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ovl: convert ovl_real_fdget() callers to ovl_real_file()
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Stop using struct fd to return a real file from ovl_real_fdget(),
because we no longer return a temporary file object and the callers
always get a borrowed file reference.

Rename the helper to ovl_real_file(), return a borrowed reference of
the real file that is referenced from the overlayfs file or an error.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
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Amir Goldstein committed Nov 15, 2024
1 parent 4333e42 commit d66907b
Showing 1 changed file with 59 additions and 84 deletions.
143 changes: 59 additions & 84 deletions fs/overlayfs/file.c
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Original file line number Diff line number Diff line change
Expand Up @@ -195,16 +195,6 @@ static struct file *ovl_real_file(const struct file *file)
return ovl_real_file_path(file, &realpath);
}

static int ovl_real_fdget(const struct file *file, struct fd *real)
{
struct file *f = ovl_real_file(file);

if (IS_ERR(f))
return PTR_ERR(f);
real->word = (unsigned long)f;
return 0;
}

static int ovl_open(struct inode *inode, struct file *file)
{
struct dentry *dentry = file_dentry(file);
Expand Down Expand Up @@ -253,7 +243,7 @@ static int ovl_release(struct inode *inode, struct file *file)
static loff_t ovl_llseek(struct file *file, loff_t offset, int whence)
{
struct inode *inode = file_inode(file);
struct fd real;
struct file *realfile;
const struct cred *old_cred;
loff_t ret;

Expand All @@ -269,9 +259,9 @@ static loff_t ovl_llseek(struct file *file, loff_t offset, int whence)
return vfs_setpos(file, 0, 0);
}

ret = ovl_real_fdget(file, &real);
if (ret)
return ret;
realfile = ovl_real_file(file);
if (IS_ERR(realfile))
return PTR_ERR(realfile);

/*
* Overlay file f_pos is the master copy that is preserved
Expand All @@ -281,17 +271,15 @@ static loff_t ovl_llseek(struct file *file, loff_t offset, int whence)
* files, so we use the real file to perform seeks.
*/
ovl_inode_lock(inode);
fd_file(real)->f_pos = file->f_pos;
realfile->f_pos = file->f_pos;

old_cred = ovl_override_creds(inode->i_sb);
ret = vfs_llseek(fd_file(real), offset, whence);
ret = vfs_llseek(realfile, offset, whence);
ovl_revert_creds(old_cred);

file->f_pos = fd_file(real)->f_pos;
file->f_pos = realfile->f_pos;
ovl_inode_unlock(inode);

fdput(real);

return ret;
}

Expand Down Expand Up @@ -337,8 +325,7 @@ static void ovl_file_accessed(struct file *file)
static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter)
{
struct file *file = iocb->ki_filp;
struct fd real;
ssize_t ret;
struct file *realfile;
struct backing_file_ctx ctx = {
.cred = ovl_creds(file_inode(file)->i_sb),
.accessed = ovl_file_accessed,
Expand All @@ -347,22 +334,19 @@ static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter)
if (!iov_iter_count(iter))
return 0;

ret = ovl_real_fdget(file, &real);
if (ret)
return ret;

ret = backing_file_read_iter(fd_file(real), iter, iocb, iocb->ki_flags,
&ctx);
fdput(real);
realfile = ovl_real_file(file);
if (IS_ERR(realfile))
return PTR_ERR(realfile);

return ret;
return backing_file_read_iter(realfile, iter, iocb, iocb->ki_flags,
&ctx);
}

static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
{
struct file *file = iocb->ki_filp;
struct inode *inode = file_inode(file);
struct fd real;
struct file *realfile;
ssize_t ret;
int ifl = iocb->ki_flags;
struct backing_file_ctx ctx = {
Expand All @@ -377,8 +361,9 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
/* Update mode */
ovl_copyattr(inode);

ret = ovl_real_fdget(file, &real);
if (ret)
realfile = ovl_real_file(file);
ret = PTR_ERR(realfile);
if (IS_ERR(realfile))
goto out_unlock;

if (!ovl_should_sync(OVL_FS(inode->i_sb)))
Expand All @@ -389,8 +374,7 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
* this property in case it is set by the issuer.
*/
ifl &= ~IOCB_DIO_CALLER_COMP;
ret = backing_file_write_iter(fd_file(real), iter, iocb, ifl, &ctx);
fdput(real);
ret = backing_file_write_iter(realfile, iter, iocb, ifl, &ctx);

out_unlock:
inode_unlock(inode);
Expand All @@ -402,39 +386,38 @@ static ssize_t ovl_splice_read(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe, size_t len,
unsigned int flags)
{
struct fd real;
struct file *realfile;
ssize_t ret;
struct backing_file_ctx ctx = {
.cred = ovl_creds(file_inode(in)->i_sb),
.accessed = ovl_file_accessed,
};
struct kiocb iocb;

ret = ovl_real_fdget(in, &real);
if (ret)
return ret;
realfile = ovl_real_file(in);
if (IS_ERR(realfile))
return PTR_ERR(realfile);

init_sync_kiocb(&iocb, in);
iocb.ki_pos = *ppos;
ret = backing_file_splice_read(fd_file(real), &iocb, pipe, len, flags, &ctx);
ret = backing_file_splice_read(realfile, &iocb, pipe, len, flags, &ctx);
*ppos = iocb.ki_pos;
fdput(real);

return ret;
}

/*
* Calling iter_file_splice_write() directly from overlay's f_op may deadlock
* due to lock order inversion between pipe->mutex in iter_file_splice_write()
* and file_start_write(fd_file(real)) in ovl_write_iter().
* and file_start_write(realfile) in ovl_write_iter().
*
* So do everything ovl_write_iter() does and call iter_file_splice_write() on
* the real file.
*/
static ssize_t ovl_splice_write(struct pipe_inode_info *pipe, struct file *out,
loff_t *ppos, size_t len, unsigned int flags)
{
struct fd real;
struct file *realfile;
struct inode *inode = file_inode(out);
ssize_t ret;
struct backing_file_ctx ctx = {
Expand All @@ -447,16 +430,15 @@ static ssize_t ovl_splice_write(struct pipe_inode_info *pipe, struct file *out,
/* Update mode */
ovl_copyattr(inode);

ret = ovl_real_fdget(out, &real);
if (ret)
realfile = ovl_real_file(out);
ret = PTR_ERR(realfile);
if (IS_ERR(realfile))
goto out_unlock;

init_sync_kiocb(&iocb, out);
iocb.ki_pos = *ppos;
ret = backing_file_splice_write(pipe, fd_file(real), &iocb, len, flags, &ctx);
ret = backing_file_splice_write(pipe, realfile, &iocb, len, flags, &ctx);
*ppos = iocb.ki_pos;
fdput(real);


out_unlock:
inode_unlock(inode);
Expand Down Expand Up @@ -508,7 +490,7 @@ static int ovl_mmap(struct file *file, struct vm_area_struct *vma)
static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
{
struct inode *inode = file_inode(file);
struct fd real;
struct file *realfile;
const struct cred *old_cred;
int ret;

Expand All @@ -519,19 +501,18 @@ static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len
if (ret)
goto out_unlock;

ret = ovl_real_fdget(file, &real);
if (ret)
realfile = ovl_real_file(file);
ret = PTR_ERR(realfile);
if (IS_ERR(realfile))
goto out_unlock;

old_cred = ovl_override_creds(file_inode(file)->i_sb);
ret = vfs_fallocate(fd_file(real), mode, offset, len);
ret = vfs_fallocate(realfile, mode, offset, len);
ovl_revert_creds(old_cred);

/* Update size */
ovl_file_modified(file);

fdput(real);

out_unlock:
inode_unlock(inode);

Expand All @@ -540,20 +521,18 @@ static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len

static int ovl_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
{
struct fd real;
struct file *realfile;
const struct cred *old_cred;
int ret;

ret = ovl_real_fdget(file, &real);
if (ret)
return ret;
realfile = ovl_real_file(file);
if (IS_ERR(realfile))
return PTR_ERR(realfile);

old_cred = ovl_override_creds(file_inode(file)->i_sb);
ret = vfs_fadvise(fd_file(real), offset, len, advice);
ret = vfs_fadvise(realfile, offset, len, advice);
ovl_revert_creds(old_cred);

fdput(real);

return ret;
}

Expand All @@ -568,7 +547,7 @@ static loff_t ovl_copyfile(struct file *file_in, loff_t pos_in,
loff_t len, unsigned int flags, enum ovl_copyop op)
{
struct inode *inode_out = file_inode(file_out);
struct fd real_in, real_out;
struct file *realfile_in, *realfile_out;
const struct cred *old_cred;
loff_t ret;

Expand All @@ -581,31 +560,31 @@ static loff_t ovl_copyfile(struct file *file_in, loff_t pos_in,
goto out_unlock;
}

ret = ovl_real_fdget(file_out, &real_out);
if (ret)
realfile_out = ovl_real_file(file_out);
ret = PTR_ERR(realfile_out);
if (IS_ERR(realfile_out))
goto out_unlock;

ret = ovl_real_fdget(file_in, &real_in);
if (ret) {
fdput(real_out);
realfile_in = ovl_real_file(file_in);
ret = PTR_ERR(realfile_in);
if (IS_ERR(realfile_in))
goto out_unlock;
}

old_cred = ovl_override_creds(file_inode(file_out)->i_sb);
switch (op) {
case OVL_COPY:
ret = vfs_copy_file_range(fd_file(real_in), pos_in,
fd_file(real_out), pos_out, len, flags);
ret = vfs_copy_file_range(realfile_in, pos_in,
realfile_out, pos_out, len, flags);
break;

case OVL_CLONE:
ret = vfs_clone_file_range(fd_file(real_in), pos_in,
fd_file(real_out), pos_out, len, flags);
ret = vfs_clone_file_range(realfile_in, pos_in,
realfile_out, pos_out, len, flags);
break;

case OVL_DEDUPE:
ret = vfs_dedupe_file_range_one(fd_file(real_in), pos_in,
fd_file(real_out), pos_out, len,
ret = vfs_dedupe_file_range_one(realfile_in, pos_in,
realfile_out, pos_out, len,
flags);
break;
}
Expand All @@ -614,9 +593,6 @@ static loff_t ovl_copyfile(struct file *file_in, loff_t pos_in,
/* Update size */
ovl_file_modified(file_out);

fdput(real_in);
fdput(real_out);

out_unlock:
inode_unlock(inode_out);

Expand Down Expand Up @@ -660,20 +636,19 @@ static loff_t ovl_remap_file_range(struct file *file_in, loff_t pos_in,

static int ovl_flush(struct file *file, fl_owner_t id)
{
struct fd real;
struct file *realfile;
const struct cred *old_cred;
int err;
int err = 0;

err = ovl_real_fdget(file, &real);
if (err)
return err;
realfile = ovl_real_file(file);
if (IS_ERR(realfile))
return PTR_ERR(realfile);

if (fd_file(real)->f_op->flush) {
if (realfile->f_op->flush) {
old_cred = ovl_override_creds(file_inode(file)->i_sb);
err = fd_file(real)->f_op->flush(fd_file(real), id);
err = realfile->f_op->flush(realfile, id);
ovl_revert_creds(old_cred);
}
fdput(real);

return err;
}
Expand Down

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