Hello Simone,
On 8/18/19 4:48 PM, Simone Piccardi wrote:
Hi,
I was looking at version from 2017-09-15 but it's the same on:
http://man7.org/linux/man-pages/man2/statx.2.html (2019-03-06)
There is reported (about the mask argument) after the list of constats:
> Note that the kernel does not reject values in mask other than the
> above. Instead, it simply informs the caller which values are sup‐
> ported by this kernel and filesystem via the statx.stx_mask field.
But as reported in the error values, there can be EINVAL if mask has a
reserved valued, and I found a check against STATX__RESERVED in
fs/stat.c for this. So if you use a that bit (0x80000000U) the kernel
will reject the value.
Probably is better to say that the kernel do not enforce the use of only
the listed values, but there are anyway reserved values so and so you
cannot put whatever you want on mask (that apply to more values than
UINT_MAX).
Thanks for the report. I applied the patch below.
Cheers,
Michael
diff --git a/man2/statx.2 b/man2/statx.2
index 49d48daaa..2370aa1d9 100644
--- a/man2/statx.2
+++ b/man2/statx.2
@@ -265,11 +265,14 @@ STATX_ALL [All currently available fields]
.TE
.in
.PP
-Note that the kernel does
+Note that, in general, the kernel does
.I not
reject values in
.I mask
other than the above.
+(For an exception, see
+.B EINVAL
+in errors.)
Instead, it simply informs the caller which values are supported
by this kernel and filesystem via the
.I statx.stx_mask
@@ -490,6 +493,9 @@ Invalid flag specified in
.B EINVAL
Reserved flag specified in
.IR mask .
+(Currently, there is one such flag, designated by the constant
+.BR STATX__RESERVED ,
+with the value 0x80000000U.)
.TP
.B ELOOP
Too many symbolic links encountered while traversing the pathname.
