ext4: Make sure all the block allocation paths reserve blocks

commit a30d542a0035b886ffaafd0057ced0a2b28c3a4f upstream.

With delayed allocation we need to make sure block are reserved before
we attempt to allocate them. Otherwise we get block allocation failure
(ENOSPC) during writepages which cannot be handled. This would mean
silent data loss (We do a printk stating data will be lost). This patch
updates the DIO and fallocate code path to do block reservation before
block allocation. This is needed to make sure parallel DIO and fallocate
request doesn't take block out of delayed reserve space.

When free blocks count go below a threshold we switch to a slow patch
which looks at other CPU's accumulated percpu counter values.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Jayson R. King <dev@jaysonking.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index 344ec1ca8aeb32d1e7f177478ff33685916a5c92..1c0edd85dcca3b9a241899e245e504e86fbda261 100644 (file)
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -1754,6 +1754,32 @@ out:
        return ret;
 }
 
+int ext4_claim_free_blocks(struct ext4_sb_info *sbi,
+                                               ext4_fsblk_t nblocks)
+{
+       s64 free_blocks;
+       ext4_fsblk_t root_blocks = 0;
+       struct percpu_counter *fbc = &sbi->s_freeblocks_counter;
+
+       free_blocks = percpu_counter_read(fbc);
+
+       if (!capable(CAP_SYS_RESOURCE) &&
+               sbi->s_resuid != current->fsuid &&
+               (sbi->s_resgid == 0 || !in_group_p(sbi->s_resgid)))
+               root_blocks = ext4_r_blocks_count(sbi->s_es);
+
+       if (free_blocks - (nblocks + root_blocks) < EXT4_FREEBLOCKS_WATERMARK)
+               free_blocks = percpu_counter_sum(&sbi->s_freeblocks_counter);
+
+       if (free_blocks < (root_blocks + nblocks))
+               /* we don't have free space */
+               return -ENOSPC;
+
+       /* reduce fs free blocks counter */
+       percpu_counter_sub(fbc, nblocks);
+       return 0;
+}
+
 /**
  * ext4_has_free_blocks()
  * @sbi:       in-core super block structure.
@@ -1775,18 +1801,17 @@ ext4_fsblk_t ext4_has_free_blocks(struct ext4_sb_info *sbi,
                sbi->s_resuid != current->fsuid &&
                (sbi->s_resgid == 0 || !in_group_p(sbi->s_resgid)))
                root_blocks = ext4_r_blocks_count(sbi->s_es);
-#ifdef CONFIG_SMP
-       if (free_blocks - root_blocks < FBC_BATCH)
-               free_blocks =
-                       percpu_counter_sum(&sbi->s_freeblocks_counter);
-#endif
+
+       if (free_blocks - (nblocks + root_blocks) < EXT4_FREEBLOCKS_WATERMARK)
+               free_blocks = percpu_counter_sum_positive(&sbi->s_freeblocks_counter);
+
        if (free_blocks <= root_blocks)
                /* we don't have free space */
                return 0;
        if (free_blocks - root_blocks < nblocks)
                return free_blocks - root_blocks;
        return nblocks;
- }
+}
 
 
 /**
@@ -1865,14 +1890,11 @@ ext4_fsblk_t ext4_old_new_blocks(handle_t *handle, struct inode *inode,
                /*
                 * With delalloc we already reserved the blocks
                 */
-               *count = ext4_has_free_blocks(sbi, *count);
-       }
-       if (*count == 0) {
-               *errp = -ENOSPC;
-               return 0;       /*return with ENOSPC error */
+               if (ext4_claim_free_blocks(sbi, *count)) {
+                       *errp = -ENOSPC;
+                       return 0;       /*return with ENOSPC error */
+               }
        }
-       num = *count;
-
        /*
         * Check quota for allocation of this block.
         */
@@ -2067,9 +2089,13 @@ allocated:
        le16_add_cpu(&gdp->bg_free_blocks_count, -num);
        gdp->bg_checksum = ext4_group_desc_csum(sbi, group_no, gdp);
        spin_unlock(sb_bgl_lock(sbi, group_no));
-       if (!EXT4_I(inode)->i_delalloc_reserved_flag)
-               percpu_counter_sub(&sbi->s_freeblocks_counter, num);
-
+       if (!EXT4_I(inode)->i_delalloc_reserved_flag && (*count != num)) {
+               /*
+                * we allocated less blocks than we
+                * claimed. Add the difference back.
+                */
+               percpu_counter_add(&sbi->s_freeblocks_counter, *count - num);
+       }
        if (sbi->s_log_groups_per_flex) {
                ext4_group_t flex_group = ext4_flex_group(sbi, group_no);
                spin_lock(sb_bgl_lock(sbi, flex_group));

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 19857211f977f41e17f3182b23dc27a7861ceac1..7b666b2b014788a767c7accecaaae58ac87d42da 100644 (file)
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1015,6 +1015,8 @@ extern ext4_fsblk_t ext4_new_blocks(handle_t *handle, struct inode *inode,
                                        unsigned long *count, int *errp);
 extern ext4_fsblk_t ext4_old_new_blocks(handle_t *handle, struct inode *inode,
                        ext4_fsblk_t goal, unsigned long *count, int *errp);
+extern int ext4_claim_free_blocks(struct ext4_sb_info *sbi,
+                                               ext4_fsblk_t nblocks);
 extern ext4_fsblk_t ext4_has_free_blocks(struct ext4_sb_info *sbi,
                                                ext4_fsblk_t nblocks);
 extern void ext4_free_blocks (handle_t *handle, struct inode *inode,
@@ -1245,6 +1247,17 @@ do {                                                             \
                __ext4_std_error((sb), __func__, (errno));      \
 } while (0)
 
+#ifdef CONFIG_SMP
+/* Each CPU can accumulate FBC_BATCH blocks in their local
+ * counters. So we need to make sure we have free blocks more
+ * than FBC_BATCH  * nr_cpu_ids. Also add a window of 4 times.
+ */
+#define EXT4_FREEBLOCKS_WATERMARK (4 * (FBC_BATCH * nr_cpu_ids))
+#else
+#define EXT4_FREEBLOCKS_WATERMARK 0
+#endif
+
+
 /*
  * Inodes and files operations
  */

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index ebd83cd65d151578c983eab7075120c7d8dd097b..7a1d2e590cb410d05a9e6b082db6711f0a46cdd7 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1564,13 +1564,10 @@ static int ext4_da_reserve_space(struct inode *inode, int nrblocks)
        md_needed = mdblocks - EXT4_I(inode)->i_reserved_meta_blocks;
        total = md_needed + nrblocks;
 
-       if (ext4_has_free_blocks(sbi, total) < total) {
+       if (ext4_claim_free_blocks(sbi, total)) {
                spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
                return -ENOSPC;
        }
-       /* reduce fs free blocks counter */
-       percpu_counter_sub(&sbi->s_freeblocks_counter, total);
-
        EXT4_I(inode)->i_reserved_data_blocks += nrblocks;
        EXT4_I(inode)->i_reserved_meta_blocks = mdblocks;
 

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index c7dc1157c1b1b3d926cb0ad1f08958457e945c83..d9bff44be24498e8597cf22ba36a51d3484aae1b 100644 (file)
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -3194,9 +3194,15 @@ ext4_mb_mark_diskspace_used(struct ext4_allocation_context *ac,
         * at write_begin() time for delayed allocation
         * do not double accounting
         */
-       if (!(ac->ac_flags & EXT4_MB_DELALLOC_RESERVED))
-               percpu_counter_sub(&sbi->s_freeblocks_counter,
-                                       ac->ac_b_ex.fe_len);
+       if (!(ac->ac_flags & EXT4_MB_DELALLOC_RESERVED) &&
+                       ac->ac_o_ex.fe_len != ac->ac_b_ex.fe_len) {
+               /*
+                * we allocated less blocks than we calimed
+                * Add the difference back
+                */
+               percpu_counter_add(&sbi->s_freeblocks_counter,
+                               ac->ac_o_ex.fe_len - ac->ac_b_ex.fe_len);
+       }
 
        if (sbi->s_log_groups_per_flex) {
                ext4_group_t flex_group = ext4_flex_group(sbi,
@@ -4649,14 +4655,11 @@ ext4_fsblk_t ext4_mb_new_blocks(handle_t *handle,
                /*
                 * With delalloc we already reserved the blocks
                 */
-               ar->len = ext4_has_free_blocks(sbi, ar->len);
-       }
-
-       if (ar->len == 0) {
-               *errp = -ENOSPC;
-               return 0;
+               if (ext4_claim_free_blocks(sbi, ar->len)) {
+                       *errp = -ENOSPC;
+                       return 0;
+               }
        }
-
        while (ar->len && DQUOT_ALLOC_BLOCK(ar->inode, ar->len)) {
                ar->flags |= EXT4_MB_HINT_NOPREALLOC;
                ar->len--;