io_uring: allow use of offset == -1 to mean file position

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This behaves like preadv2/pwritev2 with offset == -1, it'll use (and
update) the current file position. This obviously comes with the caveat
that if the application has multiple read/writes in flight, then the
end result will not be as expected. This is similar to threads sharing
a file descriptor and doing IO using the current file position.

Since this feature isn't easily detectable by doing a read or write,
add a feature flags, IORING_FEAT_RW_CUR_POS, to allow applications to
detect presence of this feature.

Reported-by: 李通洲 <carter.li@eoitek.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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This commit is contained in:

Jens Axboe 2019-12-25 16:33:42 -07:00

parent 3a6820f2bb

commit ba04291eb6

2 changed files with 11 additions and 1 deletions

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11

fs/io_uring.c

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1

include/uapi/linux/io_uring.h

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