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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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6
fs/overlayfs/copy_up.c
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@@ -125,6 +125,7 @@ static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len)
struct file *new_file;
loff_t old_pos = 0;
loff_t new_pos = 0;
loff_t cloned;
int error = 0;
if (len == 0)
@@ -141,11 +142,10 @@ static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len)
}
/* Try to use clone_file_range to clone up within the same fs */
error = do_clone_file_range(old_file, 0, new_file, 0, len);
if (!error)
cloned = do_clone_file_range(old_file, 0, new_file, 0, len);
if (cloned == len)
goto out;
/* Couldn't clone, so now we try to copy the data */
error = 0;
/* FIXME: copy up sparse files efficiently */
while (len) {