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| author | Michael Kerrisk <mtk.manpages@gmail.com> | 2020-02-08 14:10:31 +0100 |
|---|---|---|
| committer | Michael Kerrisk <mtk.manpages@gmail.com> | 2020-02-08 14:10:31 +0100 |
| commit | f3aa51b217ff28380edae560c7129d3b7262ce36 (patch) | |
| tree | e9400d7710eec4e891aaaa1c5a513116058202bc | |
| parent | e15b10ba32414c50478bf6f4efec7537485e5196 (diff) | |
| download | man-pages-f3aa51b217ff28380edae560c7129d3b7262ce36.tar.gz | |
fcntl.2: Further tweaks to F_SEAL_FUTURE_WRITE text
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
| -rw-r--r-- | man2/fcntl.2 | 14 |
1 files changed, 8 insertions, 6 deletions
diff --git a/man2/fcntl.2 b/man2/fcntl.2 index cb4445bb45..e74950cda7 100644 --- a/man2/fcntl.2 +++ b/man2/fcntl.2 @@ -1527,8 +1527,10 @@ pending on the file, all outstanding writes will be discarded. .TP .BR F_SEAL_FUTURE_WRITE " (since Linux 5.1)" -If this seal is set, the contents of the file can be modified only from -existing writable mappings that were created prior to the seal being set. +The effect of this seal is similar to +.BR F_SEAL_WRITE , +but the contents of the file can still be modified via +shared writable mappings that were created prior to the seal being set. Any attempt to create a new writable mapping on the file via .BR mmap (2) will fail with @@ -1537,10 +1539,10 @@ Likewise, an attempt to write to the file via .BR write (2) will fail with .BR EPERM . -This is useful in situations where existing writable mapped -regions need to be kept intact while preventing any future writes. -For example, to share a -read-only memory buffer to other processes that only the sender can write to. +.IP +Using this seal, +one process can create a memory buffer that it can continue to modify +while sharing that buffer on a "read-only" basis with other processes. .\" .SS File read/write hints Write lifetime hints can be used to inform the kernel about the relative |