[v5,2/2] tmpfs: Support 64-bit inums per-sb

Message ID	ae9306ab10ce3d794c13b1836f5473e89562b98c.1578225806.git.chris@chrisdown.name (mailing list archive)
State	New, archived
Headers	show Return-Path: <SRS0=YM2v=22=kvack.org=owner-linux-mm@kernel.org> DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B492E24650 Date: Sun, 5 Jan 2020 12:06:05 +0000 From: Chris Down <chris@chrisdown.name> To: linux-mm@kvack.org Cc: Hugh Dickins <hughd@google.com>, Andrew Morton <akpm@linux-foundation.org>, Al Viro <viro@zeniv.linux.org.uk>, Matthew Wilcox <willy@infradead.org>, Amir Goldstein <amir73il@gmail.com>, Jeff Layton <jlayton@kernel.org>, Johannes Weiner <hannes@cmpxchg.org>, Tejun Heo <tj@kernel.org>, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: [PATCH v5 2/2] tmpfs: Support 64-bit inums per-sb Message-ID: <ae9306ab10ce3d794c13b1836f5473e89562b98c.1578225806.git.chris@chrisdown.name> References: <cover.1578225806.git.chris@chrisdown.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <cover.1578225806.git.chris@chrisdown.name> Sender: owner-linux-mm@kvack.org Precedence: bulk
Series	fs: inode: shmem: Reduce risk of inum overflow \| expand [v5,0/2] fs: inode: shmem: Reduce risk of inum overflow [v5,1/2] tmpfs: Add per-superblock i_ino support [v5,2/2] tmpfs: Support 64-bit inums per-sb

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..e74f127df22a 100644 --- a/fs/Kconfig +++ b/fs/Kconfig @@ -199,6 +199,21 @@ 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. + + 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 7fac91f490dc..8925eb774518 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 next_ino; /* The next per-sb inode number to use */ 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 9e97ba972225..05de65112bed 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 @@ -2261,15 +2263,24 @@ 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(); } else { spin_lock(&sbinfo->stat_lock); - if (unlikely(sbinfo->next_ino > UINT_MAX)) { + if (unlikely(!sbinfo->full_inums && + sbinfo->next_ino > UINT_MAX)) { /* * Emulate get_next_ino uint wraparound for * compatibility */ + pr_warn("%s: inode number overflow on device %d, consider using inode64 mount option\n", + __func__, MINOR(sb->s_dev)); sbinfo->next_ino = 1; } inode->i_ino = sbinfo->next_ino++; @@ -3406,6 +3417,8 @@ enum shmem_param { Opt_nr_inodes, Opt_size, Opt_uid, + Opt_inode32, + Opt_inode64, }; static const struct fs_parameter_spec shmem_param_specs[] = { @@ -3417,6 +3430,8 @@ static const struct fs_parameter_spec shmem_param_specs[] = { fsparam_string("nr_inodes", Opt_nr_inodes), fsparam_string("size", Opt_size), fsparam_u32 ("uid", Opt_uid), + fsparam_flag ("inode32", Opt_inode32), + fsparam_flag ("inode64", Opt_inode64), {} }; @@ -3441,6 +3456,7 @@ 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) @@ -3502,6 +3518,18 @@ 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; @@ -3509,6 +3537,8 @@ 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) @@ -3593,8 +3623,16 @@ static int shmem_reconfigure(struct fs_context *fc) } } + if ((ctx->seen & SHMEM_SEEN_INUMS) && !ctx->full_inums && + sbinfo->next_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_INUMS) + sbinfo->full_inums = ctx->full_inums; if (ctx->seen & SHMEM_SEEN_BLOCKS) sbinfo->max_blocks = ctx->blocks; if (ctx->seen & SHMEM_SEEN_INODES) { @@ -3634,6 +3672,29 @@ 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) @@ -3681,6 +3742,8 @@ static int shmem_fill_super(struct super_block *sb, struct fs_context *fc) ctx->blocks = shmem_default_max_blocks(); if (!(ctx->seen & SHMEM_SEEN_INODES)) ctx->inodes = shmem_default_max_inodes(); + if (!(ctx->seen & SHMEM_SEEN_INUMS)) + ctx->full_inums = IS_ENABLED(CONFIG_TMPFS_INODE64); } else { sb->s_flags |= SB_NOUSER; } @@ -3694,6 +3757,7 @@ 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;

[v5,2/2] tmpfs: Support 64-bit inums per-sb

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