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fs: have setattr_copy handle multigrain timestamps appropriately

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The setattr codepath is still using coarse-grained timestamps, even on
multigrain filesystems. To fix this, fetch the timestamp for ctime
updates later, at the point where the assignment occurs in setattr_copy.

On a multigrain inode, ignore the ia_ctime in the attrs, and always
update the ctime to the current clock value. Update the atime and mtime
with the same value (if needed) unless they are being set to other
specific values, a'la utimes().

Do not do this universally however, as some filesystems (e.g. most
networked fs) want to do an explicit update elsewhere before updating
the local inode.

Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Tested-by: Randy Dunlap <rdunlap@infradead.org> # documentation bits
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/r/20241002-mgtime-v10-4-d1c4717f5284@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Jeff Layton 2024-10-02 17:27:19 -04:00 committed by Christian Brauner
parent 4e40eff0b5
commit b82f92d5dd
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GPG Key ID: 91C61BC06578DCA2
1 changed files with 46 additions and 6 deletions
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52
fs/attr.c
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@ -271,6 +271,42 @@ out_big:
}
EXPORT_SYMBOL(inode_newsize_ok);
/**
* setattr_copy_mgtime - update timestamps for mgtime inodes
* @inode: inode timestamps to be updated
* @attr: attrs for the update
*
* With multigrain timestamps, take more care to prevent races when
* updating the ctime. Always update the ctime to the very latest using
* the standard mechanism, and use that to populate the atime and mtime
* appropriately (unless those are being set to specific values).
*/
static void setattr_copy_mgtime(struct inode *inode, const struct iattr *attr)
{
unsigned int ia_valid = attr->ia_valid;
struct timespec64 now;
/*
* If the ctime isn't being updated then nothing else should be
* either.
*/
if (!(ia_valid & ATTR_CTIME)) {
WARN_ON_ONCE(ia_valid & (ATTR_ATIME|ATTR_MTIME));
return;
}
now = inode_set_ctime_current(inode);
if (ia_valid & ATTR_ATIME_SET)
inode_set_atime_to_ts(inode, attr->ia_atime);
else if (ia_valid & ATTR_ATIME)
inode_set_atime_to_ts(inode, now);
if (ia_valid & ATTR_MTIME_SET)
inode_set_mtime_to_ts(inode, attr->ia_mtime);
else if (ia_valid & ATTR_MTIME)
inode_set_mtime_to_ts(inode, now);
}
/**
* setattr_copy - copy simple metadata updates into the generic inode
* @idmap: idmap of the mount the inode was found from
@ -303,12 +339,6 @@ void setattr_copy(struct mnt_idmap *idmap, struct inode *inode,
i_uid_update(idmap, attr, inode);
i_gid_update(idmap, attr, inode);
if (ia_valid & ATTR_ATIME)
inode_set_atime_to_ts(inode, attr->ia_atime);
if (ia_valid & ATTR_MTIME)
inode_set_mtime_to_ts(inode, attr->ia_mtime);
if (ia_valid & ATTR_CTIME)
inode_set_ctime_to_ts(inode, attr->ia_ctime);
if (ia_valid & ATTR_MODE) {
umode_t mode = attr->ia_mode;
if (!in_group_or_capable(idmap, inode,
@ -316,6 +346,16 @@ void setattr_copy(struct mnt_idmap *idmap, struct inode *inode,
mode &= ~S_ISGID;
inode->i_mode = mode;
}
if (is_mgtime(inode))
return setattr_copy_mgtime(inode, attr);
if (ia_valid & ATTR_ATIME)
inode_set_atime_to_ts(inode, attr->ia_atime);
if (ia_valid & ATTR_MTIME)
inode_set_mtime_to_ts(inode, attr->ia_mtime);
if (ia_valid & ATTR_CTIME)
inode_set_ctime_to_ts(inode, attr->ia_ctime);
}
EXPORT_SYMBOL(setattr_copy);