Thanks, Paul
Paul Clements wrote:
OK, so here it is. The changes from the previous patch are, basically:
1) The patch is a little less intrusive now. The diffs against md/raid1 are smaller as more of the bitmap handling code is now isolated in the bitmap.c and bitmap.h files. Also, the diff against mdadm, while now a little larger, is less intrusive as I've created a bitmap.c file in the mdadm sources, as well.
2) The bitmap file I/O routines have been totally rewritten and are now much simpler. We now use read_cache_page, prepare_write/commit_write (to extend the file at init time, if necessary), and bmap/submit_bh (to "sync" the file pages). The use of bmap and submit_bh is due to a limitation in jbd that allows only one ongoing transaction per process (see comment in bitmap.c regarding current->journal_info).
3) The bitmap file now has a superblock containing various configuration
information. The bitmap superblock is checked against the md superblock
when the array is assembled.
Options have been added to mdadm to create and examine bitmap files, and also to specify the bitmap file to be used with an array:
Create a bitmap file: --------------------
# mdadm --create-bitmap=65536,3,580480 /tmp/bitmap --force
(this creates a bitmap file with a chunksize of 64KB, a 3 second bitmap daemon sleep period, and a bitmap (initially dirtied) which is appropriate for use with an array of 580480 blocks)
Examine a bitmap file: ---------------------
# mdadm --examine-bitmap /tmp/bitmap (or just: mdadm -X /tmp/bitmap) Filename : /tmp/bitmap Magic : 6d746962 Version : 2 UUID : 997cb579.99d31d20.3014cae8.4bb4bf9d Events : 5 State : OK Chunksize : 4 KB Daemon : 5s flush period Array Size : 580480 (566.88 MiB 594.41 MB) Bitmap : 145120 bits (chunks), 145120 dirty (100.0%)
(in addition, mdadm -D <array> gives the bitmap information if a bitmap is attached to the array)
Create or Assemble array using a bitmap: ---------------------------------------
# mdadm -C /dev/md2 -n 2 -l 1 --bitmap=/tmp/bitmap /dev/sda5 missing
# mdadm -A /dev/md2 --bitmap=/tmp/bitmap /dev/sda5 /dev/sdb5
Patch Location: --------------
Patch vs. linux 2.6.5-rc2 ========================= http://parisc-linux.org/~jejb/md_bitmap/md_bitmap_2_31_2_6_5_RC2.diff
Patch vs. mdadm 1.5.0 ===================== http://parisc-linux.org/~jejb/md_bitmap/mdadm_1_5_0-bitmap.diff
(no async write patch has been generated, these patches contain only the bitmap code)
Notes: -----
1) an is_create flag was added to do_md_run to tell bitmap_create whether we are creating or just assembling the array -- this is necessary since 0.90 superblocks do not have a UUID until one is generated randomly at array creation time, therefore, we must set the bitmap UUID equal to this newly generated array UUID when the array is created
2) bitmap.h was not included in the mdadm patch, but a link (or copy) must be made to the kernel's include/linux/raid/bitmap.h file in order to build mdadm now
3) code was added to mdadm to allow creation of arrays with non-persistent superblocks (also, device size calculation with non-persistent superblocks was fixed)
4) a fix was made to the hot_remove code to allow a faulty device to be removed
5) various typo and minor bug fixes were also included in the patches - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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