Re: [PATCH] Btrfs: send, lower mem requirements for processing xattrs

* Re: [PATCH] Btrfs: send, lower mem requirements for processing xattrs
  2014-08-11  0:25 [PATCH] Btrfs: send, lower mem requirements for processing xattrs Filipe Manana
@ 2014-08-10 23:52 ` Josef Bacik
  2014-08-11  0:10   ` Filipe David Manana
  2014-08-20 14:28   ` David Sterba
  2014-08-11  1:22 ` [PATCH v2] " Filipe Manana
                   ` (3 subsequent siblings)
  4 siblings, 2 replies; 10+ messages in thread
From: Josef Bacik @ 2014-08-10 23:52 UTC (permalink / raw)
  To: Filipe Manana; +Cc: linux-btrfs, lists

Sigh I can only top post from my phone.  Instead of using contig_bug just use is_vmalloc_addr.  Thanks,

Josef

Filipe Manana <fdmanana@suse.com> wrote:


Maximum xattr size can be up to nearly the leaf size. For an fs with a
leaf size larger than the page size, using kmalloc requires allocating
multiple pages that are contiguous, which might not be possible if
there's heavy memory fragmentation. Therefore fallback to vmalloc if
we fail to allocate with kmalloc. Also start with a smaller buffer size,
since xattr values typically are smaller than a page.

Reported-by: Chris Murphy <lists@colorremedies.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
---
 fs/btrfs/send.c | 41 +++++++++++++++++++++++++++++++++--------
 1 file changed, 33 insertions(+), 8 deletions(-)

diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 3c63b29..215064d 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -997,6 +997,7 @@ static int iterate_dir_item(struct btrfs_root *root, struct btrfs_path *path,
        struct btrfs_key di_key;
        char *buf = NULL;
        int buf_len;
+       bool contig_buf;
        u32 name_len;
        u32 data_len;
        u32 cur;
@@ -1006,11 +1007,13 @@ static int iterate_dir_item(struct btrfs_root *root, struct btrfs_path *path,
        int num;
        u8 type;

-       if (found_key->type == BTRFS_XATTR_ITEM_KEY)
-               buf_len = BTRFS_MAX_XATTR_SIZE(root);
-       else
-               buf_len = PATH_MAX;
-
+       /*
+        * Start with a small buffer (1 page). If later we end up needing more
+        * space, which can happen for xattrs on a fs with a leaf size > 4Kb,
+        * attempt to increase the buffer. Typically xattr values are small.
+        */
+       buf_len = PATH_MAX;
+       contig_buf = true;
        buf = kmalloc(buf_len, GFP_NOFS);
        if (!buf) {
                ret = -ENOMEM;
@@ -1037,7 +1040,7 @@ static int iterate_dir_item(struct btrfs_root *root, struct btrfs_path *path,
                                ret = -ENAMETOOLONG;
                                goto out;
                        }
-                       if (name_len + data_len > buf_len) {
+                       if (name_len + data_len > BTRFS_MAX_XATTR_SIZE(root)) {
                                ret = -E2BIG;
                                goto out;
                        }
@@ -1045,12 +1048,31 @@ static int iterate_dir_item(struct btrfs_root *root, struct btrfs_path *path,
                        /*
                         * Path too long
                         */
-                       if (name_len + data_len > buf_len) {
+                       if (name_len + data_len > PATH_MAX) {
                                ret = -ENAMETOOLONG;
                                goto out;
                        }
                }

+               if (name_len + data_len > buf_len) {
+                       if (contig_buf)
+                               kfree(buf);
+                       else
+                               vfree(buf);
+                       buf = NULL;
+                       buf_len = name_len + data_len;
+                       if (contig_buf)
+                               buf = kmalloc(buf_len, GFP_NOFS);
+                       if (!buf) {
+                               buf = vmalloc(buf_len);
+                               if (!buf) {
+                                       ret = -ENOMEM;
+                                       goto out;
+                               }
+                               contig_buf = false;
+                       }
+               }
+
                read_extent_buffer(eb, buf, (unsigned long)(di + 1),
                                name_len + data_len);

@@ -1071,7 +1093,10 @@ static int iterate_dir_item(struct btrfs_root *root, struct btrfs_path *path,
        }

 out:
-       kfree(buf);
+       if (contig_buf)
+               kfree(buf);
+       else
+               vfree(buf);
        return ret;
 }

--
1.9.1

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