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Commit 724bb09f authored by Al Viro's avatar Al Viro
Browse files

ufs: don't use lock_ufs() for block pointers tree protection 



* 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: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 4af7b2c0

fs/ufs/balloc.c

+4 −0
Original line number Diff line number Diff line
@@ -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);
@@ -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);

fs/ufs/inode.c

+93 −45
Original line number Diff line number Diff line
@@ -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;
@@ -75,12 +73,53 @@ 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;
@@ -88,12 +127,10 @@ static u64 ufs_frag_map(struct inode *inode, sector_t frag, bool needs_lock) 
	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",
@@ -101,59 +138,73 @@ static u64 ufs_frag_map(struct inode *inode, sector_t frag, bool needs_lock) 
		(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;

}



/**
@@ -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);
@@ -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 >
@@ -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;

fs/ufs/super.c

+2 −0
Original line number Diff line number Diff line
@@ -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;

}

fs/ufs/truncate.c

+20 −2
Original line number Diff line number Diff line
@@ -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;
@@ -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);
@@ -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;

	}
@@ -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;
@@ -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);
@@ -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;

	}
@@ -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);
@@ -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;

	}
@@ -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);
@@ -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,
@@ -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)

fs/ufs/ufs.h

+2 −0
Original line number Diff line number Diff line
@@ -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;

};