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fs: add RWF_APPEND 

This is the per-I/O equivalent of O_APPEND to support atomic append
operations on any open file.

If a file is opened with O_APPEND, pwrite() ignores the offset and
always appends data to the end of the file. RWF_APPEND enables atomic
append and pwrite() with offset on a single file descriptor.

Signed-off-by: Jürg Billeter <j@bitron.ch>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Jürg Billeter 2017-09-29 14:07:17 +02:00 committed by Al Viro
parent c981f254cc
commit e1fc742e14
2 changed files with 7 additions and 1 deletions
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2
include/linux/fs.h
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@ -3224,6 +3224,8 @@ static inline int kiocb_set_rw_flags(struct kiocb *ki, rwf_t flags)
ki->ki_flags |= IOCB_DSYNC;
if (flags & RWF_SYNC)
ki->ki_flags |= (IOCB_DSYNC | IOCB_SYNC);
if (flags & RWF_APPEND)
ki->ki_flags |= IOCB_APPEND;
return 0;
}

6
include/uapi/linux/fs.h
View File

@ -377,7 +377,11 @@ typedef int __bitwise __kernel_rwf_t;
/* per-IO, return -EAGAIN if operation would block */
#define RWF_NOWAIT ((__force __kernel_rwf_t)0x00000008)
/* per-IO O_APPEND */
#define RWF_APPEND ((__force __kernel_rwf_t)0x00000010)
/* mask of flags supported by the kernel */
#define RWF_SUPPORTED (RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT)
#define RWF_SUPPORTED (RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT |\
RWF_APPEND)
#endif /* _UAPI_LINUX_FS_H */