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Refactor and fix rename code

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- Create source whiteout only when needed
- Fix missing source whiteout when destination is whiteout
- Try the EXCHANGE trick also when NOREPLACE is set

Signed-off-by: Tuupertunut <tuupertunut@outlook.com>
This commit is contained in:
Tuupertunut 2022-06-07 19:24:09 +03:00
parent 878cb0ccad
commit 6a0de4a5b0
1 changed files with 38 additions and 33 deletions
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53
main.c
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@ -4538,11 +4538,15 @@ ovl_rename_direct (fuse_req_t req, fuse_ino_t parent, const char *name,
if (node == NULL)
goto error;
/* If NOREPLACE flag is given, check if we should throw an error now.
If not, just remove the flag as it might cause problems with replacing whiteouts later. */
if (flags & RENAME_NOREPLACE && destnode && !destnode->whiteout)
{
errno = EEXIST;
goto error;
}
else
flags = flags & ~RENAME_NOREPLACE;
if (destnode)
{
@ -4597,17 +4601,6 @@ ovl_rename_direct (fuse_req_t req, fuse_ino_t parent, const char *name,
}
}
/* If the destnode is a whiteout, first attempt to EXCHANGE the source and the destination,
so that with one operation we get both the rename and the whiteout created. */
if (destnode_is_whiteout)
{
ret = direct_renameat2 (srcfd, name, destfd, newname, flags|RENAME_EXCHANGE);
if (ret == 0)
goto done;
/* If it fails for any reason, fallback to the more articulated method. */
}
/* If the node is a directory we must ensure there is no whiteout at the
destination, otherwise the renameat2 will fail. Create a .wh.$NAME style
whiteout file until the renameat2 is completed. */
@ -4619,39 +4612,51 @@ ovl_rename_direct (fuse_req_t req, fuse_ino_t parent, const char *name,
unlinkat (destfd, newname, 0);
}
/* Try to create the whiteout atomically, if it fails do the
rename+mknod separately. */
bool src_needs_whiteout = (node->last_layer != get_upper_layer (lo));
if (src_needs_whiteout)
{
/* Trying to atomically both rename and create the whiteout.
If destination is a whiteout, we can EXCHANGE source and destination and reuse the old whiteout.
If not, we can try to atomically create one with the WHITEOUT flag. */
if (destnode_is_whiteout)
ret = direct_renameat2 (srcfd, name, destfd, newname, flags|RENAME_EXCHANGE);
else
{
if (! can_mknod)
{
ret = -1;
errno = EPERM;
}
else
{
ret = direct_renameat2 (srcfd, name, destfd,
newname, flags|RENAME_WHITEOUT);
ret = direct_renameat2 (srcfd, name, destfd, newname, flags|RENAME_WHITEOUT);
}
/* If the destination is a whiteout, just overwrite it. */
if (ret < 0 && errno == EEXIST)
ret = direct_renameat2 (srcfd, name, destfd, newname, flags & ~RENAME_NOREPLACE);
/* If atomic whiteout creation failed, fall back to separate rename and whiteout creation. */
if (ret < 0)
{
ret = direct_renameat2 (srcfd, name, destfd,
newname, flags);
ret = direct_renameat2 (srcfd, name, destfd, newname, flags);
if (ret < 0)
goto error;
ret = create_whiteout (lo, pnode, name, false, true);
if (ret < 0)
goto error;
pnode->loaded = 0;
}
}
else
{
ret = direct_renameat2 (srcfd, name, destfd, newname, flags);
if (ret < 0)
goto error;
}
pnode->loaded = 0;
/* If the destination was .wh. style whiteout, it was not replaced automatically, so delete it. */
if (delete_whiteout (lo, destfd, NULL, newname) < 0)
goto error;
done:
hash_delete (pnode->children, node);
free (node->name);