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indirect.c
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indirect.c
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// SPDX-License-Identifier: GPL-2.0
/*
* linux/fs/ext4/indirect.c
*
* from
*
* linux/fs/ext4/inode.c
*
* Copyright (C) 1992, 1993, 1994, 1995
* Remy Card ([email protected])
* Laboratoire MASI - Institut Blaise Pascal
* Universite Pierre et Marie Curie (Paris VI)
*
* from
*
* linux/fs/minix/inode.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*
* Goal-directed block allocation by Stephen Tweedie
* ([email protected]), 1993, 1998
*/
#include "ext4_jbd2.h"
#include "truncate.h"
#include <linux/dax.h>
#include <linux/uio.h>
#include <trace/events/ext4.h>
typedef struct {
__le32 *p;
__le32 key;
struct buffer_head *bh;
} Indirect;
static inline void add_chain(Indirect *p, struct buffer_head *bh, __le32 *v)
{
p->key = *(p->p = v);
p->bh = bh;
}
/**
* ext4_block_to_path - parse the block number into array of offsets
* @inode: inode in question (we are only interested in its superblock)
* @i_block: block number to be parsed
* @offsets: array to store the offsets in
* @boundary: set this non-zero if the referred-to block is likely to be
* followed (on disk) by an indirect block.
*
* To store the locations of file's data ext4 uses a data structure common
* for UNIX filesystems - tree of pointers anchored in the inode, with
* data blocks at leaves and indirect blocks in intermediate nodes.
* This function translates the block number into path in that tree -
* return value is the path length and @offsets[n] is the offset of
* pointer to (n+1)th node in the nth one. If @block is out of range
* (negative or too large) warning is printed and zero returned.
*
* Note: function doesn't find node addresses, so no IO is needed. All
* we need to know is the capacity of indirect blocks (taken from the
* inode->i_sb).
*/
/*
* Portability note: the last comparison (check that we fit into triple
* indirect block) is spelled differently, because otherwise on an
* architecture with 32-bit longs and 8Kb pages we might get into trouble
* if our filesystem had 8Kb blocks. We might use long long, but that would
* kill us on x86. Oh, well, at least the sign propagation does not matter -
* i_block would have to be negative in the very beginning, so we would not
* get there at all.
*/
static int ext4_block_to_path(struct inode *inode,
ext4_lblk_t i_block,
ext4_lblk_t offsets[4], int *boundary)
{
int ptrs = EXT4_ADDR_PER_BLOCK(inode->i_sb);
int ptrs_bits = EXT4_ADDR_PER_BLOCK_BITS(inode->i_sb);
const long direct_blocks = EXT4_NDIR_BLOCKS,
indirect_blocks = ptrs,
double_blocks = (1 << (ptrs_bits * 2));
int n = 0;
int final = 0;
if (i_block < direct_blocks) {
offsets[n++] = i_block;
final = direct_blocks;
} else if ((i_block -= direct_blocks) < indirect_blocks) {
offsets[n++] = EXT4_IND_BLOCK;
offsets[n++] = i_block;
final = ptrs;
} else if ((i_block -= indirect_blocks) < double_blocks) {
offsets[n++] = EXT4_DIND_BLOCK;
offsets[n++] = i_block >> ptrs_bits;
offsets[n++] = i_block & (ptrs - 1);
final = ptrs;
} else if (((i_block -= double_blocks) >> (ptrs_bits * 2)) < ptrs) {
offsets[n++] = EXT4_TIND_BLOCK;
offsets[n++] = i_block >> (ptrs_bits * 2);
offsets[n++] = (i_block >> ptrs_bits) & (ptrs - 1);
offsets[n++] = i_block & (ptrs - 1);
final = ptrs;
} else {
ext4_warning(inode->i_sb, "block %lu > max in inode %lu",
i_block + direct_blocks +
indirect_blocks + double_blocks, inode->i_ino);
}
if (boundary)
*boundary = final - 1 - (i_block & (ptrs - 1));
return n;
}
/**
* ext4_get_branch - read the chain of indirect blocks leading to data
* @inode: inode in question
* @depth: depth of the chain (1 - direct pointer, etc.)
* @offsets: offsets of pointers in inode/indirect blocks
* @chain: place to store the result
* @err: here we store the error value
*
* Function fills the array of triples <key, p, bh> and returns %NULL
* if everything went OK or the pointer to the last filled triple
* (incomplete one) otherwise. Upon the return chain[i].key contains
* the number of (i+1)-th block in the chain (as it is stored in memory,
* i.e. little-endian 32-bit), chain[i].p contains the address of that
* number (it points into struct inode for i==0 and into the bh->b_data
* for i>0) and chain[i].bh points to the buffer_head of i-th indirect
* block for i>0 and NULL for i==0. In other words, it holds the block
* numbers of the chain, addresses they were taken from (and where we can
* verify that chain did not change) and buffer_heads hosting these
* numbers.
*
* Function stops when it stumbles upon zero pointer (absent block)
* (pointer to last triple returned, *@err == 0)
* or when it gets an IO error reading an indirect block
* (ditto, *@err == -EIO)
* or when it reads all @depth-1 indirect blocks successfully and finds
* the whole chain, all way to the data (returns %NULL, *err == 0).
*
* Need to be called with
* down_read(&EXT4_I(inode)->i_data_sem)
*/
static Indirect *ext4_get_branch(struct inode *inode, int depth,
ext4_lblk_t *offsets,
Indirect chain[4], int *err)
{
struct super_block *sb = inode->i_sb;
Indirect *p = chain;
struct buffer_head *bh;
unsigned int key;
int ret = -EIO;
*err = 0;
/* i_data is not going away, no lock needed */
add_chain(chain, NULL, EXT4_I(inode)->i_data + *offsets);
if (!p->key)
goto no_block;
while (--depth) {
key = le32_to_cpu(p->key);
if (key > ext4_blocks_count(EXT4_SB(sb)->s_es)) {
/* the block was out of range */
ret = -EFSCORRUPTED;
goto failure;
}
bh = sb_getblk(sb, key);
if (unlikely(!bh)) {
ret = -ENOMEM;
goto failure;
}
if (!bh_uptodate_or_lock(bh)) {
if (ext4_read_bh(bh, 0, NULL) < 0) {
put_bh(bh);
goto failure;
}
/* validate block references */
if (ext4_check_indirect_blockref(inode, bh)) {
put_bh(bh);
goto failure;
}
}
add_chain(++p, bh, (__le32 *)bh->b_data + *++offsets);
/* Reader: end */
if (!p->key)
goto no_block;
}
return NULL;
failure:
*err = ret;
no_block:
return p;
}
/**
* ext4_find_near - find a place for allocation with sufficient locality
* @inode: owner
* @ind: descriptor of indirect block.
*
* This function returns the preferred place for block allocation.
* It is used when heuristic for sequential allocation fails.
* Rules are:
* + if there is a block to the left of our position - allocate near it.
* + if pointer will live in indirect block - allocate near that block.
* + if pointer will live in inode - allocate in the same
* cylinder group.
*
* In the latter case we colour the starting block by the callers PID to
* prevent it from clashing with concurrent allocations for a different inode
* in the same block group. The PID is used here so that functionally related
* files will be close-by on-disk.
*
* Caller must make sure that @ind is valid and will stay that way.
*/
static ext4_fsblk_t ext4_find_near(struct inode *inode, Indirect *ind)
{
struct ext4_inode_info *ei = EXT4_I(inode);
__le32 *start = ind->bh ? (__le32 *) ind->bh->b_data : ei->i_data;
__le32 *p;
/* Try to find previous block */
for (p = ind->p - 1; p >= start; p--) {
if (*p)
return le32_to_cpu(*p);
}
/* No such thing, so let's try location of indirect block */
if (ind->bh)
return ind->bh->b_blocknr;
/*
* It is going to be referred to from the inode itself? OK, just put it
* into the same cylinder group then.
*/
return ext4_inode_to_goal_block(inode);
}
/**
* ext4_find_goal - find a preferred place for allocation.
* @inode: owner
* @block: block we want
* @partial: pointer to the last triple within a chain
*
* Normally this function find the preferred place for block allocation,
* returns it.
* Because this is only used for non-extent files, we limit the block nr
* to 32 bits.
*/
static ext4_fsblk_t ext4_find_goal(struct inode *inode, ext4_lblk_t block,
Indirect *partial)
{
ext4_fsblk_t goal;
/*
* XXX need to get goal block from mballoc's data structures
*/
goal = ext4_find_near(inode, partial);
goal = goal & EXT4_MAX_BLOCK_FILE_PHYS;
return goal;
}
/**
* ext4_blks_to_allocate - Look up the block map and count the number
* of direct blocks need to be allocated for the given branch.
*
* @branch: chain of indirect blocks
* @k: number of blocks need for indirect blocks
* @blks: number of data blocks to be mapped.
* @blocks_to_boundary: the offset in the indirect block
*
* return the total number of blocks to be allocate, including the
* direct and indirect blocks.
*/
static int ext4_blks_to_allocate(Indirect *branch, int k, unsigned int blks,
int blocks_to_boundary)
{
unsigned int count = 0;
/*
* Simple case, [t,d]Indirect block(s) has not allocated yet
* then it's clear blocks on that path have not allocated
*/
if (k > 0) {
/* right now we don't handle cross boundary allocation */
if (blks < blocks_to_boundary + 1)
count += blks;
else
count += blocks_to_boundary + 1;
return count;
}
count++;
while (count < blks && count <= blocks_to_boundary &&
le32_to_cpu(*(branch[0].p + count)) == 0) {
count++;
}
return count;
}
/**
* ext4_alloc_branch() - allocate and set up a chain of blocks
* @handle: handle for this transaction
* @ar: structure describing the allocation request
* @indirect_blks: number of allocated indirect blocks
* @offsets: offsets (in the blocks) to store the pointers to next.
* @branch: place to store the chain in.
*
* This function allocates blocks, zeroes out all but the last one,
* links them into chain and (if we are synchronous) writes them to disk.
* In other words, it prepares a branch that can be spliced onto the
* inode. It stores the information about that chain in the branch[], in
* the same format as ext4_get_branch() would do. We are calling it after
* we had read the existing part of chain and partial points to the last
* triple of that (one with zero ->key). Upon the exit we have the same
* picture as after the successful ext4_get_block(), except that in one
* place chain is disconnected - *branch->p is still zero (we did not
* set the last link), but branch->key contains the number that should
* be placed into *branch->p to fill that gap.
*
* If allocation fails we free all blocks we've allocated (and forget
* their buffer_heads) and return the error value the from failed
* ext4_alloc_block() (normally -ENOSPC). Otherwise we set the chain
* as described above and return 0.
*/
static int ext4_alloc_branch(handle_t *handle,
struct ext4_allocation_request *ar,
int indirect_blks, ext4_lblk_t *offsets,
Indirect *branch)
{
struct buffer_head * bh;
ext4_fsblk_t b, new_blocks[4];
__le32 *p;
int i, j, err, len = 1;
for (i = 0; i <= indirect_blks; i++) {
if (i == indirect_blks) {
new_blocks[i] = ext4_mb_new_blocks(handle, ar, &err);
} else {
ar->goal = new_blocks[i] = ext4_new_meta_blocks(handle,
ar->inode, ar->goal,
ar->flags & EXT4_MB_DELALLOC_RESERVED,
NULL, &err);
/* Simplify error cleanup... */
branch[i+1].bh = NULL;
}
if (err) {
i--;
goto failed;
}
branch[i].key = cpu_to_le32(new_blocks[i]);
if (i == 0)
continue;
bh = branch[i].bh = sb_getblk(ar->inode->i_sb, new_blocks[i-1]);
if (unlikely(!bh)) {
err = -ENOMEM;
goto failed;
}
lock_buffer(bh);
BUFFER_TRACE(bh, "call get_create_access");
err = ext4_journal_get_create_access(handle, ar->inode->i_sb,
bh, EXT4_JTR_NONE);
if (err) {
unlock_buffer(bh);
goto failed;
}
memset(bh->b_data, 0, bh->b_size);
p = branch[i].p = (__le32 *) bh->b_data + offsets[i];
b = new_blocks[i];
if (i == indirect_blks)
len = ar->len;
for (j = 0; j < len; j++)
*p++ = cpu_to_le32(b++);
BUFFER_TRACE(bh, "marking uptodate");
set_buffer_uptodate(bh);
unlock_buffer(bh);
BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
err = ext4_handle_dirty_metadata(handle, ar->inode, bh);
if (err)
goto failed;
}
return 0;
failed:
if (i == indirect_blks) {
/* Free data blocks */
ext4_free_blocks(handle, ar->inode, NULL, new_blocks[i],
ar->len, 0);
i--;
}
for (; i >= 0; i--) {
/*
* We want to ext4_forget() only freshly allocated indirect
* blocks. Buffer for new_blocks[i] is at branch[i+1].bh
* (buffer at branch[0].bh is indirect block / inode already
* existing before ext4_alloc_branch() was called). Also
* because blocks are freshly allocated, we don't need to
* revoke them which is why we don't set
* EXT4_FREE_BLOCKS_METADATA.
*/
ext4_free_blocks(handle, ar->inode, branch[i+1].bh,
new_blocks[i], 1,
branch[i+1].bh ? EXT4_FREE_BLOCKS_FORGET : 0);
}
return err;
}
/**
* ext4_splice_branch() - splice the allocated branch onto inode.
* @handle: handle for this transaction
* @ar: structure describing the allocation request
* @where: location of missing link
* @num: number of indirect blocks we are adding
*
* This function fills the missing link and does all housekeeping needed in
* inode (->i_blocks, etc.). In case of success we end up with the full
* chain to new block and return 0.
*/
static int ext4_splice_branch(handle_t *handle,
struct ext4_allocation_request *ar,
Indirect *where, int num)
{
int i;
int err = 0;
ext4_fsblk_t current_block;
/*
* If we're splicing into a [td]indirect block (as opposed to the
* inode) then we need to get write access to the [td]indirect block
* before the splice.
*/
if (where->bh) {
BUFFER_TRACE(where->bh, "get_write_access");
err = ext4_journal_get_write_access(handle, ar->inode->i_sb,
where->bh, EXT4_JTR_NONE);
if (err)
goto err_out;
}
/* That's it */
*where->p = where->key;
/*
* Update the host buffer_head or inode to point to more just allocated
* direct blocks blocks
*/
if (num == 0 && ar->len > 1) {
current_block = le32_to_cpu(where->key) + 1;
for (i = 1; i < ar->len; i++)
*(where->p + i) = cpu_to_le32(current_block++);
}
/* We are done with atomic stuff, now do the rest of housekeeping */
/* had we spliced it onto indirect block? */
if (where->bh) {
/*
* If we spliced it onto an indirect block, we haven't
* altered the inode. Note however that if it is being spliced
* onto an indirect block at the very end of the file (the
* file is growing) then we *will* alter the inode to reflect
* the new i_size. But that is not done here - it is done in
* generic_commit_write->__mark_inode_dirty->ext4_dirty_inode.
*/
ext4_debug("splicing indirect only\n");
BUFFER_TRACE(where->bh, "call ext4_handle_dirty_metadata");
err = ext4_handle_dirty_metadata(handle, ar->inode, where->bh);
if (err)
goto err_out;
} else {
/*
* OK, we spliced it into the inode itself on a direct block.
*/
err = ext4_mark_inode_dirty(handle, ar->inode);
if (unlikely(err))
goto err_out;
ext4_debug("splicing direct\n");
}
return err;
err_out:
for (i = 1; i <= num; i++) {
/*
* branch[i].bh is newly allocated, so there is no
* need to revoke the block, which is why we don't
* need to set EXT4_FREE_BLOCKS_METADATA.
*/
ext4_free_blocks(handle, ar->inode, where[i].bh, 0, 1,
EXT4_FREE_BLOCKS_FORGET);
}
ext4_free_blocks(handle, ar->inode, NULL, le32_to_cpu(where[num].key),
ar->len, 0);
return err;
}
/*
* The ext4_ind_map_blocks() function handles non-extents inodes
* (i.e., using the traditional indirect/double-indirect i_blocks
* scheme) for ext4_map_blocks().
*
* Allocation strategy is simple: if we have to allocate something, we will
* have to go the whole way to leaf. So let's do it before attaching anything
* to tree, set linkage between the newborn blocks, write them if sync is
* required, recheck the path, free and repeat if check fails, otherwise
* set the last missing link (that will protect us from any truncate-generated
* removals - all blocks on the path are immune now) and possibly force the
* write on the parent block.
* That has a nice additional property: no special recovery from the failed
* allocations is needed - we simply release blocks and do not touch anything
* reachable from inode.
*
* `handle' can be NULL if create == 0.
*
* return > 0, # of blocks mapped or allocated.
* return = 0, if plain lookup failed.
* return < 0, error case.
*
* The ext4_ind_get_blocks() function should be called with
* down_write(&EXT4_I(inode)->i_data_sem) if allocating filesystem
* blocks (i.e., flags has EXT4_GET_BLOCKS_CREATE set) or
* down_read(&EXT4_I(inode)->i_data_sem) if not allocating file system
* blocks.
*/
int ext4_ind_map_blocks(handle_t *handle, struct inode *inode,
struct ext4_map_blocks *map,
int flags)
{
struct ext4_allocation_request ar;
int err = -EIO;
ext4_lblk_t offsets[4];
Indirect chain[4];
Indirect *partial;
int indirect_blks;
int blocks_to_boundary = 0;
int depth;
int count = 0;
ext4_fsblk_t first_block = 0;
trace_ext4_ind_map_blocks_enter(inode, map->m_lblk, map->m_len, flags);
ASSERT(!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)));
ASSERT(handle != NULL || (flags & EXT4_GET_BLOCKS_CREATE) == 0);
depth = ext4_block_to_path(inode, map->m_lblk, offsets,
&blocks_to_boundary);
if (depth == 0)
goto out;
partial = ext4_get_branch(inode, depth, offsets, chain, &err);
/* Simplest case - block found, no allocation needed */
if (!partial) {
first_block = le32_to_cpu(chain[depth - 1].key);
count++;
/*map more blocks*/
while (count < map->m_len && count <= blocks_to_boundary) {
ext4_fsblk_t blk;
blk = le32_to_cpu(*(chain[depth-1].p + count));
if (blk == first_block + count)
count++;
else
break;
}
goto got_it;
}
/* Next simple case - plain lookup failed */
if ((flags & EXT4_GET_BLOCKS_CREATE) == 0) {
unsigned epb = inode->i_sb->s_blocksize / sizeof(u32);
int i;
/*
* Count number blocks in a subtree under 'partial'. At each
* level we count number of complete empty subtrees beyond
* current offset and then descend into the subtree only
* partially beyond current offset.
*/
count = 0;
for (i = partial - chain + 1; i < depth; i++)
count = count * epb + (epb - offsets[i] - 1);
count++;
/* Fill in size of a hole we found */
map->m_pblk = 0;
map->m_len = min_t(unsigned int, map->m_len, count);
goto cleanup;
}
/* Failed read of indirect block */
if (err == -EIO)
goto cleanup;
/*
* Okay, we need to do block allocation.
*/
if (ext4_has_feature_bigalloc(inode->i_sb)) {
EXT4_ERROR_INODE(inode, "Can't allocate blocks for "
"non-extent mapped inodes with bigalloc");
err = -EFSCORRUPTED;
goto out;
}
/* Set up for the direct block allocation */
memset(&ar, 0, sizeof(ar));
ar.inode = inode;
ar.logical = map->m_lblk;
if (S_ISREG(inode->i_mode))
ar.flags = EXT4_MB_HINT_DATA;
if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
ar.flags |= EXT4_MB_DELALLOC_RESERVED;
if (flags & EXT4_GET_BLOCKS_METADATA_NOFAIL)
ar.flags |= EXT4_MB_USE_RESERVED;
ar.goal = ext4_find_goal(inode, map->m_lblk, partial);
/* the number of blocks need to allocate for [d,t]indirect blocks */
indirect_blks = (chain + depth) - partial - 1;
/*
* Next look up the indirect map to count the totoal number of
* direct blocks to allocate for this branch.
*/
ar.len = ext4_blks_to_allocate(partial, indirect_blks,
map->m_len, blocks_to_boundary);
/*
* Block out ext4_truncate while we alter the tree
*/
err = ext4_alloc_branch(handle, &ar, indirect_blks,
offsets + (partial - chain), partial);
/*
* The ext4_splice_branch call will free and forget any buffers
* on the new chain if there is a failure, but that risks using
* up transaction credits, especially for bitmaps where the
* credits cannot be returned. Can we handle this somehow? We
* may need to return -EAGAIN upwards in the worst case. --sct
*/
if (!err)
err = ext4_splice_branch(handle, &ar, partial, indirect_blks);
if (err)
goto cleanup;
map->m_flags |= EXT4_MAP_NEW;
ext4_update_inode_fsync_trans(handle, inode, 1);
count = ar.len;
/*
* Update reserved blocks/metadata blocks after successful block
* allocation which had been deferred till now.
*/
if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
ext4_da_update_reserve_space(inode, count, 1);
got_it:
map->m_flags |= EXT4_MAP_MAPPED;
map->m_pblk = le32_to_cpu(chain[depth-1].key);
map->m_len = count;
if (count > blocks_to_boundary)
map->m_flags |= EXT4_MAP_BOUNDARY;
err = count;
/* Clean up and exit */
partial = chain + depth - 1; /* the whole chain */
cleanup:
while (partial > chain) {
BUFFER_TRACE(partial->bh, "call brelse");
brelse(partial->bh);
partial--;
}
out:
trace_ext4_ind_map_blocks_exit(inode, flags, map, err);
return err;
}
/*
* Calculate number of indirect blocks touched by mapping @nrblocks logically
* contiguous blocks
*/
int ext4_ind_trans_blocks(struct inode *inode, int nrblocks)
{
/*
* With N contiguous data blocks, we need at most
* N/EXT4_ADDR_PER_BLOCK(inode->i_sb) + 1 indirect blocks,
* 2 dindirect blocks, and 1 tindirect block
*/
return DIV_ROUND_UP(nrblocks, EXT4_ADDR_PER_BLOCK(inode->i_sb)) + 4;
}
static int ext4_ind_trunc_restart_fn(handle_t *handle, struct inode *inode,
struct buffer_head *bh, int *dropped)
{
int err;
if (bh) {
BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
err = ext4_handle_dirty_metadata(handle, inode, bh);
if (unlikely(err))
return err;
}
err = ext4_mark_inode_dirty(handle, inode);
if (unlikely(err))
return err;
/*
* Drop i_data_sem to avoid deadlock with ext4_map_blocks. At this
* moment, get_block can be called only for blocks inside i_size since
* page cache has been already dropped and writes are blocked by
* i_rwsem. So we can safely drop the i_data_sem here.
*/
BUG_ON(EXT4_JOURNAL(inode) == NULL);
ext4_discard_preallocations(inode);
up_write(&EXT4_I(inode)->i_data_sem);
*dropped = 1;
return 0;
}
/*
* Truncate transactions can be complex and absolutely huge. So we need to
* be able to restart the transaction at a convenient checkpoint to make
* sure we don't overflow the journal.
*
* Try to extend this transaction for the purposes of truncation. If
* extend fails, we restart transaction.
*/
static int ext4_ind_truncate_ensure_credits(handle_t *handle,
struct inode *inode,
struct buffer_head *bh,
int revoke_creds)
{
int ret;
int dropped = 0;
ret = ext4_journal_ensure_credits_fn(handle, EXT4_RESERVE_TRANS_BLOCKS,
ext4_blocks_for_truncate(inode), revoke_creds,
ext4_ind_trunc_restart_fn(handle, inode, bh, &dropped));
if (dropped)
down_write(&EXT4_I(inode)->i_data_sem);
if (ret <= 0)
return ret;
if (bh) {
BUFFER_TRACE(bh, "retaking write access");
ret = ext4_journal_get_write_access(handle, inode->i_sb, bh,
EXT4_JTR_NONE);
if (unlikely(ret))
return ret;
}
return 0;
}
/*
* Probably it should be a library function... search for first non-zero word
* or memcmp with zero_page, whatever is better for particular architecture.
* Linus?
*/
static inline int all_zeroes(__le32 *p, __le32 *q)
{
while (p < q)
if (*p++)
return 0;
return 1;
}
/**
* ext4_find_shared - find the indirect blocks for partial truncation.
* @inode: inode in question
* @depth: depth of the affected branch
* @offsets: offsets of pointers in that branch (see ext4_block_to_path)
* @chain: place to store the pointers to partial indirect blocks
* @top: place to the (detached) top of branch
*
* This is a helper function used by ext4_truncate().
*
* When we do truncate() we may have to clean the ends of several
* indirect blocks but leave the blocks themselves alive. Block is
* partially truncated if some data below the new i_size is referred
* from it (and it is on the path to the first completely truncated
* data block, indeed). We have to free the top of that path along
* with everything to the right of the path. Since no allocation
* past the truncation point is possible until ext4_truncate()
* finishes, we may safely do the latter, but top of branch may
* require special attention - pageout below the truncation point
* might try to populate it.
*
* We atomically detach the top of branch from the tree, store the
* block number of its root in *@top, pointers to buffer_heads of
* partially truncated blocks - in @chain[].bh and pointers to
* their last elements that should not be removed - in
* @chain[].p. Return value is the pointer to last filled element
* of @chain.
*
* The work left to caller to do the actual freeing of subtrees:
* a) free the subtree starting from *@top
* b) free the subtrees whose roots are stored in
* (@chain[i].p+1 .. end of @chain[i].bh->b_data)
* c) free the subtrees growing from the inode past the @chain[0].
* (no partially truncated stuff there). */
static Indirect *ext4_find_shared(struct inode *inode, int depth,
ext4_lblk_t offsets[4], Indirect chain[4],
__le32 *top)
{
Indirect *partial, *p;
int k, err;
*top = 0;
/* Make k index the deepest non-null offset + 1 */
for (k = depth; k > 1 && !offsets[k-1]; k--)
;
partial = ext4_get_branch(inode, k, offsets, chain, &err);
/* Writer: pointers */
if (!partial)
partial = chain + k-1;
/*
* If the branch acquired continuation since we've looked at it -
* fine, it should all survive and (new) top doesn't belong to us.
*/
if (!partial->key && *partial->p)
/* Writer: end */
goto no_top;
for (p = partial; (p > chain) && all_zeroes((__le32 *) p->bh->b_data, p->p); p--)
;
/*
* OK, we've found the last block that must survive. The rest of our
* branch should be detached before unlocking. However, if that rest
* of branch is all ours and does not grow immediately from the inode
* it's easier to cheat and just decrement partial->p.
*/
if (p == chain + k - 1 && p > chain) {
p->p--;
} else {
*top = *p->p;
/* Nope, don't do this in ext4. Must leave the tree intact */
#if 0
*p->p = 0;
#endif
}
/* Writer: end */
while (partial > p) {
brelse(partial->bh);
partial--;
}
no_top:
return partial;
}
/*
* Zero a number of block pointers in either an inode or an indirect block.
* If we restart the transaction we must again get write access to the
* indirect block for further modification.
*
* We release `count' blocks on disk, but (last - first) may be greater
* than `count' because there can be holes in there.
*
* Return 0 on success, 1 on invalid block range
* and < 0 on fatal error.
*/
static int ext4_clear_blocks(handle_t *handle, struct inode *inode,
struct buffer_head *bh,
ext4_fsblk_t block_to_free,
unsigned long count, __le32 *first,
__le32 *last)
{
__le32 *p;
int flags = EXT4_FREE_BLOCKS_VALIDATED;
int err;
if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode) ||
ext4_test_inode_flag(inode, EXT4_INODE_EA_INODE))
flags |= EXT4_FREE_BLOCKS_FORGET | EXT4_FREE_BLOCKS_METADATA;
else if (ext4_should_journal_data(inode))
flags |= EXT4_FREE_BLOCKS_FORGET;
if (!ext4_inode_block_valid(inode, block_to_free, count)) {
EXT4_ERROR_INODE(inode, "attempt to clear invalid "
"blocks %llu len %lu",
(unsigned long long) block_to_free, count);
return 1;
}
err = ext4_ind_truncate_ensure_credits(handle, inode, bh,
ext4_free_data_revoke_credits(inode, count));
if (err < 0)
goto out_err;
for (p = first; p < last; p++)
*p = 0;
ext4_free_blocks(handle, inode, NULL, block_to_free, count, flags);
return 0;
out_err:
ext4_std_error(inode->i_sb, err);
return err;
}
/**
* ext4_free_data - free a list of data blocks
* @handle: handle for this transaction
* @inode: inode we are dealing with
* @this_bh: indirect buffer_head which contains *@first and *@last
* @first: array of block numbers
* @last: points immediately past the end of array
*
* We are freeing all blocks referred from that array (numbers are stored as
* little-endian 32-bit) and updating @inode->i_blocks appropriately.
*
* We accumulate contiguous runs of blocks to free. Conveniently, if these
* blocks are contiguous then releasing them at one time will only affect one
* or two bitmap blocks (+ group descriptor(s) and superblock) and we won't
* actually use a lot of journal space.
*
* @this_bh will be %NULL if @first and @last point into the inode's direct
* block pointers.
*/
static void ext4_free_data(handle_t *handle, struct inode *inode,
struct buffer_head *this_bh,
__le32 *first, __le32 *last)
{
ext4_fsblk_t block_to_free = 0; /* Starting block # of a run */
unsigned long count = 0; /* Number of blocks in the run */
__le32 *block_to_free_p = NULL; /* Pointer into inode/ind
corresponding to
block_to_free */
ext4_fsblk_t nr; /* Current block # */
__le32 *p; /* Pointer into inode/ind
for current block */
int err = 0;
if (this_bh) { /* For indirect block */
BUFFER_TRACE(this_bh, "get_write_access");
err = ext4_journal_get_write_access(handle, inode->i_sb,
this_bh, EXT4_JTR_NONE);
/* Important: if we can't update the indirect pointers
* to the blocks, we can't free them. */
if (err)
return;
}
for (p = first; p < last; p++) {
nr = le32_to_cpu(*p);
if (nr) {
/* accumulate blocks to free if they're contiguous */
if (count == 0) {
block_to_free = nr;
block_to_free_p = p;
count = 1;
} else if (nr == block_to_free + count) {
count++;
} else {
err = ext4_clear_blocks(handle, inode, this_bh,
block_to_free, count,
block_to_free_p, p);
if (err)
break;
block_to_free = nr;
block_to_free_p = p;
count = 1;
}
}
}
if (!err && count > 0)
err = ext4_clear_blocks(handle, inode, this_bh, block_to_free,
count, block_to_free_p, p);
if (err < 0)
/* fatal error */
return;
if (this_bh) {
BUFFER_TRACE(this_bh, "call ext4_handle_dirty_metadata");
/*
* The buffer head should have an attached journal head at this
* point. However, if the data is corrupted and an indirect
* block pointed to itself, it would have been detached when
* the block was cleared. Check for this instead of OOPSing.
*/
if ((EXT4_JOURNAL(inode) == NULL) || bh2jh(this_bh))
ext4_handle_dirty_metadata(handle, inode, this_bh);
else
EXT4_ERROR_INODE(inode,
"circular indirect block detected at "
"block %llu",
(unsigned long long) this_bh->b_blocknr);
}
}
/**
* ext4_free_branches - free an array of branches
* @handle: JBD handle for this transaction
* @inode: inode we are dealing with
* @parent_bh: the buffer_head which contains *@first and *@last
* @first: array of block numbers
* @last: pointer immediately past the end of array