Commit e07c469e authored by Hugh Dickins's avatar Hugh Dickins Committed by Christian Brauner
Browse files

tmpfs: track free_ispace instead of free_inodes 



In preparation for assigning some inode space to extended attributes,
keep track of free_ispace instead of number of free_inodes: as if one
tmpfs inode (and accompanying dentry) occupies very approximately 1KiB.

Unsigned long is large enough for free_ispace, on 64-bit and on 32-bit:
but take care to enforce the maximum.  And fix the nr_blocks maximum on
32-bit: S64_MAX would be too big for it there, so say LONG_MAX instead.

Delete the incorrect limited<->unlimited blocks/inodes comment above
shmem_reconfigure(): leave it to the error messages below to describe.

Signed-off-by: default avatarHugh Dickins <hughd@google.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Reviewed-by: default avatarCarlos Maiolino <cmaiolino@redhat.com>
Message-Id: <4fe1739-d9e7-8dfd-5bce-12e7339711da@google.com>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 5de75970

include/linux/shmem_fs.h

+1 −1
Original line number Diff line number Diff line
@@ -54,7 +54,7 @@ struct shmem_sb_info { 
	unsigned long max_blocks;   /* How many blocks are allowed */

	struct percpu_counter used_blocks;  /* How many are allocated */

	unsigned long max_inodes;   /* How many inodes are allowed */

	unsigned long free_inodes;  /* How many are left for allocation */

	unsigned long free_ispace;  /* How much ispace left for allocation */

	raw_spinlock_t stat_lock;   /* Serialize shmem_sb_info changes */

	umode_t mode;		    /* Mount mode for root directory */

	unsigned char huge;	    /* Whether to try for hugepages */

mm/shmem.c

+17 −16
Original line number Diff line number Diff line
@@ -90,6 +90,9 @@ static struct vfsmount *shm_mnt; 
/* Pretend that each entry is of this size in directory's i_size */

#define BOGO_DIRENT_SIZE 20



/* Pretend that one inode + its dentry occupy this much memory */

#define BOGO_INODE_SIZE 1024



/* Symlink up to this size is kmalloc'ed instead of using a swappable page */

#define SHORT_SYMLINK_LEN 128
@@ -137,7 +140,8 @@ static unsigned long shmem_default_max_inodes(void) 
{

	unsigned long nr_pages = totalram_pages();



	return min(nr_pages - totalhigh_pages(), nr_pages / 2);

	return min3(nr_pages - totalhigh_pages(), nr_pages / 2,

			ULONG_MAX / BOGO_INODE_SIZE);

}

#endif
@@ -331,11 +335,11 @@ static int shmem_reserve_inode(struct super_block *sb, ino_t *inop) 
	if (!(sb->s_flags & SB_KERNMOUNT)) {

		raw_spin_lock(&sbinfo->stat_lock);

		if (sbinfo->max_inodes) {

			if (!sbinfo->free_inodes) {

			if (sbinfo->free_ispace < BOGO_INODE_SIZE) {

				raw_spin_unlock(&sbinfo->stat_lock);

				return -ENOSPC;

			}

			sbinfo->free_inodes--;

			sbinfo->free_ispace -= BOGO_INODE_SIZE;

		}

		if (inop) {

			ino = sbinfo->next_ino++;
@@ -394,7 +398,7 @@ static void shmem_free_inode(struct super_block *sb) 
	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);

	if (sbinfo->max_inodes) {

		raw_spin_lock(&sbinfo->stat_lock);

		sbinfo->free_inodes++;

		sbinfo->free_ispace += BOGO_INODE_SIZE;

		raw_spin_unlock(&sbinfo->stat_lock);

	}

}
@@ -3158,7 +3162,7 @@ static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf) 
	}

	if (sbinfo->max_inodes) {

		buf->f_files = sbinfo->max_inodes;

		buf->f_ffree = sbinfo->free_inodes;

		buf->f_ffree = sbinfo->free_ispace / BOGO_INODE_SIZE;

	}

	/* else leave those fields 0 like simple_statfs */
@@ -3818,13 +3822,13 @@ static int shmem_parse_one(struct fs_context *fc, struct fs_parameter *param) 
		break;

	case Opt_nr_blocks:

		ctx->blocks = memparse(param->string, &rest);

		if (*rest || ctx->blocks > S64_MAX)

		if (*rest || ctx->blocks > LONG_MAX)

			goto bad_value;

		ctx->seen |= SHMEM_SEEN_BLOCKS;

		break;

	case Opt_nr_inodes:

		ctx->inodes = memparse(param->string, &rest);

		if (*rest)

		if (*rest || ctx->inodes > ULONG_MAX / BOGO_INODE_SIZE)

			goto bad_value;

		ctx->seen |= SHMEM_SEEN_INODES;

		break;
@@ -4005,21 +4009,17 @@ static int shmem_parse_options(struct fs_context *fc, void *data) 


/*

 * Reconfigure a shmem filesystem.

 *

 * Note that we disallow change from limited->unlimited blocks/inodes while any

 * are in use; but we must separately disallow unlimited->limited, because in

 * that case we have no record of how much is already in use.

 */

static int shmem_reconfigure(struct fs_context *fc)

{

	struct shmem_options *ctx = fc->fs_private;

	struct shmem_sb_info *sbinfo = SHMEM_SB(fc->root->d_sb);

	unsigned long inodes;

	unsigned long used_isp;

	struct mempolicy *mpol = NULL;

	const char *err;



	raw_spin_lock(&sbinfo->stat_lock);

	inodes = sbinfo->max_inodes - sbinfo->free_inodes;

	used_isp = sbinfo->max_inodes * BOGO_INODE_SIZE - sbinfo->free_ispace;



	if ((ctx->seen & SHMEM_SEEN_BLOCKS) && ctx->blocks) {

		if (!sbinfo->max_blocks) {
@@ -4037,7 +4037,7 @@ static int shmem_reconfigure(struct fs_context *fc) 
			err = "Cannot retroactively limit inodes";

			goto out;

		}

		if (ctx->inodes < inodes) {

		if (ctx->inodes * BOGO_INODE_SIZE < used_isp) {

			err = "Too few inodes for current use";

			goto out;

		}
@@ -4083,7 +4083,7 @@ static int shmem_reconfigure(struct fs_context *fc) 
		sbinfo->max_blocks  = ctx->blocks;

	if (ctx->seen & SHMEM_SEEN_INODES) {

		sbinfo->max_inodes  = ctx->inodes;

		sbinfo->free_inodes = ctx->inodes - inodes;

		sbinfo->free_ispace = ctx->inodes * BOGO_INODE_SIZE - used_isp;

	}



	/*
@@ -4214,7 +4214,8 @@ static int shmem_fill_super(struct super_block *sb, struct fs_context *fc) 
	sb->s_flags |= SB_NOUSER;

#endif

	sbinfo->max_blocks = ctx->blocks;

	sbinfo->free_inodes = sbinfo->max_inodes = ctx->inodes;

	sbinfo->max_inodes = ctx->inodes;

	sbinfo->free_ispace = sbinfo->max_inodes * BOGO_INODE_SIZE;

	if (sb->s_flags & SB_KERNMOUNT) {

		sbinfo->ino_batch = alloc_percpu(ino_t);

		if (!sbinfo->ino_batch)