[PATCH liburing v2] man/io_uring_enter.2: update notes about direct open/accept

[Pavel Begunkov <asml.silence@gmail.com>]

Reflect recent changes in the man, i.e. direct open/accept now would try
to remove a file from the fixed file table if the slot they target is
already taken.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---

v2: note about replacing existing files

 man/io_uring_enter.2 | 30 ++++++++++++++++++------------
 1 file changed, 18 insertions(+), 12 deletions(-)

diff --git a/man/io_uring_enter.2 b/man/io_uring_enter.2
index ad86961..6b31061 100644
--- a/man/io_uring_enter.2
+++ b/man/io_uring_enter.2
@@ -517,10 +517,12 @@ field is set to a positive number, the file won't be installed into the
 normal file table as usual but will be placed into the fixed file table at index
 .I file_index - 1.
 In this case, instead of returning a file descriptor, the result will contain
-either 0 on success or an error. If there is already a file registered at this
-index, the request will fail with
-.B -EBADF.
-Only io_uring has access to such files and no other syscall can use them. See
+either 0 on success or an error. If the index points to a valid empty slot, the
+installation is guaranteed to not fail. If there is already a file in the slot,
+it will be replaced, similar to
+.B IORING_OP_FILES_UPDATE.
+Please note that only io_uring has access to such files and no other syscall
+can use them. See
 .B IOSQE_FIXED_FILE
 and
 .B IORING_REGISTER_FILES.
@@ -656,10 +658,12 @@ field is set to a positive number, the file won't be installed into the
 normal file table as usual but will be placed into the fixed file table at index
 .I file_index - 1.
 In this case, instead of returning a file descriptor, the result will contain
-either 0 on success or an error. If there is already a file registered at this
-index, the request will fail with
-.B -EBADF.
-Only io_uring has access to such files and no other syscall can use them. See
+either 0 on success or an error. If the index points to a valid empty slot, the
+installation is guaranteed to not fail. If there is already a file in the slot,
+it will be replaced, similar to
+.B IORING_OP_FILES_UPDATE.
+Please note that only io_uring has access to such files and no other syscall
+can use them. See
 .B IOSQE_FIXED_FILE
 and
 .B IORING_REGISTER_FILES.
@@ -692,10 +696,12 @@ field is set to a positive number, the file won't be installed into the
 normal file table as usual but will be placed into the fixed file table at index
 .I file_index - 1.
 In this case, instead of returning a file descriptor, the result will contain
-either 0 on success or an error. If there is already a file registered at this
-index, the request will fail with
-.B -EBADF.
-Only io_uring has access to such files and no other syscall can use them. See
+either 0 on success or an error. If the index points to a valid empty slot, the
+installation is guaranteed to not fail. If there is already a file in the slot,
+it will be replaced, similar to
+.B IORING_OP_FILES_UPDATE.
+Please note that only io_uring has access to such files and no other syscall
+can use them. See
 .B IOSQE_FIXED_FILE
 and
 .B IORING_REGISTER_FILES.
-- 
2.33.0