fallocate should be a file operation

Currently all filesystems except XFS implement fallocate asynchronously,
while XFS forced a commit.  Both of these are suboptimal - in case of O_SYNC
I/O we really want our allocation on disk, especially for the !KEEP_SIZE
case where we actually grow the file with user-visible zeroes.  On the
other hand always commiting the transaction is a bad idea for fast-path
uses of fallocate like for example in recent Samba versions.   Given
that block allocation is a data plane operation anyway change it from
an inode operation to a file operation so that we have the file structure
available that lets us check for O_SYNC.

This also includes moving the code around for a few of the filesystems,
and remove the already unnedded S_ISDIR checks given that we only wire
up fallocate for regular files.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 258 insertions, 0 deletions

diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index fca6689e12e6..7cfdcb913363 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -19,6 +19,8 @@
 #include <linux/fs.h>
 #include <linux/gfs2_ondisk.h>
 #include <linux/ext2_fs.h>
+#include <linux/falloc.h>
+#include <linux/swap.h>
 #include <linux/crc32.h>
 #include <linux/writeback.h>
 #include <asm/uaccess.h>
@@ -610,6 +612,260 @@ static ssize_t gfs2_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
         return generic_file_aio_write(iocb, iov, nr_segs, pos);
 }
 
+static void empty_write_end(struct page *page, unsigned from,
+                           unsigned to)
+{
+        struct gfs2_inode *ip = GFS2_I(page->mapping->host);
+
+        page_zero_new_buffers(page, from, to);
+        flush_dcache_page(page);
+        mark_page_accessed(page);
+
+        if (!gfs2_is_writeback(ip))
+                gfs2_page_add_databufs(ip, page, from, to);
+
+        block_commit_write(page, from, to);
+}
+
+static int write_empty_blocks(struct page *page, unsigned from, unsigned to)
+{
+        unsigned start, end, next;
+        struct buffer_head *bh, *head;
+        int error;
+
+        if (!page_has_buffers(page)) {
+                error = __block_write_begin(page, from, to - from, gfs2_block_map);
+                if (unlikely(error))
+                        return error;
+
+                empty_write_end(page, from, to);
+                return 0;
+        }
+
+        bh = head = page_buffers(page);
+        next = end = 0;
+        while (next < from) {
+                next += bh->b_size;
+                bh = bh->b_this_page;
+        }
+        start = next;
+        do {
+                next += bh->b_size;
+                if (buffer_mapped(bh)) {
+                        if (end) {
+                                error = __block_write_begin(page, start, end - start,
+                                                            gfs2_block_map);
+                                if (unlikely(error))
+                                        return error;
+                                empty_write_end(page, start, end);
+                                end = 0;
+                        }
+                        start = next;
+                }
+                else
+                        end = next;
+                bh = bh->b_this_page;
+        } while (next < to);
+
+        if (end) {
+                error = __block_write_begin(page, start, end - start, gfs2_block_map);
+                if (unlikely(error))
+                        return error;
+                empty_write_end(page, start, end);
+        }
+
+        return 0;
+}
+
+static int fallocate_chunk(struct inode *inode, loff_t offset, loff_t len,
+                           int mode)
+{
+        struct gfs2_inode *ip = GFS2_I(inode);
+        struct buffer_head *dibh;
+        int error;
+        u64 start = offset >> PAGE_CACHE_SHIFT;
+        unsigned int start_offset = offset & ~PAGE_CACHE_MASK;
+        u64 end = (offset + len - 1) >> PAGE_CACHE_SHIFT;
+        pgoff_t curr;
+        struct page *page;
+        unsigned int end_offset = (offset + len) & ~PAGE_CACHE_MASK;
+        unsigned int from, to;
+
+        if (!end_offset)
+                end_offset = PAGE_CACHE_SIZE;
+
+        error = gfs2_meta_inode_buffer(ip, &dibh);
+        if (unlikely(error))
+                goto out;
+
+        gfs2_trans_add_bh(ip->i_gl, dibh, 1);
+
+        if (gfs2_is_stuffed(ip)) {
+                error = gfs2_unstuff_dinode(ip, NULL);
+                if (unlikely(error))
+                        goto out;
+        }
+
+        curr = start;
+        offset = start << PAGE_CACHE_SHIFT;
+        from = start_offset;
+        to = PAGE_CACHE_SIZE;
+        while (curr <= end) {
+                page = grab_cache_page_write_begin(inode->i_mapping, curr,
+                                                   AOP_FLAG_NOFS);
+                if (unlikely(!page)) {
+                        error = -ENOMEM;
+                        goto out;
+                }
+
+                if (curr == end)
+                        to = end_offset;
+                error = write_empty_blocks(page, from, to);
+                if (!error && offset + to > inode->i_size &&
+                    !(mode & FALLOC_FL_KEEP_SIZE)) {
+                        i_size_write(inode, offset + to);
+                }
+                unlock_page(page);
+                page_cache_release(page);
+                if (error)
+                        goto out;
+                curr++;
+                offset += PAGE_CACHE_SIZE;
+                from = 0;
+        }
+
+        gfs2_dinode_out(ip, dibh->b_data);
+        mark_inode_dirty(inode);
+
+        brelse(dibh);
+
+out:
+        return error;
+}
+
+static void calc_max_reserv(struct gfs2_inode *ip, loff_t max, loff_t *len,
+                            unsigned int *data_blocks, unsigned int *ind_blocks)
+{
+        const struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
+        unsigned int max_blocks = ip->i_alloc->al_rgd->rd_free_clone;
+        unsigned int tmp, max_data = max_blocks - 3 * (sdp->sd_max_height - 1);
+
+        for (tmp = max_data; tmp > sdp->sd_diptrs;) {
+                tmp = DIV_ROUND_UP(tmp, sdp->sd_inptrs);
+                max_data -= tmp;
+        }
+        /* This calculation isn't the exact reverse of gfs2_write_calc_reserve,
+           so it might end up with fewer data blocks */
+        if (max_data <= *data_blocks)
+                return;
+        *data_blocks = max_data;
+        *ind_blocks = max_blocks - max_data;
+        *len = ((loff_t)max_data - 3) << sdp->sd_sb.sb_bsize_shift;
+        if (*len > max) {
+                *len = max;
+                gfs2_write_calc_reserv(ip, max, data_blocks, ind_blocks);
+        }
+}
+
+static long gfs2_fallocate(struct file *file, int mode, loff_t offset,
+                           loff_t len)
+{
+        struct inode *inode = file->f_path.dentry->d_inode;
+        struct gfs2_sbd *sdp = GFS2_SB(inode);
+        struct gfs2_inode *ip = GFS2_I(inode);
+        unsigned int data_blocks = 0, ind_blocks = 0, rblocks;
+        loff_t bytes, max_bytes;
+        struct gfs2_alloc *al;
+        int error;
+        loff_t next = (offset + len - 1) >> sdp->sd_sb.sb_bsize_shift;
+        next = (next + 1) << sdp->sd_sb.sb_bsize_shift;
+
+        /* We only support the FALLOC_FL_KEEP_SIZE mode */
+        if (mode & ~FALLOC_FL_KEEP_SIZE)
+                return -EOPNOTSUPP;
+
+        offset = (offset >> sdp->sd_sb.sb_bsize_shift) <<
+                 sdp->sd_sb.sb_bsize_shift;
+
+        len = next - offset;
+        bytes = sdp->sd_max_rg_data * sdp->sd_sb.sb_bsize / 2;
+        if (!bytes)
+                bytes = UINT_MAX;
+
+        gfs2_holder_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, &ip->i_gh);
+        error = gfs2_glock_nq(&ip->i_gh);
+        if (unlikely(error))
+                goto out_uninit;
+
+        if (!gfs2_write_alloc_required(ip, offset, len))
+                goto out_unlock;
+
+        while (len > 0) {
+                if (len < bytes)
+                        bytes = len;
+                al = gfs2_alloc_get(ip);
+                if (!al) {
+                        error = -ENOMEM;
+                        goto out_unlock;
+                }
+
+                error = gfs2_quota_lock_check(ip);
+                if (error)
+                        goto out_alloc_put;
+
+retry:
+                gfs2_write_calc_reserv(ip, bytes, &data_blocks, &ind_blocks);
+
+                al->al_requested = data_blocks + ind_blocks;
+                error = gfs2_inplace_reserve(ip);
+                if (error) {
+                        if (error == -ENOSPC && bytes > sdp->sd_sb.sb_bsize) {
+                                bytes >>= 1;
+                                goto retry;
+                        }
+                        goto out_qunlock;
+                }
+                max_bytes = bytes;
+                calc_max_reserv(ip, len, &max_bytes, &data_blocks, &ind_blocks);
+                al->al_requested = data_blocks + ind_blocks;
+
+                rblocks = RES_DINODE + ind_blocks + RES_STATFS + RES_QUOTA +
+                          RES_RG_HDR + gfs2_rg_blocks(al);
+                if (gfs2_is_jdata(ip))
+                        rblocks += data_blocks ? data_blocks : 1;
+
+                error = gfs2_trans_begin(sdp, rblocks,
+                                         PAGE_CACHE_SIZE/sdp->sd_sb.sb_bsize);
+                if (error)
+                        goto out_trans_fail;
+
+                error = fallocate_chunk(inode, offset, max_bytes, mode);
+                gfs2_trans_end(sdp);
+
+                if (error)
+                        goto out_trans_fail;
+
+                len -= max_bytes;
+                offset += max_bytes;
+                gfs2_inplace_release(ip);
+                gfs2_quota_unlock(ip);
+                gfs2_alloc_put(ip);
+        }
+        goto out_unlock;
+
+out_trans_fail:
+        gfs2_inplace_release(ip);
+out_qunlock:
+        gfs2_quota_unlock(ip);
+out_alloc_put:
+        gfs2_alloc_put(ip);
+out_unlock:
+        gfs2_glock_dq(&ip->i_gh);
+out_uninit:
+        gfs2_holder_uninit(&ip->i_gh);
+        return error;
+}
+
 #ifdef CONFIG_GFS2_FS_LOCKING_DLM
 
 /**
@@ -765,6 +1021,7 @@ const struct file_operations gfs2_file_fops = {
         .splice_read    = generic_file_splice_read,
         .splice_write   = generic_file_splice_write,
         .setlease       = gfs2_setlease,
+        .fallocate      = gfs2_fallocate,
 };
 
 const struct file_operations gfs2_dir_fops = {
@@ -794,6 +1051,7 @@ const struct file_operations gfs2_file_fops_nolock = {
         .splice_read    = generic_file_splice_read,
         .splice_write   = generic_file_splice_write,
         .setlease       = generic_setlease,
+        .fallocate      = gfs2_fallocate,
 };
 
 const struct file_operations gfs2_dir_fops_nolock = {