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Message-ID: <20190215223925.GO32253@magnolia>
Date: Fri, 15 Feb 2019 14:39:25 -0800
From: "Darrick J. Wong" <darrick.wong@...cle.com>
To: clm@...com, josef@...icpanda.com, dsterba@...e.com,
viro@...iv.linux.org.uk, jack@...e.com, tytso@....edu,
adilger.kernel@...ger.ca, jaegeuk@...nel.org, yuchao0@...wei.com,
hughd@...gle.com, hch@...radead.org
Cc: richard@....at, dedekind1@...il.com, adrian.hunter@...el.com,
linux-xfs@...r.kernel.org, linux-btrfs@...r.kernel.org,
linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net,
linux-mtd@...ts.infradead.org, linux-mm@...ck.org,
amir73il@...il.com
Subject: [PATCH v2] vfs: don't decrement i_nlink in d_tmpfile
From: Darrick J. Wong <darrick.wong@...cle.com>
d_tmpfile was introduced to instantiate an inode in the dentry cache as
a temporary file. This helper decrements the inode's nlink count and
dirties the inode, presumably so that filesystems could call new_inode
to create a new inode with nlink == 1 and then call d_tmpfile which will
decrement nlink.
However, this doesn't play well with XFS, which needs to allocate,
initialize, and insert a tempfile inode on its unlinked list in a single
transaction. In order to maintain referential integrity of the XFS
metadata, we cannot have an inode on the unlinked list with nlink >= 1.
XFS and btrfs hack around d_tmpfile's behavior by creating the inode
with nlink == 0 and then incrementing it just prior to calling
d_tmpfile, anticipating that it will be reset to 0.
Everywhere else, it appears that nlink updates and persistence is
the responsibility of individual filesystems. Therefore, move the nlink
decrement out of d_tmpfile into the callers, and require that callers
only pass in inodes with nlink already set to 0.
Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
---
v2: convert BUG_ON to WARN_ON per review comment
---
fs/btrfs/inode.c | 8 --------
fs/dcache.c | 10 ++++++----
fs/ext2/namei.c | 2 +-
fs/ext4/namei.c | 1 +
fs/f2fs/namei.c | 1 +
fs/minix/namei.c | 2 +-
fs/ubifs/dir.c | 1 +
fs/udf/namei.c | 2 +-
fs/xfs/xfs_iops.c | 13 ++-----------
mm/shmem.c | 1 +
10 files changed, 15 insertions(+), 26 deletions(-)
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 5c349667c761..bd189fc50f83 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -10382,14 +10382,6 @@ static int btrfs_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode)
if (ret)
goto out;
- /*
- * We set number of links to 0 in btrfs_new_inode(), and here we set
- * it to 1 because d_tmpfile() will issue a warning if the count is 0,
- * through:
- *
- * d_tmpfile() -> inode_dec_link_count() -> drop_nlink()
- */
- set_nlink(inode, 1);
d_tmpfile(dentry, inode);
unlock_new_inode(inode);
mark_inode_dirty(inode);
diff --git a/fs/dcache.c b/fs/dcache.c
index aac41adf4743..bb349d423055 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -3042,12 +3042,14 @@ void d_genocide(struct dentry *parent)
EXPORT_SYMBOL(d_genocide);
+/*
+ * Instantiate an inode in the dentry cache as a temporary file. Callers must
+ * ensure that @inode has a zero link count.
+ */
void d_tmpfile(struct dentry *dentry, struct inode *inode)
{
- inode_dec_link_count(inode);
- BUG_ON(dentry->d_name.name != dentry->d_iname ||
- !hlist_unhashed(&dentry->d_u.d_alias) ||
- !d_unlinked(dentry));
+ WARN_ON(dentry->d_name.name != dentry->d_iname ||
+ !d_unlinked(dentry) || inode->i_nlink != 0);
spin_lock(&dentry->d_parent->d_lock);
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
dentry->d_name.len = sprintf(dentry->d_iname, "#%llu",
diff --git a/fs/ext2/namei.c b/fs/ext2/namei.c
index 0c26dcc5d850..8542e9ce9677 100644
--- a/fs/ext2/namei.c
+++ b/fs/ext2/namei.c
@@ -117,7 +117,7 @@ static int ext2_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode)
return PTR_ERR(inode);
ext2_set_file_ops(inode);
- mark_inode_dirty(inode);
+ inode_dec_link_count(inode);
d_tmpfile(dentry, inode);
unlock_new_inode(inode);
return 0;
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 2b928eb07fa2..7502432f9816 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -2517,6 +2517,7 @@ static int ext4_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode)
inode->i_op = &ext4_file_inode_operations;
inode->i_fop = &ext4_file_operations;
ext4_set_aops(inode);
+ inode_dec_link_count(inode);
d_tmpfile(dentry, inode);
err = ext4_orphan_add(handle, inode);
if (err)
diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
index 62d9829f3a6a..31a556af5f3a 100644
--- a/fs/f2fs/namei.c
+++ b/fs/f2fs/namei.c
@@ -780,6 +780,7 @@ static int __f2fs_tmpfile(struct inode *dir, struct dentry *dentry,
f2fs_i_links_write(inode, false);
*whiteout = inode;
} else {
+ inode_dec_link_count(inode);
d_tmpfile(dentry, inode);
}
/* link_count was changed by d_tmpfile as well. */
diff --git a/fs/minix/namei.c b/fs/minix/namei.c
index 1a6084d2b02e..3249f86c476a 100644
--- a/fs/minix/namei.c
+++ b/fs/minix/namei.c
@@ -57,7 +57,7 @@ static int minix_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode)
struct inode *inode = minix_new_inode(dir, mode, &error);
if (inode) {
minix_set_inode(inode, 0);
- mark_inode_dirty(inode);
+ inode_dec_link_count(inode);
d_tmpfile(dentry, inode);
}
return error;
diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c
index 5767b373a8ff..7187e4fd7561 100644
--- a/fs/ubifs/dir.c
+++ b/fs/ubifs/dir.c
@@ -419,6 +419,7 @@ static int do_tmpfile(struct inode *dir, struct dentry *dentry,
drop_nlink(inode);
*whiteout = inode;
} else {
+ inode_dec_link_count(inode);
d_tmpfile(dentry, inode);
}
ubifs_assert(c, ui->dirty);
diff --git a/fs/udf/namei.c b/fs/udf/namei.c
index 58cc2414992b..38bd021f9673 100644
--- a/fs/udf/namei.c
+++ b/fs/udf/namei.c
@@ -652,7 +652,7 @@ static int udf_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode)
inode->i_data.a_ops = &udf_aops;
inode->i_op = &udf_file_inode_operations;
inode->i_fop = &udf_file_operations;
- mark_inode_dirty(inode);
+ inode_dec_link_count(inode);
d_tmpfile(dentry, inode);
unlock_new_inode(inode);
return 0;
diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 1efef69a7f1c..f48ffd7a8d3e 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -191,18 +191,9 @@ xfs_generic_create(
xfs_setup_iops(ip);
- if (tmpfile) {
- /*
- * The VFS requires that any inode fed to d_tmpfile must have
- * nlink == 1 so that it can decrement the nlink in d_tmpfile.
- * However, we created the temp file with nlink == 0 because
- * we're not allowed to put an inode with nlink > 0 on the
- * unlinked list. Therefore we have to set nlink to 1 so that
- * d_tmpfile can immediately set it back to zero.
- */
- set_nlink(inode, 1);
+ if (tmpfile)
d_tmpfile(dentry, inode);
- } else
+ else
d_instantiate(dentry, inode);
xfs_finish_inode_setup(ip);
diff --git a/mm/shmem.c b/mm/shmem.c
index 6ece1e2fe76e..4a7810093561 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2818,6 +2818,7 @@ shmem_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode)
error = simple_acl_create(dir, inode);
if (error)
goto out_iput;
+ inode_dec_link_count(inode);
d_tmpfile(dentry, inode);
}
return error;
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