Re: [PATCH 17/19] xfsprogs: disable truncating of files

Eric Sandeen
2016-04-06T21:42:10Z

On 3/24/16 6:15 AM, jtulak@redhat.com wrote:
> From: Jan Tulak <jtulak@redhat.com>
>
> Unify mkfs.xfs behaviour a bit and never truncate files. If the user
> is trying to mkfs an existing file, we don't want to destroy anything
> he did with the file before (sparse file, allocations...)

Hm, I guess so ... What motivated this change? I see that it
changes behavior, but I'm not sure what it unifies or fixes -
can you explain more?

a bit more below.

> Signed-off-by: Jan Tulak <jtulak@redhat.com>
> ---
> libxfs/init.c | 2 +-
> mkfs/xfs_mkfs.c | 18 +++++++++++-------
> 2 files changed, 12 insertions(+), 8 deletions(-)
>
> diff --git a/libxfs/init.c b/libxfs/init.c
> index 268136f..5f4b6c4 100644
> --- a/libxfs/init.c
> +++ b/libxfs/init.c
> @@ -112,7 +112,7 @@ libxfs_device_open(char *path, int creat, int xflags, int setblksize)
>
> retry:
> flags = (readonly ? O_RDONLY : O_RDWR) | \
> - (creat ? (O_CREAT|O_TRUNC) : 0) | \
> + (creat ? O_CREAT : 0) | \
> (dio ? O_DIRECT : 0) | \
> (excl ? O_EXCL : 0);
>
> diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
> index 9a6ae2c..2bb3b35 100644
> --- a/mkfs/xfs_mkfs.c
> +++ b/mkfs/xfs_mkfs.c
> @@ -1029,15 +1029,19 @@ check_device_type(
> const char *optname)
> {
> struct stat64 statbuf;
> + int statres;
>
> - if (*isfile && (no_size || no_name)) {
> + statres = stat64(name, &statbuf);
> +
> + if (*isfile && statres != 0 && (no_size || no_name)) {

statres !=0 doesn't imply ENOENT; it could be EACCES
or several other errors. You'd need to check errno to know
for sure.

> fprintf(stderr,
> - _("if -%s file then -%s name and -%s size are required\n"),
> - optname, optname, optname);
> + _("if -%s file and the file does not exists, " \

don't need a "\" there, and should read "does not exist"

> + "then -%s name and -%s size are required\n"),

Better, just tab it out if possible, though it's a long line... perhaps:

_("-%s file requires -%s name and -%s size for file creation\n");

or something like that.

> + optname, optname, optname);
> usage();
> }
>
> - if (stat64(name, &statbuf)) {
> + if (statres) {
> if (errno == ENOENT && *isfile) {
> if (create)
> *create = 1;
> @@ -1059,9 +1063,9 @@ check_device_type(
> }
>
> /*
> - * We only want to completely truncate and recreate an existing file if
> - * we were specifically told it was a file. Set the create flag only in
> - * this case to trigger that behaviour.
> + * We only want to create a file only if we were specifically told
> + * we want a file. Set the create flag only in this case to trigger
> + * that behaviour.

+ * We only want to create a file if we were specifically told it is a
+ * file. Set the create flag only in this case to trigger that behaviour.

> */
> if (S_ISREG(statbuf.st_mode)) {
> if (!*isfile)