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authorVivek Goyal <vgoyal@redhat.com>2012-08-01 12:24:18 +0200
committerJens Axboe <axboe@kernel.dk>2012-08-01 12:24:18 +0200
commitc83f6bf98dc1f1a194118b3830706cebbebda8c4 (patch)
treeea8fbd925584f784164617964a9f025bda16ed15 /include/linux/blkpg.h
parent4638a83e8615de9c16c39dfed234951d0f468cf1 (diff)
downloadop-kernel-dev-c83f6bf98dc1f1a194118b3830706cebbebda8c4.zip
op-kernel-dev-c83f6bf98dc1f1a194118b3830706cebbebda8c4.tar.gz
block: add partition resize function to blkpg ioctl
Add a new operation code (BLKPG_RESIZE_PARTITION) to the BLKPG ioctl that allows altering the size of an existing partition, even if it is currently in use. This patch converts hd_struct->nr_sects into sequence counter because One might extend a partition while IO is happening to it and update of nr_sects can be non-atomic on 32bit machines with 64bit sector_t. This can lead to issues like reading inconsistent size of a partition. Sequence counter have been used so that readers don't have to take bdev mutex lock as we call sector_in_part() very frequently. Now all the access to hd_struct->nr_sects should happen using sequence counter read/update helper functions part_nr_sects_read/part_nr_sects_write. There is one exception though, set_capacity()/get_capacity(). I think theoritically race should exist there too but this patch does not modify set_capacity()/get_capacity() due to sheer number of call sites and I am afraid that change might break something. I have left that as a TODO item. We can handle it later if need be. This patch does not introduce any new races as such w.r.t set_capacity()/get_capacity(). v2: Add CONFIG_LBDAF test to UP preempt case as suggested by Phillip. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Phillip Susi <psusi@ubuntu.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'include/linux/blkpg.h')
-rw-r--r--include/linux/blkpg.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/blkpg.h b/include/linux/blkpg.h
index faf8a45..a851944 100644
--- a/include/linux/blkpg.h
+++ b/include/linux/blkpg.h
@@ -40,6 +40,7 @@ struct blkpg_ioctl_arg {
/* The subfunctions (for the op field) */
#define BLKPG_ADD_PARTITION 1
#define BLKPG_DEL_PARTITION 2
+#define BLKPG_RESIZE_PARTITION 3
/* Sizes of name fields. Unused at present. */
#define BLKPG_DEVNAMELTH 64
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