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ufs: don't use lock_ufs() for block pointers tree protection
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* stores to block pointers are under per-inode seqlock (meta_lock) and
mutex (truncate_mutex)
* fetches of block pointers are either under truncate_mutex, or wrapped
into seqretry loop on meta_lock
* all changes of ->i_size are under truncate_mutex and i_mutex
* all changes of ->i_lastfrag are under truncate_mutex

It's similar to what ext2 is doing; the main difference is that unlike
ext2 we can't rely upon the atomicity of stores into block pointers -
on UFS2 they are 64bit.  So we can't cut the corner when switching
a pointer from NULL to non-NULL as we could in ext2_splice_branch()
and need to use meta_lock on all modifications.

We use seqlock where ext2 uses rwlock; ext2 could probably also benefit
from such change...

Another non-trivial difference is that with UFS we *cannot* have reader
grab truncate_mutex in case of race - it has to keep retrying.  That
might be possible to change, but not until we lift tail unpacking
several levels up in call chain.

After that commit we do *NOT* hold fs-wide serialization on accesses
to block pointers anymore.  Moreover, lock_ufs() can become a normal
mutex now - it's only used on statfs, remount and sync_fs and none
of those uses are recursive.  As the matter of fact, *now* it can be
collapsed with ->s_lock, and be eventually replaced with saner
per-cylinder-group spinlocks, but that's a separate story.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Al Viro committed Jul 6, 2015
1 parent 4af7b2c commit 724bb09
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Showing 5 changed files with 121 additions and 47 deletions.
4 changes: 4 additions & 0 deletions fs/ufs/balloc.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -417,7 +417,9 @@ u64 ufs_new_fragments(struct inode *inode, void *p, u64 fragment,
if (oldcount == 0) {
result = ufs_alloc_fragments (inode, cgno, goal, count, err);
if (result) {
write_seqlock(&UFS_I(inode)->meta_lock);
ufs_cpu_to_data_ptr(sb, p, result);
write_sequnlock(&UFS_I(inode)->meta_lock);
*err = 0;
UFS_I(inode)->i_lastfrag =
max(UFS_I(inode)->i_lastfrag, fragment + count);
Expand Down Expand Up @@ -473,7 +475,9 @@ u64 ufs_new_fragments(struct inode *inode, void *p, u64 fragment,
ufs_change_blocknr(inode, fragment - oldcount, oldcount,
uspi->s_sbbase + tmp,
uspi->s_sbbase + result, locked_page);
write_seqlock(&UFS_I(inode)->meta_lock);
ufs_cpu_to_data_ptr(sb, p, result);
write_sequnlock(&UFS_I(inode)->meta_lock);
*err = 0;
UFS_I(inode)->i_lastfrag = max(UFS_I(inode)->i_lastfrag,
fragment + count);
Expand Down
138 changes: 93 additions & 45 deletions fs/ufs/inode.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -41,8 +41,6 @@
#include "swab.h"
#include "util.h"

static u64 ufs_frag_map(struct inode *inode, sector_t frag, bool needs_lock);

static int ufs_block_to_path(struct inode *inode, sector_t i_block, sector_t offsets[4])
{
struct ufs_sb_private_info *uspi = UFS_SB(inode->i_sb)->s_uspi;
Expand Down Expand Up @@ -75,85 +73,138 @@ static int ufs_block_to_path(struct inode *inode, sector_t i_block, sector_t off
return n;
}

typedef struct {
void *p;
union {
__fs32 key32;
__fs64 key64;
};
struct buffer_head *bh;
} Indirect;

static inline int grow_chain32(struct ufs_inode_info *ufsi,
struct buffer_head *bh, __fs32 *v,
Indirect *from, Indirect *to)
{
Indirect *p;
unsigned seq;
to->bh = bh;
do {
seq = read_seqbegin(&ufsi->meta_lock);
to->key32 = *(__fs32 *)(to->p = v);
for (p = from; p <= to && p->key32 == *(__fs32 *)p->p; p++)
;
} while (read_seqretry(&ufsi->meta_lock, seq));
return (p > to);
}

static inline int grow_chain64(struct ufs_inode_info *ufsi,
struct buffer_head *bh, __fs64 *v,
Indirect *from, Indirect *to)
{
Indirect *p;
unsigned seq;
to->bh = bh;
do {
seq = read_seqbegin(&ufsi->meta_lock);
to->key64 = *(__fs64 *)(to->p = v);
for (p = from; p <= to && p->key64 == *(__fs64 *)p->p; p++)
;
} while (read_seqretry(&ufsi->meta_lock, seq));
return (p > to);
}

/*
* Returns the location of the fragment from
* the beginning of the filesystem.
*/

static u64 ufs_frag_map(struct inode *inode, sector_t frag, bool needs_lock)
static u64 ufs_frag_map(struct inode *inode, sector_t frag)
{
struct ufs_inode_info *ufsi = UFS_I(inode);
struct super_block *sb = inode->i_sb;
struct ufs_sb_private_info *uspi = UFS_SB(sb)->s_uspi;
u64 mask = (u64) uspi->s_apbmask>>uspi->s_fpbshift;
int shift = uspi->s_apbshift-uspi->s_fpbshift;
sector_t offsets[4], *p;
Indirect chain[4], *q = chain;
int depth = ufs_block_to_path(inode, frag >> uspi->s_fpbshift, offsets);
u64 ret = 0L;
__fs32 block;
__fs64 u2_block = 0L;
unsigned flags = UFS_SB(sb)->s_flags;
u64 temp = 0L;
u64 res = 0;

UFSD(": frag = %llu depth = %d\n", (unsigned long long)frag, depth);
UFSD(": uspi->s_fpbshift = %d ,uspi->s_apbmask = %x, mask=%llx\n",
uspi->s_fpbshift, uspi->s_apbmask,
(unsigned long long)mask);

if (depth == 0)
return 0;
goto no_block;

again:
p = offsets;

if (needs_lock)
lock_ufs(sb);
if ((flags & UFS_TYPE_MASK) == UFS_TYPE_UFS2)
goto ufs2;

block = ufsi->i_u1.i_data[*p++];
if (!block)
goto out;
if (!grow_chain32(ufsi, NULL, &ufsi->i_u1.i_data[*p++], chain, q))
goto changed;
if (!q->key32)
goto no_block;
while (--depth) {
__fs32 *ptr;
struct buffer_head *bh;
sector_t n = *p++;

bh = sb_bread(sb, uspi->s_sbbase + fs32_to_cpu(sb, block)+(n>>shift));
bh = sb_bread(sb, uspi->s_sbbase +
fs32_to_cpu(sb, q->key32) + (n>>shift));
if (!bh)
goto out;
block = ((__fs32 *) bh->b_data)[n & mask];
brelse (bh);
if (!block)
goto out;
goto no_block;
ptr = (__fs32 *)bh->b_data + (n & mask);
if (!grow_chain32(ufsi, bh, ptr, chain, ++q))
goto changed;
if (!q->key32)
goto no_block;
}
ret = (u64) (uspi->s_sbbase + fs32_to_cpu(sb, block) + (frag & uspi->s_fpbmask));
goto out;
ufs2:
u2_block = ufsi->i_u1.u2_i_data[*p++];
if (!u2_block)
goto out;
res = fs32_to_cpu(sb, q->key32);
goto found;

ufs2:
if (!grow_chain64(ufsi, NULL, &ufsi->i_u1.u2_i_data[*p++], chain, q))
goto changed;
if (!q->key64)
goto no_block;

while (--depth) {
__fs64 *ptr;
struct buffer_head *bh;
sector_t n = *p++;


temp = (u64)(uspi->s_sbbase) + fs64_to_cpu(sb, u2_block);
bh = sb_bread(sb, temp +(u64) (n>>shift));
bh = sb_bread(sb, uspi->s_sbbase +
fs64_to_cpu(sb, q->key64) + (n>>shift));
if (!bh)
goto out;
u2_block = ((__fs64 *)bh->b_data)[n & mask];
brelse(bh);
if (!u2_block)
goto out;
goto no_block;
ptr = (__fs64 *)bh->b_data + (n & mask);
if (!grow_chain64(ufsi, bh, ptr, chain, ++q))
goto changed;
if (!q->key64)
goto no_block;
}
res = fs64_to_cpu(sb, q->key64);
found:
res += uspi->s_sbbase + (frag & uspi->s_fpbmask);
no_block:
while (q > chain) {
brelse(q->bh);
q--;
}
temp = (u64)uspi->s_sbbase + fs64_to_cpu(sb, u2_block);
ret = temp + (u64) (frag & uspi->s_fpbmask);
return res;

out:
if (needs_lock)
unlock_ufs(sb);
return ret;
changed:
while (q > chain) {
brelse(q->bh);
q--;
}
goto again;
}

/**
Expand Down Expand Up @@ -421,10 +472,9 @@ int ufs_getfrag_block(struct inode *inode, sector_t fragment, struct buffer_head
int ret, err, new;
unsigned long ptr,phys;
u64 phys64 = 0;
bool needs_lock = (sbi->mutex_owner != current);

if (!create) {
phys64 = ufs_frag_map(inode, fragment, needs_lock);
phys64 = ufs_frag_map(inode, fragment);
UFSD("phys64 = %llu\n", (unsigned long long)phys64);
if (phys64)
map_bh(bh_result, sb, phys64);
Expand All @@ -438,8 +488,7 @@ int ufs_getfrag_block(struct inode *inode, sector_t fragment, struct buffer_head
ret = 0;
bh = NULL;

if (needs_lock)
lock_ufs(sb);
mutex_lock(&UFS_I(inode)->truncate_mutex);

UFSD("ENTER, ino %lu, fragment %llu\n", inode->i_ino, (unsigned long long)fragment);
if (fragment >
Expand Down Expand Up @@ -501,8 +550,7 @@ int ufs_getfrag_block(struct inode *inode, sector_t fragment, struct buffer_head
set_buffer_new(bh_result);
map_bh(bh_result, sb, phys);
abort:
if (needs_lock)
unlock_ufs(sb);
mutex_unlock(&UFS_I(inode)->truncate_mutex);

return err;

Expand Down
2 changes: 2 additions & 0 deletions fs/ufs/super.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1429,6 +1429,8 @@ static struct inode *ufs_alloc_inode(struct super_block *sb)
return NULL;

ei->vfs_inode.i_version = 1;
seqlock_init(&ei->meta_lock);
mutex_init(&ei->truncate_mutex);
return &ei->vfs_inode;
}

Expand Down
22 changes: 20 additions & 2 deletions fs/ufs/truncate.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -128,7 +128,9 @@ static int ufs_trunc_direct(struct inode *inode)
tmp = ufs_data_ptr_to_cpu(sb, p);
if (!tmp)
continue;
write_seqlock(&ufsi->meta_lock);
ufs_data_ptr_clear(uspi, p);
write_sequnlock(&ufsi->meta_lock);

if (free_count == 0) {
frag_to_free = tmp;
Expand Down Expand Up @@ -157,7 +159,9 @@ static int ufs_trunc_direct(struct inode *inode)
if (!tmp )
ufs_panic(sb, "ufs_truncate_direct", "internal error");
frag4 = ufs_fragnum (frag4);
write_seqlock(&ufsi->meta_lock);
ufs_data_ptr_clear(uspi, p);
write_sequnlock(&ufsi->meta_lock);

ufs_free_fragments (inode, tmp, frag4);
mark_inode_dirty(inode);
Expand Down Expand Up @@ -199,7 +203,9 @@ static int ufs_trunc_indirect(struct inode *inode, u64 offset, void *p)
return 1;
}
if (!ind_ubh) {
write_seqlock(&UFS_I(inode)->meta_lock);
ufs_data_ptr_clear(uspi, p);
write_sequnlock(&UFS_I(inode)->meta_lock);
return 0;
}

Expand All @@ -210,7 +216,9 @@ static int ufs_trunc_indirect(struct inode *inode, u64 offset, void *p)
if (!tmp)
continue;

write_seqlock(&UFS_I(inode)->meta_lock);
ufs_data_ptr_clear(uspi, ind);
write_sequnlock(&UFS_I(inode)->meta_lock);
ubh_mark_buffer_dirty(ind_ubh);
if (free_count == 0) {
frag_to_free = tmp;
Expand All @@ -235,7 +243,9 @@ static int ufs_trunc_indirect(struct inode *inode, u64 offset, void *p)
break;
if (i >= uspi->s_apb) {
tmp = ufs_data_ptr_to_cpu(sb, p);
write_seqlock(&UFS_I(inode)->meta_lock);
ufs_data_ptr_clear(uspi, p);
write_sequnlock(&UFS_I(inode)->meta_lock);

ubh_bforget(ind_ubh);
ufs_free_blocks (inode, tmp, uspi->s_fpb);
Expand Down Expand Up @@ -278,7 +288,9 @@ static int ufs_trunc_dindirect(struct inode *inode, u64 offset, void *p)
return 1;
}
if (!dind_bh) {
write_seqlock(&UFS_I(inode)->meta_lock);
ufs_data_ptr_clear(uspi, p);
write_sequnlock(&UFS_I(inode)->meta_lock);
return 0;
}

Expand All @@ -297,7 +309,9 @@ static int ufs_trunc_dindirect(struct inode *inode, u64 offset, void *p)
break;
if (i >= uspi->s_apb) {
tmp = ufs_data_ptr_to_cpu(sb, p);
write_seqlock(&UFS_I(inode)->meta_lock);
ufs_data_ptr_clear(uspi, p);
write_sequnlock(&UFS_I(inode)->meta_lock);

ubh_bforget(dind_bh);
ufs_free_blocks(inode, tmp, uspi->s_fpb);
Expand Down Expand Up @@ -339,7 +353,9 @@ static int ufs_trunc_tindirect(struct inode *inode)
return 1;
}
if (!tind_bh) {
write_seqlock(&ufsi->meta_lock);
ufs_data_ptr_clear(uspi, p);
write_sequnlock(&ufsi->meta_lock);
return 0;
}

Expand All @@ -355,7 +371,9 @@ static int ufs_trunc_tindirect(struct inode *inode)
break;
if (i >= uspi->s_apb) {
tmp = ufs_data_ptr_to_cpu(sb, p);
write_seqlock(&ufsi->meta_lock);
ufs_data_ptr_clear(uspi, p);
write_sequnlock(&ufsi->meta_lock);

ubh_bforget(tind_bh);
ufs_free_blocks(inode, tmp, uspi->s_fpb);
Expand Down Expand Up @@ -447,7 +465,7 @@ static void __ufs_truncate_blocks(struct inode *inode)
struct ufs_sb_private_info *uspi = UFS_SB(sb)->s_uspi;
int retry;

lock_ufs(sb);
mutex_lock(&ufsi->truncate_mutex);
while (1) {
retry = ufs_trunc_direct(inode);
retry |= ufs_trunc_indirect(inode, UFS_IND_BLOCK,
Expand All @@ -465,7 +483,7 @@ static void __ufs_truncate_blocks(struct inode *inode)
}

ufsi->i_lastfrag = DIRECT_FRAGMENT;
unlock_ufs(sb);
mutex_unlock(&ufsi->truncate_mutex);
}

int ufs_truncate(struct inode *inode, loff_t size)
Expand Down
2 changes: 2 additions & 0 deletions fs/ufs/ufs.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -46,6 +46,8 @@ struct ufs_inode_info {
__u32 i_oeftflag;
__u16 i_osync;
__u64 i_lastfrag;
seqlock_t meta_lock;
struct mutex truncate_mutex;
__u32 i_dir_start_lookup;
struct inode vfs_inode;
};
Expand Down

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