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Message-Id: <9AB08A26-272F-4CB8-BAF8-90B3E1957E47@dilger.ca>
Date: Thu, 18 Jul 2019 00:30:31 -0600
From: Andreas Dilger <adilger@...ger.ca>
To: Theodore Ts'o <tytso@....edu>
Cc: Ext4 Developers List <linux-ext4@...r.kernel.org>,
artem.blagodarenko@...il.com, stable@...nel.org
Subject: Re: [PATCH -v2] ext4: allow directory holes
On Jul 2, 2019, at 3:11 PM, Theodore Ts'o <tytso@....edu> wrote:
>
> The largedir feature was intended to allow ext4 directories to have
> unmapped directory blocks (e.g., directory holes). And so the
> released e2fsprogs no longer enforces this for largedir file systems;
> however, the corresponding change to the kernel-side code was not made.
>
> This commit fixes this oversight.
>
> Signed-off-by: Theodore Ts'o <tytso@....edu>
Reviewed-by: Andreas Dilger <adilger@...ger.ca>
> Cc: stable@...nel.org
> ---
> fs/ext4/dir.c | 19 +++++++++----------
> fs/ext4/namei.c | 45 +++++++++++++++++++++++++++++++++++++--------
> 2 files changed, 46 insertions(+), 18 deletions(-)
>
> diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
> index 770a1e6d4672..3a77b7affd09 100644
> --- a/fs/ext4/dir.c
> +++ b/fs/ext4/dir.c
> @@ -112,7 +112,6 @@ static int ext4_readdir(struct file *file, struct dir_context *ctx)
> struct inode *inode = file_inode(file);
> struct super_block *sb = inode->i_sb;
> struct buffer_head *bh = NULL;
> - int dir_has_error = 0;
> struct fscrypt_str fstr = FSTR_INIT(NULL, 0);
>
> if (IS_ENCRYPTED(inode)) {
> @@ -148,8 +147,6 @@ static int ext4_readdir(struct file *file, struct dir_context *ctx)
> return err;
> }
>
> - offset = ctx->pos & (sb->s_blocksize - 1);
> -
> while (ctx->pos < inode->i_size) {
> struct ext4_map_blocks map;
>
> @@ -158,9 +155,18 @@ static int ext4_readdir(struct file *file, struct dir_context *ctx)
> goto errout;
> }
> cond_resched();
> + offset = ctx->pos & (sb->s_blocksize - 1);
> map.m_lblk = ctx->pos >> EXT4_BLOCK_SIZE_BITS(sb);
> map.m_len = 1;
> err = ext4_map_blocks(NULL, inode, &map, 0);
> + if (err == 0) {
> + /* m_len should never be zero but let's avoid
> + * an infinite loop if it somehow is */
> + if (map.m_len == 0)
> + map.m_len = 1;
> + ctx->pos += map.m_len * sb->s_blocksize;
> + continue;
> + }
> if (err > 0) {
> pgoff_t index = map.m_pblk >>
> (PAGE_SHIFT - inode->i_blkbits);
> @@ -179,13 +185,6 @@ static int ext4_readdir(struct file *file, struct dir_context *ctx)
> }
>
> if (!bh) {
> - if (!dir_has_error) {
> - EXT4_ERROR_FILE(file, 0,
> - "directory contains a "
> - "hole at offset %llu",
> - (unsigned long long) ctx->pos);
> - dir_has_error = 1;
> - }
> /* corrupt size? Maybe no more blocks to read */
> if (ctx->pos > inode->i_blocks << 9)
> break;
> diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
> index 4909ced4e672..0cda080f3fd5 100644
> --- a/fs/ext4/namei.c
> +++ b/fs/ext4/namei.c
> @@ -82,8 +82,18 @@ static struct buffer_head *ext4_append(handle_t *handle,
> static int ext4_dx_csum_verify(struct inode *inode,
> struct ext4_dir_entry *dirent);
>
> +/*
> + * Hints to ext4_read_dirblock regarding whether we expect a directory
> + * block being read to be an index block, or a block containing
> + * directory entries (and if the latter, whether it was found via a
> + * logical block in an htree index block). This is used to control
> + * what sort of sanity checkinig ext4_read_dirblock() will do on the
> + * directory block read from the storage device. EITHER will means
> + * the caller doesn't know what kind of directory block will be read,
> + * so no specific verification will be done.
> + */
> typedef enum {
> - EITHER, INDEX, DIRENT
> + EITHER, INDEX, DIRENT, DIRENT_HTREE
> } dirblock_type_t;
>
> #define ext4_read_dirblock(inode, block, type) \
> @@ -109,11 +119,14 @@ static struct buffer_head *__ext4_read_dirblock(struct inode *inode,
>
> return bh;
> }
> - if (!bh) {
> + if (!bh && (type == INDEX || type == DIRENT_HTREE)) {
> ext4_error_inode(inode, func, line, block,
> - "Directory hole found");
> + "Directory hole found for htree %s block",
> + (type == INDEX) ? "index" : "leaf");
> return ERR_PTR(-EFSCORRUPTED);
> }
> + if (!bh)
> + return NULL;
> dirent = (struct ext4_dir_entry *) bh->b_data;
> /* Determine whether or not we have an index block */
> if (is_dx(inode)) {
> @@ -980,7 +993,7 @@ static int htree_dirblock_to_tree(struct file *dir_file,
>
> dxtrace(printk(KERN_INFO "In htree dirblock_to_tree: block %lu\n",
> (unsigned long)block));
> - bh = ext4_read_dirblock(dir, block, DIRENT);
> + bh = ext4_read_dirblock(dir, block, DIRENT_HTREE);
> if (IS_ERR(bh))
> return PTR_ERR(bh);
>
> @@ -1619,7 +1632,7 @@ static struct buffer_head * ext4_dx_find_entry(struct inode *dir,
> return (struct buffer_head *) frame;
> do {
> block = dx_get_block(frame->at);
> - bh = ext4_read_dirblock(dir, block, DIRENT);
> + bh = ext4_read_dirblock(dir, block, DIRENT_HTREE);
> if (IS_ERR(bh))
> goto errout;
>
> @@ -2203,6 +2216,11 @@ static int ext4_add_entry(handle_t *handle, struct dentry *dentry,
> blocks = dir->i_size >> sb->s_blocksize_bits;
> for (block = 0; block < blocks; block++) {
> bh = ext4_read_dirblock(dir, block, DIRENT);
> + if (bh == NULL) {
> + bh = ext4_bread(handle, dir, block,
> + EXT4_GET_BLOCKS_CREATE);
> + goto add_to_new_block;
> + }
> if (IS_ERR(bh)) {
> retval = PTR_ERR(bh);
> bh = NULL;
> @@ -2223,6 +2241,7 @@ static int ext4_add_entry(handle_t *handle, struct dentry *dentry,
> brelse(bh);
> }
> bh = ext4_append(handle, dir, &block);
> +add_to_new_block:
> if (IS_ERR(bh)) {
> retval = PTR_ERR(bh);
> bh = NULL;
> @@ -2267,7 +2286,7 @@ static int ext4_dx_add_entry(handle_t *handle, struct ext4_filename *fname,
> return PTR_ERR(frame);
> entries = frame->entries;
> at = frame->at;
> - bh = ext4_read_dirblock(dir, dx_get_block(frame->at), DIRENT);
> + bh = ext4_read_dirblock(dir, dx_get_block(frame->at), DIRENT_HTREE);
> if (IS_ERR(bh)) {
> err = PTR_ERR(bh);
> bh = NULL;
> @@ -2815,7 +2834,10 @@ bool ext4_empty_dir(struct inode *inode)
> EXT4_ERROR_INODE(inode, "invalid size");
> return true;
> }
> - bh = ext4_read_dirblock(inode, 0, EITHER);
> + /* The first directory block must not be a hole,
> + * so treat it as DIRENT_HTREE
> + */
> + bh = ext4_read_dirblock(inode, 0, DIRENT_HTREE);
> if (IS_ERR(bh))
> return true;
>
> @@ -2837,6 +2859,10 @@ bool ext4_empty_dir(struct inode *inode)
> brelse(bh);
> lblock = offset >> EXT4_BLOCK_SIZE_BITS(sb);
> bh = ext4_read_dirblock(inode, lblock, EITHER);
> + if (bh == NULL) {
> + offset += sb->s_blocksize;
> + continue;
> + }
> if (IS_ERR(bh))
> return true;
> de = (struct ext4_dir_entry_2 *) bh->b_data;
> @@ -3402,7 +3428,10 @@ static struct buffer_head *ext4_get_first_dir_block(handle_t *handle,
> struct buffer_head *bh;
>
> if (!ext4_has_inline_data(inode)) {
> - bh = ext4_read_dirblock(inode, 0, EITHER);
> + /* The first directory block must not be a hole, so
> + * treat it as DIRENT_HTREE
> + */
> + bh = ext4_read_dirblock(inode, 0, DIRENT_HTREE);
> if (IS_ERR(bh)) {
> *retval = PTR_ERR(bh);
> return NULL;
> --
> 2.22.0
>
Cheers, Andreas
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