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iversion: add a routine to update a raw value with a larger one

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Under ceph, clients can be independently updating iversion themselves,
while working under comprehensive sets of caps on an inode. In that
situation we always want to prefer the largest value of a change
attribute. Add a new function that will update a raw value with a larger
one, but otherwise leave it alone.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
This commit is contained in:
Jeff Layton 2019-06-05 17:24:22 -04:00 committed by Ilya Dryomov
parent 58981784a6
commit 441d367644
1 changed files with 24 additions and 0 deletions
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24
include/linux/iversion.h
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@ -112,6 +112,30 @@ inode_peek_iversion_raw(const struct inode *inode)
return atomic64_read(&inode->i_version);
}
/**
* inode_set_max_iversion_raw - update i_version new value is larger
* @inode: inode to set
* @val: new i_version to set
*
* Some self-managed filesystems (e.g Ceph) will only update the i_version
* value if the new value is larger than the one we already have.
*/
static inline void
inode_set_max_iversion_raw(struct inode *inode, u64 val)
{
u64 cur, old;
cur = inode_peek_iversion_raw(inode);
for (;;) {
if (cur > val)
break;
old = atomic64_cmpxchg(&inode->i_version, cur, val);
if (likely(old == cur))
break;
cur = old;
}
}
/**
* inode_set_iversion - set i_version to a particular value
* @inode: inode to set