[PATCH v2 2/2] tmpfs: Support 64-bit inums per-sb

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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

Signed-off-by: Chris Down <chris@xxxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Amir Goldstein <amir73il@xxxxxxxxx>
Cc: Jeff Layton <jlayton@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: kernel-team@xxxxxx
---
 Documentation/filesystems/tmpfs.txt | 11 ++++++
 fs/Kconfig                          | 18 +++++++++
 include/linux/shmem_fs.h            |  1 +
 mm/shmem.c                          | 57 ++++++++++++++++++++++++++++-
 4 files changed, 86 insertions(+), 1 deletion(-)

diff --git a/Documentation/filesystems/tmpfs.txt b/Documentation/filesystems/tmpfs.txt
index 5ecbc03e6b2f..203e12a684c9 100644
--- a/Documentation/filesystems/tmpfs.txt
+++ b/Documentation/filesystems/tmpfs.txt
@@ -136,6 +136,15 @@ 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 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
 RAM/SWAP in 10240 inodes and it is only accessible by root.
@@ -147,3 +156,5 @@ Updated:
    Hugh Dickins, 4 June 2007
 Updated:
    KOSAKI Motohiro, 16 Mar 2010
+Updated:
+   Chris Down, 2 Jan 2020
diff --git a/fs/Kconfig b/fs/Kconfig
index 7b623e9fc1b0..af2048ae71eb 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -199,6 +199,24 @@ config TMPFS_XATTR
 
 	  If unsure, say N.
 
+config TMPFS_INODE64
+	bool "Use 64-bit ino_t by default in tmpfs"
+	depends on TMPFS && 64BIT
+	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.
+
+	  tmpfs mounts that are used privately by the kernel and are not visible to
+	  users are unaffected.
+
+	  To override this default, use the inode32 or inode64 mount options.
+
+	  If unsure, say N.
+
 config HUGETLBFS
 	bool "HugeTLB file system support"
 	depends on X86 || IA64 || SPARC64 || (S390 && 64BIT) || \
diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index dec4353cf3b7..0e645ecd6451 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -35,6 +35,7 @@ struct shmem_sb_info {
 	unsigned char huge;	    /* Whether to try for hugepages */
 	kuid_t uid;		    /* Mount uid for root directory */
 	kgid_t gid;		    /* Mount gid for root directory */
+	bool full_inums;	    /* If i_ino should be uint or ino_t */
 	ino_t last_ino;		    /* The last used per-sb inode number */
 	struct mempolicy *mpol;     /* default memory policy for mappings */
 	spinlock_t shrinklist_lock;   /* Protects shrinklist */
diff --git a/mm/shmem.c b/mm/shmem.c
index 8af9fb922a96..fd2542e5ada9 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -115,11 +115,13 @@ struct shmem_options {
 	kuid_t uid;
 	kgid_t gid;
 	umode_t mode;
+	bool full_inums;
 	int huge;
 	int seen;
 #define SHMEM_SEEN_BLOCKS 1
 #define SHMEM_SEEN_INODES 2
 #define SHMEM_SEEN_HUGE 4
+#define SHMEM_SEEN_INUMS 8
 };
 
 #ifdef CONFIG_TMPFS
@@ -2260,7 +2262,8 @@ static struct inode *shmem_get_inode(struct super_block *sb, const struct inode
 		if (use_sb_ino) {
 			spin_lock(&sbinfo->stat_lock);
 			inode->i_ino = sbinfo->last_ino++;
-			if (unlikely(inode->i_ino >= UINT_MAX)) {
+			if (unlikely(!sbinfo->full_inums &&
+				     inode->i_ino >= UINT_MAX)) {
 				/*
 				 * Emulate get_next_ino uint wraparound for
 				 * compatibility
@@ -2277,6 +2280,12 @@ static struct inode *shmem_get_inode(struct super_block *sb, const struct inode
 			 * since max_inodes is always 0, and is called from
 			 * potentially unknown contexts. As such, use the global
 			 * allocator which doesn't require the per-sb stat_lock.
+			 *
+			 * No special behaviour is needed for
+			 * sbinfo->full_inums, because it's not possible to
+			 * manually set on callers of this type, and
+			 * CONFIG_TMPFS_INODE64 only applies to user-visible
+			 * mounts.
 			 */
 			inode->i_ino = get_next_ino();
 		}
@@ -3450,6 +3459,7 @@ static int shmem_parse_one(struct fs_context *fc, struct fs_parameter *param)
 	unsigned long long size;
 	char *rest;
 	int opt;
+	const char *err;
 
 	opt = fs_parse(fc, &shmem_fs_parameters, param, &result);
 	if (opt < 0)
@@ -3511,6 +3521,18 @@ static int shmem_parse_one(struct fs_context *fc, struct fs_parameter *param)
 			break;
 		}
 		goto unsupported_parameter;
+	case Opt_inode32:
+		ctx->full_inums = false;
+		ctx->seen |= SHMEM_SEEN_INUMS;
+		break;
+	case Opt_inode64:
+		if (sizeof(ino_t) < 8) {
+			err = "Cannot use inode64 with <64bit inums in kernel";
+			goto err_msg;
+		}
+		ctx->full_inums = true;
+		ctx->seen |= SHMEM_SEEN_INUMS;
+		break;
 	}
 	return 0;
 
@@ -3518,6 +3540,8 @@ static int shmem_parse_one(struct fs_context *fc, struct fs_parameter *param)
 	return invalf(fc, "tmpfs: Unsupported parameter '%s'", param->key);
 bad_value:
 	return invalf(fc, "tmpfs: Bad value for '%s'", param->key);
+err_msg:
+	return invalf(fc, "tmpfs: %s", err);
 }
 
 static int shmem_parse_options(struct fs_context *fc, void *data)
@@ -3602,6 +3626,12 @@ static int shmem_reconfigure(struct fs_context *fc)
 		}
 	}
 
+	if ((ctx->seen & SHMEM_SEEN_INUMS) && !ctx->full_inums &&
+	    sbinfo->last_ino > UINT_MAX) {
+		err = "Current inum too high to switch to 32-bit inums";
+		goto out;
+	}
+
 	if (ctx->seen & SHMEM_SEEN_HUGE)
 		sbinfo->huge = ctx->huge;
 	if (ctx->seen & SHMEM_SEEN_BLOCKS)
@@ -3643,6 +3673,29 @@ static int shmem_show_options(struct seq_file *seq, struct dentry *root)
 	if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
 		seq_printf(seq, ",gid=%u",
 				from_kgid_munged(&init_user_ns, sbinfo->gid));
+
+	/*
+	 * Showing inode{64,32} might be useful even if it's the system default,
+	 * since then people don't have to resort to checking both here and
+	 * /proc/config.gz to confirm 64-bit inums were successfully applied
+	 * (which may not even exist if IKCONFIG_PROC isn't enabled).
+	 *
+	 * We hide it when inode64 isn't the default and we are using 32-bit
+	 * inodes, since that probably just means the feature isn't even under
+	 * consideration.
+	 *
+	 * As such:
+	 *
+	 *                     +-----------------+-----------------+
+	 *                     | TMPFS_INODE64=y | TMPFS_INODE64=n |
+	 *  +------------------+-----------------+-----------------+
+	 *  | full_inums=true  | show            | show            |
+	 *  | full_inums=false | show            | hide            |
+	 *  +------------------+-----------------+-----------------+
+	 *
+	 */
+	if (IS_ENABLED(CONFIG_TMPFS_INODE64) || !sbinfo->full_inums)
+		seq_printf(seq, ",inode%d", (sbinfo->full_inums ? 64 : 32));
 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
 	/* Rightly or wrongly, show huge mount option unmasked by shmem_huge */
 	if (sbinfo->huge)
@@ -3702,6 +3755,7 @@ static int shmem_fill_super(struct super_block *sb, struct fs_context *fc)
 	sbinfo->free_inodes = sbinfo->max_inodes = ctx->inodes;
 	sbinfo->uid = ctx->uid;
 	sbinfo->gid = ctx->gid;
+	sbinfo->full_inums = ctx->full_inums;
 	sbinfo->mode = ctx->mode;
 	sbinfo->huge = ctx->huge;
 	sbinfo->mpol = ctx->mpol;
@@ -3915,6 +3969,7 @@ int shmem_init_fs_context(struct fs_context *fc)
 	ctx->mode = 0777 | S_ISVTX;
 	ctx->uid = current_fsuid();
 	ctx->gid = current_fsgid();
+	ctx->full_inums = IS_ENABLED(CONFIG_TMPFS_INODE64);
 
 	fc->fs_private = ctx;
 	fc->ops = &shmem_fs_context_ops;
-- 
2.24.1




[Index of Archives]     [Linux Ext4 Filesystem]     [Union Filesystem]     [Filesystem Testing]     [Ceph Users]     [Ecryptfs]     [AutoFS]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux Cachefs]     [Reiser Filesystem]     [Linux RAID]     [Samba]     [Device Mapper]     [CEPH Development]

  Powered by Linux