From: Miklos Szeredi <mszeredi@xxxxxxx>
This adds a new RENAME_WHITEOUT flag. This flag makes rename() create a
whiteout of source. The whiteout creation is atomic relative to the
rename.
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
---
fs/ext4/namei.c | 99 ++++++++++++++++++++++++++++++++++++++++---------
fs/namei.c | 8 +++-
include/linux/fs.h | 7 ++++
include/uapi/linux/fs.h | 1 +
4 files changed, 95 insertions(+), 20 deletions(-)
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 1cb84f78909e..f782831b19dc 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -3148,6 +3148,39 @@ static void ext4_update_dir_count(handle_t *handle, struct ext4_renament *ent)
}
}
+static struct inode *ext4_whiteout_for_rename(struct ext4_renament *ent,
+ int credits, handle_t **h)
+{
+ struct inode *wh;
+ handle_t *handle;
+ int retries = 0;
+
+ /*
+ * for inode block, sb block, group summaries,
+ * and inode bitmap
+ */
+ credits += (EXT4_MAXQUOTAS_TRANS_BLOCKS(ent->dir->i_sb) +
+ EXT4_XATTR_TRANS_BLOCKS + 4);
+retry:
+ wh = ext4_new_inode_start_handle(ent->dir, S_IFCHR | WHITEOUT_MODE,
+ &ent->dentry->d_name, 0, NULL,
+ EXT4_HT_DIR, credits);
+
+ handle = ext4_journal_current_handle();
+ if (IS_ERR(wh)) {
+ if (handle)
+ ext4_journal_stop(handle);
+ if (PTR_ERR(wh) == -ENOSPC &&
+ ext4_should_retry_alloc(ent->dir->i_sb, &retries))
+ goto retry;
+ } else {
+ *h = handle;
+ init_special_inode(wh, wh->i_mode, WHITEOUT_DEV);
+ wh->i_op = &ext4_special_inode_operations;
+ }
+ return wh;
+}
+
/*
* Anybody can rename anything with this: the permission checks are left to the
* higher-level routines.
@@ -3156,8 +3189,9 @@ static void ext4_update_dir_count(handle_t *handle, struct ext4_renament *ent)
* while new_{dentry,inode) refers to the destination dentry/inode
* This comes from rename(const char *oldpath, const char *newpath)
*/
-static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
- struct inode *new_dir, struct dentry *new_dentry)
+static int ext4_simple_rename(struct inode *old_dir, struct dentry *old_dentry,
+ struct inode *new_dir, struct dentry *new_dentry,
+ unsigned int flags)
{
handle_t *handle = NULL;
struct ext4_renament old = {
@@ -3171,6 +3205,9 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
.inode = new_dentry->d_inode,
};
int retval;
+ struct inode *whiteout = NULL;
+ int credits;
+ u8 old_file_type;
dquot_initialize(old.dir);
dquot_initialize(new.dir);
@@ -3202,11 +3239,17 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
if (new.inode && !test_opt(new.dir->i_sb, NO_AUTO_DA_ALLOC))
ext4_alloc_da_blocks(old.inode);
- handle = ext4_journal_start(old.dir, EXT4_HT_DIR,
- (2 * EXT4_DATA_TRANS_BLOCKS(old.dir->i_sb) +
- EXT4_INDEX_EXTRA_TRANS_BLOCKS + 2));
- if (IS_ERR(handle))
- return PTR_ERR(handle);
+ credits = (2 * EXT4_DATA_TRANS_BLOCKS(old.dir->i_sb) +
+ EXT4_INDEX_EXTRA_TRANS_BLOCKS + 2);
+ if (!(flags & RENAME_WHITEOUT)) {
+ handle = ext4_journal_start(old.dir, EXT4_HT_DIR, credits);
+ if (IS_ERR(handle))
+ return PTR_ERR(handle);
+ } else {
+ whiteout = ext4_whiteout_for_rename(&old, credits, &handle);
+ if (IS_ERR(whiteout))
+ return PTR_ERR(whiteout);
+ }
if (IS_DIRSYNC(old.dir) || IS_DIRSYNC(new.dir))
ext4_handle_sync(handle);
@@ -3225,13 +3268,21 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
if (retval)
goto end_rename;
}
+ old_file_type = old.de->file_type;
+ if (whiteout) {
+ retval = ext4_setent(handle, &old, whiteout->i_ino,
+ EXT4_FT_CHRDEV);
+ if (retval)
+ goto end_rename;
+ ext4_mark_inode_dirty(handle, whiteout);
+ }
if (!new.bh) {
retval = ext4_add_entry(handle, new.dentry, old.inode);
if (retval)
goto end_rename;
} else {
retval = ext4_setent(handle, &new,
- old.inode->i_ino, old.de->file_type);
+ old.inode->i_ino, old_file_type);
if (retval)
goto end_rename;
}
@@ -3243,10 +3294,12 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
old.inode->i_ctime = ext4_current_time(old.inode);
ext4_mark_inode_dirty(handle, old.inode);
- /*
- * ok, that's it
- */
- ext4_rename_delete(handle, &old);
+ if (!whiteout) {
+ /*
+ * ok, that's it
+ */
+ ext4_rename_delete(handle, &old);
+ }
if (new.inode) {
ext4_dec_count(handle, new.inode);
@@ -3282,6 +3335,12 @@ end_rename:
brelse(old.dir_bh);
brelse(old.bh);
brelse(new.bh);
+ if (whiteout) {
+ if (retval)
+ drop_nlink(whiteout);
+ unlock_new_inode(whiteout);
+ iput(whiteout);
+ }
if (handle)
ext4_journal_stop(handle);
return retval;
@@ -3403,22 +3462,26 @@ end_rename:
return retval;
}
+static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
+ struct inode *new_dir, struct dentry *new_dentry)
+{
+ return ext4_simple_rename(old_dir, old_dentry, new_dir, new_dentry, 0);
+}
+
static int ext4_rename2(struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry,
unsigned int flags)
{
- if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
+ if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
return -EINVAL;
if (flags & RENAME_EXCHANGE) {
return ext4_cross_rename(old_dir, old_dentry,
new_dir, new_dentry);
}
- /*
- * Existence checking was done by the VFS, otherwise "RENAME_NOREPLACE"
- * is equivalent to regular rename.
- */
- return ext4_rename(old_dir, old_dentry, new_dir, new_dentry);
+
+ return ext4_simple_rename(old_dir, old_dentry,
+ new_dir, new_dentry, flags);
}
/*
diff --git a/fs/namei.c b/fs/namei.c
index 413d7c138e95..adaa73d91173 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4186,12 +4186,16 @@ SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname,
bool should_retry = false;
int error;
- if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
+ if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
return -EINVAL;
- if ((flags & RENAME_NOREPLACE) && (flags & RENAME_EXCHANGE))
+ if ((flags & (RENAME_NOREPLACE | RENAME_WHITEOUT)) &&
+ (flags & RENAME_EXCHANGE))
return -EINVAL;
+ if ((flags & RENAME_WHITEOUT) && !capable(CAP_MKNOD))
+ return -EPERM;
+
retry:
from = user_path_parent(olddfd, oldname, &oldnd, lookup_flags);
if (IS_ERR(from)) {
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 88ec7a2878bc..48d3bd908b5d 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -228,6 +228,13 @@ typedef void (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
#define WHITEOUT_DEV 0
/*
+ * Whiteout is represented by a char device. The following constants define the
+ * mode and device number to use.
+ */
+#define WHITEOUT_MODE 0
+#define WHITEOUT_DEV 0
+
+/*
* This is the Inode Attributes structure, used for notify_change(). It
* uses the above definitions as flags, to know which values have changed.
* Also, in this manner, a Filesystem can look at only the values it cares
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index ca1a11bb4443..3735fa0a6784 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -37,6 +37,7 @@
#define RENAME_NOREPLACE (1 << 0) /* Don't overwrite target */
#define RENAME_EXCHANGE (1 << 1) /* Exchange source and dest */
+#define RENAME_WHITEOUT (1 << 2) /* Whiteout source */
struct fstrim_range {
__u64 start;
--
1.8.1.4
--
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