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vfs: make remap_file_range functions take and return bytes completed

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Change the remap_file_range functions to take a number of bytes to
operate upon and return the number of bytes they operated on.  This is a
requirement for allowing fs implementations to return short clone/dedupe
results to the user, which will enable us to obey resource limits in a
graceful manner.

A subsequent patch will enable copy_file_range to signal to the
->clone_file_range implementation that it can handle a short length,
which will be returned in the function's return value.  For now the
short return is not implemented anywhere so the behavior won't change --
either copy_file_range manages to clone the entire range or it tries an
alternative.

Neither clone ioctl can take advantage of this, alas.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
This commit is contained in:
Darrick J. Wong
2018-10-30 10:41:49 +11:00
committed by Dave Chinner
parent 8dde90bca6
commit 42ec3d4c02
18 changed files with 108 additions and 82 deletions
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12
fs/overlayfs/file.c
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@@ -434,14 +434,14 @@ enum ovl_copyop {
OVL_DEDUPE,
};
static ssize_t ovl_copyfile(struct file *file_in, loff_t pos_in,
static loff_t ovl_copyfile(struct file *file_in, loff_t pos_in,
struct file *file_out, loff_t pos_out,
u64 len, unsigned int flags, enum ovl_copyop op)
loff_t len, unsigned int flags, enum ovl_copyop op)
{
struct inode *inode_out = file_inode(file_out);
struct fd real_in, real_out;
const struct cred *old_cred;
ssize_t ret;
loff_t ret;
ret = ovl_real_fdget(file_out, &real_out);
if (ret)
@@ -489,9 +489,9 @@ static ssize_t ovl_copy_file_range(struct file *file_in, loff_t pos_in,
OVL_COPY);
}
static int ovl_remap_file_range(struct file *file_in, loff_t pos_in,
struct file *file_out, loff_t pos_out,
u64 len, unsigned int remap_flags)
static loff_t ovl_remap_file_range(struct file *file_in, loff_t pos_in,
struct file *file_out, loff_t pos_out,
loff_t len, unsigned int remap_flags)
{
enum ovl_copyop op;