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authorChris Down <chris@chrisdown.name>2020-08-06 23:20:25 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-08-07 11:33:24 -0700
commitea3271f7196c65ae5d3e1c7b3f733892c017dbd6 (patch)
treeb8e35df0da0afea4a25cfdaf2ceaf07d7db30f62 /Documentation/filesystems
parente809d5f0b5c912fe981dce738f3283b2010665f0 (diff)
tmpfs: support 64-bit inums per-sb
The default is still set to inode32 for backwards compatibility, but system administrators can opt in to the new 64-bit inode numbers by either: 1. Passing inode64 on the command line when mounting, or 2. Configuring the kernel with CONFIG_TMPFS_INODE64=y The inode64 and inode32 names are used based on existing precedent from XFS. [hughd@google.com: Kconfig fixes] Link: http://lkml.kernel.org/r/alpine.LSU.2.11.2008011928010.13320@eggly.anvils Signed-off-by: Chris Down <chris@chrisdown.name> Signed-off-by: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Acked-by: Hugh Dickins <hughd@google.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Matthew Wilcox <willy@infradead.org> Cc: Jeff Layton <jlayton@kernel.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Tejun Heo <tj@kernel.org> Link: http://lkml.kernel.org/r/8b23758d0c66b5e2263e08baf9c4b6a7565cbd8f.1594661218.git.chris@chrisdown.name Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/filesystems')
-rw-r--r--Documentation/filesystems/tmpfs.rst18
1 files changed, 18 insertions, 0 deletions
diff --git a/Documentation/filesystems/tmpfs.rst b/Documentation/filesystems/tmpfs.rst
index 4e95929301a5..c44f8b1d3cab 100644
--- a/Documentation/filesystems/tmpfs.rst
+++ b/Documentation/filesystems/tmpfs.rst
@@ -150,6 +150,22 @@ These options do not have any effect on remount. You can change these
parameters with chmod(1), chown(1) and chgrp(1) on a mounted filesystem.
+tmpfs has a mount option to select whether it will wrap at 32- or 64-bit inode
+numbers:
+
+======= ========================
+inode64 Use 64-bit inode numbers
+inode32 Use 32-bit inode numbers
+======= ========================
+
+On a 32-bit kernel, inode32 is implicit, and inode64 is refused at mount time.
+On a 64-bit kernel, CONFIG_TMPFS_INODE64 sets the default. inode64 avoids the
+possibility of multiple files with the same inode number on a single device;
+but risks glibc failing with EOVERFLOW once 33-bit inode numbers are reached -
+if a long-lived tmpfs is accessed by 32-bit applications so ancient that
+opening a file larger than 2GiB fails with EINVAL.
+
+
So 'mount -t tmpfs -o size=10G,nr_inodes=10k,mode=700 tmpfs /mytmpfs'
will give you tmpfs instance on /mytmpfs which can allocate 10GB
RAM/SWAP in 10240 inodes and it is only accessible by root.
@@ -161,3 +177,5 @@ RAM/SWAP in 10240 inodes and it is only accessible by root.
Hugh Dickins, 4 June 2007
:Updated:
KOSAKI Motohiro, 16 Mar 2010
+:Updated:
+ Chris Down, 13 July 2020