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shmem: support RENAME_WHITEOUT

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Allocate a dentry, initialize it with a whiteout and hash it in the place
of the old dentry.  Later the old dentry will be moved away and the
whiteout will remain.

i_mutex protects agains concurrent readdir.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
This commit is contained in:
Miklos Szeredi 2014-10-24 00:14:37 +02:00
parent cd808deced
commit 46fdb794e3
1 changed files with 35 additions and 1 deletions
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36
mm/shmem.c
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@ -2345,6 +2345,32 @@ static int shmem_exchange(struct inode *old_dir, struct dentry *old_dentry, stru
return 0;
}
static int shmem_whiteout(struct inode *old_dir, struct dentry *old_dentry)
{
struct dentry *whiteout;
int error;
whiteout = d_alloc(old_dentry->d_parent, &old_dentry->d_name);
if (!whiteout)
return -ENOMEM;
error = shmem_mknod(old_dir, whiteout,
S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV);
dput(whiteout);
if (error)
return error;
/*
* Cheat and hash the whiteout while the old dentry is still in
* place, instead of playing games with FS_RENAME_DOES_D_MOVE.
*
* d_lookup() will consistently find one of them at this point,
* not sure which one, but that isn't even important.
*/
d_rehash(whiteout);
return 0;
}
/*
* The VFS layer already does all the dentry stuff for rename,
* we just have to decrement the usage count for the target if
@ -2356,7 +2382,7 @@ static int shmem_rename2(struct inode *old_dir, struct dentry *old_dentry, struc
struct inode *inode = old_dentry->d_inode;
int they_are_dirs = S_ISDIR(inode->i_mode);
if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
return -EINVAL;
if (flags & RENAME_EXCHANGE)
@ -2365,6 +2391,14 @@ static int shmem_rename2(struct inode *old_dir, struct dentry *old_dentry, struc
if (!simple_empty(new_dentry))
return -ENOTEMPTY;
if (flags & RENAME_WHITEOUT) {
int error;
error = shmem_whiteout(old_dir, old_dentry);
if (error)
return error;
}
if (new_dentry->d_inode) {
(void) shmem_unlink(new_dir, new_dentry);
if (they_are_dirs) {