From f702ba0fd7d50b5f5f5aea5317875a10d40b869f Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Mon, 22 Sep 2008 15:21:01 -0400 Subject: [PATCH] ext4: Don't use 'struct dentry' for internal lookups This is a port of a patch from Linus which fixes a 200+ byte stack usage problem in ext4_get_parent(). It's more efficient to pass down only the actual parts of the dentry that matter: the parent inode and the name, instead of allocating a struct dentry on the stack. Signed-off-by: Linus Torvalds Signed-off-by: "Theodore Ts'o" --- fs/ext4/namei.c | 68 ++++++++++++++++++++++++------------------------- 1 file changed, 33 insertions(+), 35 deletions(-) diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c index a1f72d217c7c..5295a9225cf9 100644 --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -159,7 +159,7 @@ static void dx_set_count(struct dx_entry *entries, unsigned value); static void dx_set_limit(struct dx_entry *entries, unsigned value); static unsigned dx_root_limit(struct inode *dir, unsigned infosize); static unsigned dx_node_limit(struct inode *dir); -static struct dx_frame *dx_probe(struct dentry *dentry, +static struct dx_frame *dx_probe(const struct qstr *d_name, struct inode *dir, struct dx_hash_info *hinfo, struct dx_frame *frame, @@ -177,8 +177,10 @@ static int ext4_htree_next_block(struct inode *dir, __u32 hash, struct dx_frame *frame, struct dx_frame *frames, __u32 *start_hash); -static struct buffer_head * ext4_dx_find_entry(struct dentry *dentry, - struct ext4_dir_entry_2 **res_dir, int *err); +static struct buffer_head * ext4_dx_find_entry(struct inode *dir, + const struct qstr *d_name, + struct ext4_dir_entry_2 **res_dir, + int *err); static int ext4_dx_add_entry(handle_t *handle, struct dentry *dentry, struct inode *inode); @@ -345,7 +347,7 @@ struct stats dx_show_entries(struct dx_hash_info *hinfo, struct inode *dir, * back to userspace. */ static struct dx_frame * -dx_probe(struct dentry *dentry, struct inode *dir, +dx_probe(const struct qstr *d_name, struct inode *dir, struct dx_hash_info *hinfo, struct dx_frame *frame_in, int *err) { unsigned count, indirect; @@ -356,8 +358,6 @@ dx_probe(struct dentry *dentry, struct inode *dir, u32 hash; frame->bh = NULL; - if (dentry) - dir = dentry->d_parent->d_inode; if (!(bh = ext4_bread (NULL,dir, 0, 0, err))) goto fail; root = (struct dx_root *) bh->b_data; @@ -373,8 +373,8 @@ dx_probe(struct dentry *dentry, struct inode *dir, } hinfo->hash_version = root->info.hash_version; hinfo->seed = EXT4_SB(dir->i_sb)->s_hash_seed; - if (dentry) - ext4fs_dirhash(dentry->d_name.name, dentry->d_name.len, hinfo); + if (d_name) + ext4fs_dirhash(d_name->name, d_name->len, hinfo); hash = hinfo->hash; if (root->info.unused_flags & 1) { @@ -649,7 +649,7 @@ int ext4_htree_fill_tree(struct file *dir_file, __u32 start_hash, } hinfo.hash = start_hash; hinfo.minor_hash = 0; - frame = dx_probe(NULL, dir_file->f_path.dentry->d_inode, &hinfo, frames, &err); + frame = dx_probe(NULL, dir, &hinfo, frames, &err); if (!frame) return err; @@ -805,15 +805,15 @@ static inline int ext4_match (int len, const char * const name, */ static inline int search_dirblock(struct buffer_head *bh, struct inode *dir, - struct dentry *dentry, + const struct qstr *d_name, unsigned long offset, struct ext4_dir_entry_2 ** res_dir) { struct ext4_dir_entry_2 * de; char * dlimit; int de_len; - const char *name = dentry->d_name.name; - int namelen = dentry->d_name.len; + const char *name = d_name->name; + int namelen = d_name->len; de = (struct ext4_dir_entry_2 *) bh->b_data; dlimit = bh->b_data + dir->i_sb->s_blocksize; @@ -852,7 +852,8 @@ static inline int search_dirblock(struct buffer_head *bh, * The returned buffer_head has ->b_count elevated. The caller is expected * to brelse() it when appropriate. */ -static struct buffer_head * ext4_find_entry (struct dentry *dentry, +static struct buffer_head * ext4_find_entry (struct inode *dir, + const struct qstr *d_name, struct ext4_dir_entry_2 ** res_dir) { struct super_block *sb; @@ -866,16 +867,15 @@ static struct buffer_head * ext4_find_entry (struct dentry *dentry, int num = 0; ext4_lblk_t nblocks; int i, err; - struct inode *dir = dentry->d_parent->d_inode; int namelen; *res_dir = NULL; sb = dir->i_sb; - namelen = dentry->d_name.len; + namelen = d_name->len; if (namelen > EXT4_NAME_LEN) return NULL; if (is_dx(dir)) { - bh = ext4_dx_find_entry(dentry, res_dir, &err); + bh = ext4_dx_find_entry(dir, d_name, res_dir, &err); /* * On success, or if the error was file not found, * return. Otherwise, fall back to doing a search the @@ -928,7 +928,7 @@ static struct buffer_head * ext4_find_entry (struct dentry *dentry, brelse(bh); goto next; } - i = search_dirblock(bh, dir, dentry, + i = search_dirblock(bh, dir, d_name, block << EXT4_BLOCK_SIZE_BITS(sb), res_dir); if (i == 1) { EXT4_I(dir)->i_dir_start_lookup = block; @@ -962,7 +962,7 @@ static struct buffer_head * ext4_find_entry (struct dentry *dentry, return ret; } -static struct buffer_head * ext4_dx_find_entry(struct dentry *dentry, +static struct buffer_head * ext4_dx_find_entry(struct inode *dir, const struct qstr *d_name, struct ext4_dir_entry_2 **res_dir, int *err) { struct super_block * sb; @@ -973,14 +973,13 @@ static struct buffer_head * ext4_dx_find_entry(struct dentry *dentry, struct buffer_head *bh; ext4_lblk_t block; int retval; - int namelen = dentry->d_name.len; - const u8 *name = dentry->d_name.name; - struct inode *dir = dentry->d_parent->d_inode; + int namelen = d_name->len; + const u8 *name = d_name->name; sb = dir->i_sb; /* NFS may look up ".." - look at dx_root directory block */ if (namelen > 2 || name[0] != '.'||(name[1] != '.' && name[1] != '\0')){ - if (!(frame = dx_probe(dentry, NULL, &hinfo, frames, err))) + if (!(frame = dx_probe(d_name, dir, &hinfo, frames, err))) return NULL; } else { frame = frames; @@ -1041,7 +1040,7 @@ static struct dentry *ext4_lookup(struct inode *dir, struct dentry *dentry, stru if (dentry->d_name.len > EXT4_NAME_LEN) return ERR_PTR(-ENAMETOOLONG); - bh = ext4_find_entry(dentry, &de); + bh = ext4_find_entry(dir, &dentry->d_name, &de); inode = NULL; if (bh) { unsigned long ino = le32_to_cpu(de->inode); @@ -1064,15 +1063,14 @@ struct dentry *ext4_get_parent(struct dentry *child) unsigned long ino; struct dentry *parent; struct inode *inode; - struct dentry dotdot; + static const struct qstr dotdot = { + .name = "..", + .len = 2, + }; struct ext4_dir_entry_2 * de; struct buffer_head *bh; - dotdot.d_name.name = ".."; - dotdot.d_name.len = 2; - dotdot.d_parent = child; /* confusing, isn't it! */ - - bh = ext4_find_entry(&dotdot, &de); + bh = ext4_find_entry(child->d_inode, &dotdot, &de); inode = NULL; if (!bh) return ERR_PTR(-ENOENT); @@ -1508,7 +1506,7 @@ static int ext4_dx_add_entry(handle_t *handle, struct dentry *dentry, struct ext4_dir_entry_2 *de; int err; - frame = dx_probe(dentry, NULL, &hinfo, frames, &err); + frame = dx_probe(&dentry->d_name, dir, &hinfo, frames, &err); if (!frame) return err; entries = frame->entries; @@ -2089,7 +2087,7 @@ static int ext4_rmdir(struct inode *dir, struct dentry *dentry) return PTR_ERR(handle); retval = -ENOENT; - bh = ext4_find_entry(dentry, &de); + bh = ext4_find_entry(dir, &dentry->d_name, &de); if (!bh) goto end_rmdir; @@ -2151,7 +2149,7 @@ static int ext4_unlink(struct inode *dir, struct dentry *dentry) handle->h_sync = 1; retval = -ENOENT; - bh = ext4_find_entry(dentry, &de); + bh = ext4_find_entry(dir, &dentry->d_name, &de); if (!bh) goto end_unlink; @@ -2312,7 +2310,7 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry, if (IS_DIRSYNC(old_dir) || IS_DIRSYNC(new_dir)) handle->h_sync = 1; - old_bh = ext4_find_entry(old_dentry, &old_de); + old_bh = ext4_find_entry(old_dir, &old_dentry->d_name, &old_de); /* * Check for inode number is _not_ due to possible IO errors. * We might rmdir the source, keep it as pwd of some process @@ -2325,7 +2323,7 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry, goto end_rename; new_inode = new_dentry->d_inode; - new_bh = ext4_find_entry(new_dentry, &new_de); + new_bh = ext4_find_entry(new_dir, &new_dentry->d_name, &new_de); if (new_bh) { if (!new_inode) { brelse(new_bh); @@ -2392,7 +2390,7 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry, struct buffer_head *old_bh2; struct ext4_dir_entry_2 *old_de2; - old_bh2 = ext4_find_entry(old_dentry, &old_de2); + old_bh2 = ext4_find_entry(old_dir, &old_dentry->d_name, &old_de2); if (old_bh2) { retval = ext4_delete_entry(handle, old_dir, old_de2, old_bh2); -- GitLab