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| author |   Dan Williams <dan.j.williams@intel.com> | 2008-06-27 21:44:04 -0700 |
|---|---|---|
| committer | Dan Williams <dan.j.williams@intel.com> | 2008-06-30 17:18:19 -0700 |
| commit | b5470dc5fc18a8ff6517c3bb538d1479e58ecb02 (patch) | |
| tree | 37b0eb3a4691bdbe58dc5c6c73b2dc8d3925b332 /include/linux | |
| parent | md: rationalize raid5 function names (diff) | |
| download | linux-dev-b5470dc5fc18a8ff6517c3bb538d1479e58ecb02.tar.xz linux-dev-b5470dc5fc18a8ff6517c3bb538d1479e58ecb02.zip | |
md: resolve external metadata handling deadlock in md_allow_write
md_allow_write() marks the metadata dirty while holding mddev->lock and then
waits for the write to complete. For externally managed metadata this causes a
deadlock as userspace needs to take the lock to communicate that the metadata
update has completed.
Change md_allow_write() in the 'external' case to start the 'mark active'
operation and then return -EAGAIN. The expected side effects while waiting for
userspace to write 'active' to 'array_state' are holding off reshape (code
currently handles -ENOMEM), cause some 'stripe_cache_size' change requests to
fail, cause some GET_BITMAP_FILE ioctl requests to fall back to GFP_NOIO, and
cause updates to 'raid_disks' to fail. Except for 'stripe_cache_size' changes
these failures can be mitigated by coordinating with mdmon.
md_write_start() still prevents writes from occurring until the metadata
handler has had a chance to take action as it unconditionally waits for
MD_CHANGE_CLEAN to be cleared.
[neilb@suse.de: return -EAGAIN, try GFP_NOIO]
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/raid/md.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/raid/md.h b/include/linux/raid/md.h index b7386ae9d288..dc0e3fcb9f28 100644 --- a/include/linux/raid/md.h +++ b/include/linux/raid/md.h @@ -95,7 +95,7 @@ extern int sync_page_io(struct block_device *bdev, sector_t sector, int size, struct page *page, int rw); extern void md_do_sync(mddev_t *mddev); extern void md_new_event(mddev_t *mddev); -extern void md_allow_write(mddev_t *mddev); +extern int md_allow_write(mddev_t *mddev); extern void md_wait_for_blocked_rdev(mdk_rdev_t *rdev, mddev_t *mddev); #endif /* CONFIG_MD */ |