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fat: remove cluster allocation size limit

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Patch series "fat: allocate multiple clusters in fallocate", v2.

This series adds support for allocating multiple clusters in a single
fat_add_clusters() call in fat_fallocate().

The multi-cluster TODO in inode.c is not implemented, as doing so would
require speculative preallocation or an iomap conversion.


This patch (of 3):

fat_alloc_clusters() currently BUG()s when asked to allocate more than
MAX_BUF_PER_PAGE / 2 clusters. This limit comes from the buffer_head
array used to defer syncing and mirroring.

Remove the allocation size limit by doing buffer_head batching like
fat_free_clusters() does.

Link: https://lore.kernel.org/20261012171106.146243-1-matheus.aalmeida@inf.ufrgs.br
Link: https://lore.kernel.org/20261012171106.146243-2-matheus.aalmeida@inf.ufrgs.br
Signed-off-by: Matheus Alves de Almeida <matheus.aalmeida@inf.ufrgs.br>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
This commit is contained in:
Matheus Alves de Almeida 2026-10-12 14:11:04 -03:00 committed by Andrew Morton
parent edb528227f
commit 930256458a
1 changed files with 31 additions and 13 deletions
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44
fs/fat/fatent.c
View File

@ -483,6 +483,26 @@ static void fat_collect_bhs(struct buffer_head **bhs, int *nr_bhs,
}
}
static int fat_flush_bhs(struct super_block *sb, struct buffer_head **bhs,
int *nr_bhs, bool sync)
{
int err, i;
if (sync) {
err = fat_sync_bhs(bhs, *nr_bhs);
if (err)
return err;
}
err = fat_mirror_bhs(sb, bhs, *nr_bhs);
if (err)
return err;
for (i = 0; i < *nr_bhs; i++)
brelse(bhs[i]);
*nr_bhs = 0;
return 0;
}
int fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster)
{
struct super_block *sb = inode->i_sb;
@ -492,8 +512,6 @@ int fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster)
struct buffer_head *bhs[MAX_BUF_PER_PAGE];
int i, count, err, nr_bhs, idx_clus;
BUG_ON(nr_cluster > (MAX_BUF_PER_PAGE / 2)); /* fixed limit */
lock_fat(sbi);
if (sbi->free_clusters != -1 && sbi->free_clus_valid &&
sbi->free_clusters < nr_cluster) {
@ -524,14 +542,21 @@ int fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster)
if (prev_ent.nr_bhs)
ops->ent_put(&prev_ent, entry);
fat_collect_bhs(bhs, &nr_bhs, &fatent);
sbi->prev_free = entry;
if (sbi->free_clusters != -1)
sbi->free_clusters--;
cluster[idx_clus] = entry;
idx_clus++;
if (nr_bhs + fatent.nr_bhs > MAX_BUF_PER_PAGE) {
err = fat_flush_bhs(sb, bhs, &nr_bhs,
inode_needs_sync(inode));
if (err)
goto out;
}
fat_collect_bhs(bhs, &nr_bhs, &fatent);
if (idx_clus == nr_cluster)
goto out;
@ -621,17 +646,10 @@ int fat_free_clusters(struct inode *inode, int cluster)
}
if (nr_bhs + fatent.nr_bhs > MAX_BUF_PER_PAGE) {
if (sb->s_flags & SB_SYNCHRONOUS) {
err = fat_sync_bhs(bhs, nr_bhs);
if (err)
goto error;
}
err = fat_mirror_bhs(sb, bhs, nr_bhs);
err = fat_flush_bhs(sb, bhs, &nr_bhs,
sb->s_flags & SB_SYNCHRONOUS);
if (err)
goto error;
for (i = 0; i < nr_bhs; i++)
brelse(bhs[i]);
nr_bhs = 0;
}
fat_collect_bhs(bhs, &nr_bhs, &fatent);
} while (cluster != FAT_ENT_EOF);