From ace0105076a493c04e6d5e91e6a19f222d6b3875 Mon Sep 17 00:00:00 2001 From: David Sterba Date: Wed, 5 Feb 2014 16:17:34 +0100 Subject: [PATCH] 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: David Sterba Signed-off-by: Josef Bacik --- fs/btrfs/send.c | 106 +++++++++++++++++------------------------------- 1 file changed, 37 insertions(+), 69 deletions(-) diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c index a2621e7aaa5..a5da82f4912 100644 --- a/fs/btrfs/send.c +++ b/fs/btrfs/send.c @@ -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 - kfree(p->buf); - } + 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) - return -ENOMEM; - } - memcpy(tmp_buf, p->buf, p->buf_len); - p->buf = tmp_buf; - p->buf_len = len; + p->buf = kmalloc(len, GFP_NOFS); + if (!p->buf) + return -ENOMEM; + /* + * 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 { - 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); - } else { - tmp_buf = krealloc(p->buf, len, GFP_NOFS); - if (!tmp_buf) { - tmp_buf = vmalloc(len); - if (!tmp_buf) - return -ENOMEM; - memcpy(tmp_buf, p->buf, p->buf_len); - kfree(p->buf); - } - } - p->buf = tmp_buf; - p->buf_len = len; + char *tmp; + + tmp = krealloc(p->buf, len, GFP_NOFS); + if (!tmp) + return -ENOMEM; + 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; @@ -945,30 +934,12 @@ 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; - goto out; - } - kfree(buf); - buf_virtual = 1; - } - } - - buf = buf2; - buf2 = NULL; + ret = -ENAMETOOLONG; + goto out; } read_extent_buffer(eb, buf, (unsigned long)(di + 1), @@ -991,10 +962,7 @@ static int iterate_dir_item(struct btrfs_root *root, struct btrfs_path *path, } out: - if (buf_virtual) - vfree(buf); - else - kfree(buf); + kfree(buf); return ret; } -- 2.41.0