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Commit ace01050 authored by David Sterba's avatar David Sterba Committed by Josef Bacik
Browse files

btrfs: send: lower memory requirements in common case 



The fs_path structure uses an inline buffer and falls back to a chain of
allocations, but vmalloc is not necessary because PATH_MAX fits into
PAGE_SIZE.

The size of fs_path has been reduced to 256 bytes from PAGE_SIZE,
usually 4k. Experimental measurements show that most paths on a single
filesystem do not exceed 200 bytes, and these get stored into the inline
buffer directly, which is now 230 bytes. Longer paths are kmalloced when
needed.

Signed-off-by: default avatarDavid Sterba <dsterba@suse.cz>
Signed-off-by: default avatarJosef Bacik <jbacik@fb.com>
parent dff6d0ad

fs/btrfs/send.c

+37 −69
Original line number Diff line number Diff line
@@ -57,7 +57,12 @@ struct fs_path { 
			unsigned short reversed:1;

			char inline_buf[];

		};

		char pad[PAGE_SIZE];

		/*

		 * Average path length does not exceed 200 bytes, we'll have

		 * better packing in the slab and higher chance to satisfy

		 * a allocation later during send.

		 */

		char pad[256];

	};

};

#define FS_PATH_INLINE_SIZE \
@@ -262,12 +267,8 @@ static void fs_path_free(struct fs_path *p) 
{

	if (!p)

		return;

	if (p->buf != p->inline_buf) {

		if (is_vmalloc_addr(p->buf))

			vfree(p->buf);

		else

	if (p->buf != p->inline_buf)

		kfree(p->buf);

	}

	kfree(p);

}
@@ -287,40 +288,31 @@ static int fs_path_ensure_buf(struct fs_path *p, int len) 
	if (p->buf_len >= len)

		return 0;



	path_len = p->end - p->start;

	old_buf_len = p->buf_len;

	len = PAGE_ALIGN(len);



	/*

	 * First time the inline_buf does not suffice

	 */

	if (p->buf == p->inline_buf) {

		tmp_buf = kmalloc(len, GFP_NOFS | __GFP_NOWARN);

		if (!tmp_buf) {

			tmp_buf = vmalloc(len);

			if (!tmp_buf)

		p->buf = kmalloc(len, GFP_NOFS);

		if (!p->buf)

			return -ENOMEM;

		}

		memcpy(tmp_buf, p->buf, p->buf_len);

		p->buf = tmp_buf;

		p->buf_len = len;

	} else {

		if (is_vmalloc_addr(p->buf)) {

			tmp_buf = vmalloc(len);

			if (!tmp_buf)

				return -ENOMEM;

			memcpy(tmp_buf, p->buf, p->buf_len);

			vfree(p->buf);

		/*

		 * The real size of the buffer is bigger, this will let the

		 * fast path happen most of the time

		 */

		p->buf_len = ksize(p->buf);

	} else {

			tmp_buf = krealloc(p->buf, len, GFP_NOFS);

			if (!tmp_buf) {

				tmp_buf = vmalloc(len);

				if (!tmp_buf)

		char *tmp;



		tmp = krealloc(p->buf, len, GFP_NOFS);

		if (!tmp)

			return -ENOMEM;

				memcpy(tmp_buf, p->buf, p->buf_len);

				kfree(p->buf);

			}

		}

		p->buf = tmp_buf;

		p->buf_len = len;

		p->buf = tmp;

		p->buf_len = ksize(p->buf);

	}



	path_len = p->end - p->start;

	old_buf_len = p->buf_len;



	if (p->reversed) {

		tmp_buf = p->buf + old_buf_len - path_len - 1;

		p->end = p->buf + p->buf_len - 1;
@@ -911,9 +903,7 @@ static int iterate_dir_item(struct btrfs_root *root, struct btrfs_path *path, 
	struct btrfs_dir_item *di;

	struct btrfs_key di_key;

	char *buf = NULL;

	char *buf2 = NULL;

	int buf_len;

	int buf_virtual = 0;

	const int buf_len = PATH_MAX;

	u32 name_len;

	u32 data_len;

	u32 cur;
@@ -923,7 +913,6 @@ static int iterate_dir_item(struct btrfs_root *root, struct btrfs_path *path, 
	int num;

	u8 type;



	buf_len = PAGE_SIZE;

	buf = kmalloc(buf_len, GFP_NOFS);

	if (!buf) {

		ret = -ENOMEM;
@@ -945,31 +934,13 @@ static int iterate_dir_item(struct btrfs_root *root, struct btrfs_path *path, 
		type = btrfs_dir_type(eb, di);

		btrfs_dir_item_key_to_cpu(eb, di, &di_key);



		/*

		 * Path too long

		 */

		if (name_len + data_len > buf_len) {

			buf_len = PAGE_ALIGN(name_len + data_len);

			if (buf_virtual) {

				buf2 = vmalloc(buf_len);

				if (!buf2) {

					ret = -ENOMEM;

					goto out;

				}

				vfree(buf);

			} else {

				buf2 = krealloc(buf, buf_len, GFP_NOFS);

				if (!buf2) {

					buf2 = vmalloc(buf_len);

					if (!buf2) {

						ret = -ENOMEM;

			ret = -ENAMETOOLONG;

			goto out;

		}

					kfree(buf);

					buf_virtual = 1;

				}

			}



			buf = buf2;

			buf2 = NULL;

		}



		read_extent_buffer(eb, buf, (unsigned long)(di + 1),

				name_len + data_len);
@@ -991,9 +962,6 @@ static int iterate_dir_item(struct btrfs_root *root, struct btrfs_path *path, 
	}



out:

	if (buf_virtual)

		vfree(buf);

	else

	kfree(buf);

	return ret;

}