ext4: Fix bugs in mballoc's stream allocation mode

(cherry picked from commit 4ba74d00a20256e22f159cb288ff34b587608917)

The logic around sbi->s_mb_last_group and sbi->s_mb_last_start was all
screwed up.  These fields were getting unconditionally all the time,
set even when stream allocation had not taken place, and if they were
being used when the file was smaller than s_mb_stream_request, which
is when the allocation should _not_ be doing stream allocation.

Fix this by determining whether or not we stream allocation should
take place once, in ext4_mb_group_or_file(), and setting a flag which
gets used in ext4_mb_regular_allocator() and ext4_mb_use_best_found().
This simplifies the code and assures that we are consistently using
(or not using) the stream allocation logic.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 9714db393efe8a1b6fa2ff0b2e7cf36fb7ecc199..d95ed85828652bbe49dd1b349a1d40a7073181cf 100644 (file)
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -88,6 +88,8 @@ typedef unsigned int ext4_group_t;
 #define EXT4_MB_HINT_TRY_GOAL          512
 /* blocks already pre-reserved by delayed allocation */
 #define EXT4_MB_DELALLOC_RESERVED      1024
+/* We are doing stream allocation */
+#define EXT4_MB_STREAM_ALLOC           2048
 
 
 struct ext4_allocation_request {

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index cf9972090ad9ffa2a0cb8f35d4e41c5a5031f03a..3e8fde1aa11afd9fc5a0b84208dccaf33e2ba4b9 100644 (file)
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -1360,7 +1360,7 @@ static void ext4_mb_use_best_found(struct ext4_allocation_context *ac,
        ac->alloc_semp =  e4b->alloc_semp;
        e4b->alloc_semp = NULL;
        /* store last allocated for subsequent stream allocation */
-       if ((ac->ac_flags & EXT4_MB_HINT_DATA)) {
+       if (ac->ac_flags & EXT4_MB_STREAM_ALLOC) {
                spin_lock(&sbi->s_md_lock);
                sbi->s_mb_last_group = ac->ac_f_ex.fe_group;
                sbi->s_mb_last_start = ac->ac_f_ex.fe_start;
@@ -1938,7 +1938,6 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
        struct ext4_sb_info *sbi;
        struct super_block *sb;
        struct ext4_buddy e4b;
-       loff_t size, isize;
 
        sb = ac->ac_sb;
        sbi = EXT4_SB(sb);
@@ -1974,20 +1973,16 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
        }
 
        bsbits = ac->ac_sb->s_blocksize_bits;
-       /* if stream allocation is enabled, use global goal */
-       size = ac->ac_o_ex.fe_logical + ac->ac_o_ex.fe_len;
-       isize = i_size_read(ac->ac_inode) >> bsbits;
-       if (size < isize)
-               size = isize;
 
-       if (size < sbi->s_mb_stream_request &&
-                       (ac->ac_flags & EXT4_MB_HINT_DATA)) {
+       /* if stream allocation is enabled, use global goal */
+       if (ac->ac_flags & EXT4_MB_STREAM_ALLOC) {
                /* TBD: may be hot point */
                spin_lock(&sbi->s_md_lock);
                ac->ac_g_ex.fe_group = sbi->s_mb_last_group;
                ac->ac_g_ex.fe_start = sbi->s_mb_last_start;
                spin_unlock(&sbi->s_md_lock);
        }
+
        /* Let's just scan groups to find more-less suitable blocks */
        cr = ac->ac_2order ? 0 : 1;
        /*
@@ -4155,16 +4150,18 @@ static void ext4_mb_group_or_file(struct ext4_allocation_context *ac)
        if (!(ac->ac_flags & EXT4_MB_HINT_DATA))
                return;
 
+       if (unlikely(ac->ac_flags & EXT4_MB_HINT_GOAL_ONLY))
+               return;
+
        size = ac->ac_o_ex.fe_logical + ac->ac_o_ex.fe_len;
        isize = i_size_read(ac->ac_inode) >> bsbits;
        size = max(size, isize);
 
        /* don't use group allocation for large files */
-       if (size >= sbi->s_mb_stream_request)
-               return;
-
-       if (unlikely(ac->ac_flags & EXT4_MB_HINT_GOAL_ONLY))
+       if (size >= sbi->s_mb_stream_request) {
+               ac->ac_flags |= EXT4_MB_STREAM_ALLOC;
                return;
+       }
 
        BUG_ON(ac->ac_lg != NULL);
        /*