point, it would probably make sense to factor out common code for setting up the undo manager into undo_mgr.c itself (although remember the rules, nothing in libext2fs should try to write to stdout; library routines must return error codes, and leave the printing of any status or error messages to the application). - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
