lwn.git/drivers/block/rd.c, branch v2.6.32.41

rewrite rd

2008-02-08T17:22:30+00:00

This is a rewrite of the ramdisk block device driver. The old one is really difficult because it effectively implements a block device which serves data out of its own buffer cache. It relies on the dirty bit being set, to pin its backing store in cache, however there are non trivial paths which can clear the dirty bit (eg. try_to_free_buffers()), which had recently lead to data corruption. And in general it is completely wrong for a block device driver to do this. The new one is more like a regular block device driver. It has no idea about vm/vfs stuff. It's backing store is similar to the buffer cache (a simple radix-tree of pages), but it doesn't know anything about page cache (the pages in the radix tree are not pagecache pages). There is one slight downside -- direct block device access and filesystem metadata access goes through an extra copy and gets stored in RAM twice. However, this downside is only slight, because the real buffercache of the device is now reclaimable (because we're not playing crazy games with it), so under memory intensive situations, footprint should effectively be the same -- maybe even a slight advantage to the new driver because it can also reclaim buffer heads. The fact that it now goes through all the regular vm/fs paths makes it much more useful for testing, too. text data bss dec hex filename 2837 849 384 4070 fe6 drivers/block/rd.o 3528 371 12 3911 f47 drivers/block/brd.o Text is larger, but data and bss are smaller, making total size smaller. A few other nice things about it: - Similar structure and layout to the new loop device handlinag. - Dynamic ramdisk creation. - Runtime flexible buffer head size (because it is no longer part of the ramdisk code). - Boot / load time flexible ramdisk size, which could easily be extended to a per-ramdisk runtime changeable size (eg. with an ioctl). - Can use highmem for the backing store. [akpm@linux-foundation.org: fix build] [byron.bbradley@gmail.com: make rd_size non-static] Signed-off-by: Nick Piggin Signed-off-by: Byron Bradley Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

rd: use is_power_of_2() in drivers/block/rd.c.

2008-02-06T18:41:03+00:00

Signed-off-by: Robert P. J. Day Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

rd: fix data corruption on memory pressure

2007-11-15T02:45:42+00:00

We have seen ramdisk based install systems, where some pages of mapped libraries and programs were suddendly zeroed under memory pressure. This should not happen, as the ramdisk avoids freeing its pages by keeping them dirty all the time. It turns out that there is a case, where the VM makes a ramdisk page clean, without telling the ramdisk driver. On memory pressure shrink_zone runs and it starts to run shrink_active_list. There is a check for buffer_heads_over_limit, and if true, pagevec_strip is called. pagevec_strip calls try_to_release_page. If the mapping has no releasepage callback, try_to_free_buffers is called. try_to_free_buffers has now a special logic for some file systems to make a dirty page clean, if all buffers are clean. Thats what happened in our test case. The simplest solution is to provide a noop-releasepage callback for the ramdisk driver. This avoids try_to_free_buffers for ramdisk pages. Signed-off-by: Christian Borntraeger Acked-by: Nick Piggin Cc: "Eric W. Biederman" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Fix misspellings of "system", "controller", "interrupt" and "necessary".

2007-10-19T21:10:43+00:00

Fix the various misspellings of "system", controller", "interrupt" and "[un]necessary". Signed-off-by: Robert P. J. Day Signed-off-by: Adrian Bunk

Remove final traces of long-deprecated "ramdisk" kernel parm

2007-10-17T15:42:56+00:00

Since the "ramdisk" kernel parameter has been officially deprecated since at least 2.6.18, might as well finally get rid of it. Signed-off-by: Robert P. J. Day Acked-by: Geert Uytterhoeven Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: bdi init hooks

2007-10-17T15:42:45+00:00

provide BDI constructor/destructor hooks [akpm@linux-foundation.org: compile fix] Signed-off-by: Peter Zijlstra Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Drop 'size' argument from bio_endio and bi_end_io

2007-10-10T07:25:57+00:00

As bi_end_io is only called once when the reqeust is complete, the 'size' argument is now redundant. Remove it. Now there is no need for bio_endio to subtract the size completed from bi_size. So don't do that either. While we are at it, change bi_end_io to return void. Signed-off-by: Neil Brown Signed-off-by: Jens Axboe

[BLOCK] Get rid of request_queue_t typedef

2007-07-24T07:28:11+00:00

Some of the code has been gradually transitioned to using the proper struct request_queue, but there's lots left. So do a full sweet of the kernel and get rid of this typedef and replace its uses with the proper type. Signed-off-by: Jens Axboe

Fix occurrences of "the the "

2007-05-09T06:57:56+00:00

Signed-off-by: Michael Opdenacker Signed-off-by: Adrian Bunk

mm: remove destroy_dirty_buffers from invalidate_bdev()

2007-05-07T19:12:55+00:00

Remove the destroy_dirty_buffers argument from invalidate_bdev(), it hasn't been used in 6 years (so akpm says). find * -name \*.[ch] | xargs grep -l invalidate_bdev | while read file; do quilt add $file; sed -ie 's/invalidate_bdev($[^,]*$,[^)]*)/invalidate_bdev(\1)/g' $file; done Signed-off-by: Peter Zijlstra Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds