user_namespaces.7: Restore historical details about UID maps

Christian Brauner's patch added the Linux 4.15 details,
but we need to retain the historical details.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

diff --git a/man7/user_namespaces.7 b/man7/user_namespaces.7
index 5968c09ccc96323a792141851e6b3560e1834f15..2fe00fb40b48c3d17b454f02943ef2d733acfbc9 100644 (file)
--- a/man7/user_namespaces.7
+++ b/man7/user_namespaces.7
@@ -511,7 +511,12 @@ and the last field must be greater than 0.
 Lines are terminated by newline characters.
 .IP *
 There is a limit on the number of lines in the file.
-As of Linux 4.15, the limit is 340 lines.
+In Linux 4.14 and earlier, this limit was (arbitrarily)
+.\" 5*12-byte records could fit in a 64B cache line
+set at 5 lines.
+Since Linux 4.15,
+.\" commit 6397fac4915ab3002dc15aae751455da1a852f25
+the limit is 340 lines.
 In addition, the number of bytes written to
 the file must be less than the system page size,
 and the write must be performed at the start of the file (i.e.,