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| author | Rich Felker <dalias@libc.org> | 2020-08-31 18:32:08 +0300 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2024-01-22 17:33:37 +0300 |
| commit | 73fa7547c70b32cc69685f79be31135797734eb6 (patch) | |
| tree | 61eca04ae3dafb7132f40baa1e73b27dd9f3f949 /include/uapi/linux/fs.h | |
| parent | 9e3f1c59367515e7e40675fe83645a131c05039d (diff) | |
| download | linux-73fa7547c70b32cc69685f79be31135797734eb6.tar.xz | |
vfs: add RWF_NOAPPEND flag for pwritev2
The pwrite function, originally defined by POSIX (thus the "p"), is
defined to ignore O_APPEND and write at the offset passed as its
argument. However, historically Linux honored O_APPEND if set and
ignored the offset. This cannot be changed due to stability policy,
but is documented in the man page as a bug.
Now that there's a pwritev2 syscall providing a superset of the pwrite
functionality that has a flags argument, the conforming behavior can
be offered to userspace via a new flag. Since pwritev2 checks flag
validity (in kiocb_set_rw_flags) and reports unknown ones with
EOPNOTSUPP, callers will not get wrong behavior on old kernels that
don't support the new flag; the error is reported and the caller can
decide how to handle it.
Signed-off-by: Rich Felker <dalias@libc.org>
Link: https://lore.kernel.org/r/20200831153207.GO3265@brightrain.aerifal.cx
Reviewed-by: Jann Horn <jannh@google.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'include/uapi/linux/fs.h')
| -rw-r--r-- | include/uapi/linux/fs.h | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index 48ad69f7722e..2203d3194b91 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -301,9 +301,12 @@ typedef int __bitwise __kernel_rwf_t; /* per-IO O_APPEND */ #define RWF_APPEND ((__force __kernel_rwf_t)0x00000010) +/* per-IO negation of O_APPEND */ +#define RWF_NOAPPEND ((__force __kernel_rwf_t)0x00000020) + /* mask of flags supported by the kernel */ #define RWF_SUPPORTED (RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT |\ - RWF_APPEND) + RWF_APPEND | RWF_NOAPPEND) /* Pagemap ioctl */ #define PAGEMAP_SCAN _IOWR('f', 16, struct pm_scan_arg) |