[RFC 8/8] shmem: add support to customize block size on multiple PAGE_SIZE
From: Luis Chamberlain
Date: Fri Apr 21 2023 - 17:44:49 EST
This allows tmpfs mounts to use a custom block size. We only allow
block sizes greater than PAGE_SIZE, and these must also be a multiple
of the PAGE_SIZE too.
Only simple tests have been run so far:
time for i in $(seq 1 1000000); do echo $i >> /root/ordered.txt; done
real 0m21.392s
user 0m8.077s
sys 0m13.098s
du -h /root/ordered.txt
6.6M /root/ordered.txt
sha1sum /root/ordered.txt
2dcc06b7ca3b7dd8b5626af83c1be3cb08ddc76c /root/ordered.txt
stat /root/ordered.txt
File: /root/ordered.txt
Size: 6888896 Blocks: 13456 IO Block: 4096 regular file
Device: 254,1 Inode: 655717 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2023-04-21 19:34:20.709869093 +0000
Modify: 2023-04-21 19:34:43.833900042 +0000
Change: 2023-04-21 19:34:43.833900042 +0000
Birth: 2023-04-21 19:34:20.709869093 +0000
8 KiB block size:
sha1sum /root/ordered.txt
mount -t tmpfs -o size=10M,bsize=$((4096*2)) -o noswap tmpfs /data-tmpfs/
cp /root/ordered.txt
sha1sum /data-tmpfs/ordered.txt
stat /data-tmpfs/ordered.txt
2dcc06b7ca3b7dd8b5626af83c1be3cb08ddc76c /root/ordered.txt
2dcc06b7ca3b7dd8b5626af83c1be3cb08ddc76c /data-tmpfs/ordered.txt
File: /data-tmpfs/ordered.txt
Size: 6888896 Blocks: 13456 IO Block: 8192 regular file
Device: 0,42 Inode: 2 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2023-04-21 19:31:16.078390405 +0000
Modify: 2023-04-21 19:31:16.070391363 +0000
Change: 2023-04-21 19:31:16.070391363 +0000
Birth: 2023-04-21 19:31:16.034395676 +0000
64 KiB block size:
sha1sum /root/ordered.txt
mount -t tmpfs -o size=10M,bsize=$((4096*16)) -o noswap tmpfs /data-tmpfs/
cp /root/ordered.txt /data-tmpfs/; sha1sum /data-tmpfs/ordered.txt
stat /data-tmpfs/ordered.txt
2dcc06b7ca3b7dd8b5626af83c1be3cb08ddc76c /root/ordered.txt
2dcc06b7ca3b7dd8b5626af83c1be3cb08ddc76c /data-tmpfs/ordered.txt
File: /data-tmpfs/ordered.txt
Size: 6888896 Blocks: 13568 IO Block: 65536 regular file
Device: 0,42 Inode: 2 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2023-04-21 19:32:14.669796970 +0000
Modify: 2023-04-21 19:32:14.661796959 +0000
Change: 2023-04-21 19:32:14.661796959 +0000
Birth: 2023-04-21 19:32:14.649796944 +0000
Signed-off-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
---
mm/shmem.c | 47 ++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 42 insertions(+), 5 deletions(-)
diff --git a/mm/shmem.c b/mm/shmem.c
index 740b4448f936..64108c28eebd 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -118,11 +118,13 @@ struct shmem_options {
int huge;
int seen;
bool noswap;
+ u64 blocksize;
#define SHMEM_SEEN_BLOCKS 1
#define SHMEM_SEEN_INODES 2
#define SHMEM_SEEN_HUGE 4
#define SHMEM_SEEN_INUMS 8
#define SHMEM_SEEN_NOSWAP 16
+#define SHMEM_SEEN_BLOCKSIZE 32
};
static u64 shmem_default_bsize(void)
@@ -3779,6 +3781,7 @@ enum shmem_param {
Opt_inode32,
Opt_inode64,
Opt_noswap,
+ Opt_bsize,
};
static const struct constant_table shmem_param_enums_huge[] = {
@@ -3801,6 +3804,7 @@ const struct fs_parameter_spec shmem_fs_parameters[] = {
fsparam_flag ("inode32", Opt_inode32),
fsparam_flag ("inode64", Opt_inode64),
fsparam_flag ("noswap", Opt_noswap),
+ fsparam_u32 ("bsize", Opt_bsize),
{}
};
@@ -3827,7 +3831,14 @@ static int shmem_parse_one(struct fs_context *fc, struct fs_parameter *param)
}
if (*rest)
goto bad_value;
- ctx->blocks = DIV_ROUND_UP(size, shmem_default_bsize());
+ if (!(ctx->seen & SHMEM_SEEN_BLOCKSIZE) ||
+ ctx->blocksize == shmem_default_bsize())
+ ctx->blocks = DIV_ROUND_UP(size, shmem_default_bsize());
+ else {
+ if (size < ctx->blocksize || size % ctx->blocksize != 0)
+ goto bad_value;
+ ctx->blocks = DIV_ROUND_UP(size, ctx->blocksize);
+ }
ctx->seen |= SHMEM_SEEN_BLOCKS;
break;
case Opt_nr_blocks:
@@ -3892,6 +3903,23 @@ static int shmem_parse_one(struct fs_context *fc, struct fs_parameter *param)
ctx->noswap = true;
ctx->seen |= SHMEM_SEEN_NOSWAP;
break;
+ case Opt_bsize:
+ ctx->blocksize = result.uint_32;
+ ctx->seen |= SHMEM_SEEN_BLOCKSIZE;
+ /* Must be >= PAGE_SIZE */
+ if (ctx->blocksize < PAGE_SIZE)
+ goto bad_value;
+ /*
+ * We cap this to allow a block to be at least allowed to
+ * be allocated using the buddy allocator. That's MAX_ORDER
+ * pages. So 4 MiB on x86_64.
+ */
+ if (ctx->blocksize > (1 << (MAX_ORDER + PAGE_SHIFT)))
+ goto bad_value;
+ /* The blocksize must be a multiple of the page size so must be aligned */
+ if (!PAGE_ALIGNED(ctx->blocksize))
+ goto bad_value;
+ break;
}
return 0;
@@ -3963,6 +3991,12 @@ static int shmem_reconfigure(struct fs_context *fc)
raw_spin_lock(&sbinfo->stat_lock);
inodes = sbinfo->max_inodes - sbinfo->free_inodes;
+ if (ctx->seen & SHMEM_SEEN_BLOCKSIZE) {
+ if (ctx->blocksize != shmem_sb_blocksize(sbinfo)) {
+ err = "Cannot modify block size on remount";
+ goto out;
+ }
+ }
if ((ctx->seen & SHMEM_SEEN_BLOCKS) && ctx->blocks) {
if (!sbinfo->max_blocks) {
err = "Cannot retroactively limit size";
@@ -4078,6 +4112,8 @@ static int shmem_show_options(struct seq_file *seq, struct dentry *root)
shmem_show_mpol(seq, sbinfo->mpol);
if (sbinfo->noswap)
seq_printf(seq, ",noswap");
+ if (shmem_sb_blocksize(sbinfo) != shmem_default_bsize())
+ seq_printf(seq, ",bsize=%llu", shmem_sb_blocksize(sbinfo));
return 0;
}
@@ -4115,10 +4151,12 @@ static int shmem_fill_super(struct super_block *sb, struct fs_context *fc)
* but the internal instance is left unlimited.
*/
if (!(sb->s_flags & SB_KERNMOUNT)) {
+ if (!(ctx->seen & SHMEM_SEEN_BLOCKSIZE))
+ ctx->blocksize = shmem_default_bsize();
if (!(ctx->seen & SHMEM_SEEN_BLOCKS))
- ctx->blocks = shmem_default_max_blocks(shmem_default_bsize());
+ ctx->blocks = shmem_default_max_blocks(ctx->blocksize);
if (!(ctx->seen & SHMEM_SEEN_INODES))
- ctx->inodes = shmem_default_max_inodes(shmem_default_bsize());
+ ctx->inodes = shmem_default_max_inodes(ctx->blocksize);
if (!(ctx->seen & SHMEM_SEEN_INUMS))
ctx->full_inums = IS_ENABLED(CONFIG_TMPFS_INODE64);
sbinfo->noswap = ctx->noswap;
@@ -4127,7 +4165,7 @@ static int shmem_fill_super(struct super_block *sb, struct fs_context *fc)
}
sb->s_export_op = &shmem_export_ops;
sb->s_flags |= SB_NOSEC | SB_I_VERSION;
- sbinfo->blocksize = shmem_default_bsize();
+ sbinfo->blocksize = ctx->blocksize;
#else
sb->s_flags |= SB_NOUSER;
#endif
@@ -4155,7 +4193,6 @@ static int shmem_fill_super(struct super_block *sb, struct fs_context *fc)
sb->s_maxbytes = MAX_LFS_FILESIZE;
sb->s_blocksize = shmem_sb_blocksize(sbinfo);
sb->s_blocksize_bits = __ffs(sb->s_blocksize);
- WARN_ON_ONCE(sb->s_blocksize_bits != PAGE_SHIFT);
sb->s_magic = TMPFS_MAGIC;
sb->s_op = &shmem_ops;
sb->s_time_gran = 1;
--
2.39.2