The patch titled
Subject: tmpfs: support 64-bit inums per-sb fix
has been added to the -mm tree. Its filename is
tmpfs-support-64-bit-inums-per-sb-fix.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/tmpfs-support-64-bit-inums-per-sb-fix.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/tmpfs-support-64-bit-inums-per-sb-fix.patch
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------------------------------------------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: tmpfs: support 64-bit inums per-sb fix
Expanded Chris's Documentation and Kconfig help on tmpfs inode64.
TMPFS_INODE64 still there, still default N, but writing down its very
limited limitation does make me wonder again if we want the option.
Link: http://lkml.kernel.org/r/alpine.LSU.2.11.2008011928010.13320@eggly.anvils
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Amir Goldstein <amir73il@xxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Jeff Layton <jlayton@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/filesystems/tmpfs.rst | 13 ++++++++++---
fs/Kconfig | 16 +++++++++++-----
2 files changed, 21 insertions(+), 8 deletions(-)
--- a/Documentation/filesystems/tmpfs.rst~tmpfs-support-64-bit-inums-per-sb-fix
+++ a/Documentation/filesystems/tmpfs.rst
@@ -153,11 +153,18 @@ parameters with chmod(1), chown(1) and c
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.
-On 64-bit, the default is set by CONFIG_TMPFS_INODE64. On 32-bit, inode64 is
-not legal and will produce an error at mount time.
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
@@ -170,5 +177,5 @@ RAM/SWAP in 10240 inodes and it is only
Hugh Dickins, 4 June 2007
:Updated:
KOSAKI Motohiro, 16 Mar 2010
-Updated:
+:Updated:
Chris Down, 13 July 2020
--- a/fs/Kconfig~tmpfs-support-64-bit-inums-per-sb-fix
+++ a/fs/Kconfig
@@ -207,12 +207,18 @@ config TMPFS_INODE64
default n
help
tmpfs has historically used only inode numbers as wide as an unsigned
- int. In some cases this can cause wraparound, potentially resulting in
- multiple files with the same inode number on a single device. This option
- makes tmpfs use the full width of ino_t by default, similarly to the
- inode64 mount option.
+ int. In some cases this can cause wraparound, potentially resulting
+ in multiple files with the same inode number on a single device. This
+ option makes tmpfs use the full width of ino_t by default, without
+ needing to specify the inode64 option when mounting.
- To override this default, use the inode32 or inode64 mount options.
+ But if a long-lived tmpfs is to be accessed by 32-bit applications so
+ ancient that opening a file larger than 2GiB fails with EINVAL, then
+ the INODE64 config option and inode64 mount option risk operations
+ failing with EOVERFLOW once 33-bit inode numbers are reached.
+
+ To override this configured default, use the inode32 or inode64
+ option when mounting.
If unsure, say N.
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
tmpfs-support-64-bit-inums-per-sb-fix.patch
mm-memcontrol-decouple-reference-counting-from-page-accounting-fix.patch
khugepaged-collapse_pte_mapped_thp-flush-the-right-range.patch
khugepaged-collapse_pte_mapped_thp-protect-the-pmd-lock.patch
khugepaged-retract_page_tables-remember-to-test-exit.patch
khugepaged-khugepaged_test_exit-check-mmget_still_valid.patch
