Commit 30fac0f7 authored by Jan Kara's avatar Jan Kara Committed by Theodore Ts'o
Browse files

ext4: Do not reserve clusters when fs doesn't support extents 



When the filesystem doesn't support extents (like in ext2/3
compatibility modes), there is no need to reserve any clusters. Space
estimates for writing are exact, hole punching doesn't need new
metadata, and there are no unwritten extents to convert.

This fixes a problem when filesystem still having some free space when
accessed with a native ext2/3 driver suddently reports ENOSPC when
accessed with ext4 driver.

Reported-by: default avatarGeert Uytterhoeven <geert@linux-m68k.org>
Tested-by: default avatarGeert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: default avatarLukas Czerner <lczerner@redhat.com>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org
parent 9105bb14

fs/ext4/super.c

+13 −4
Original line number Diff line number Diff line
@@ -3316,10 +3316,18 @@ int ext4_calculate_overhead(struct super_block *sb) 
}





static ext4_fsblk_t ext4_calculate_resv_clusters(struct ext4_sb_info *sbi)

static ext4_fsblk_t ext4_calculate_resv_clusters(struct super_block *sb)

{

	ext4_fsblk_t resv_clusters;



	/*

	 * There's no need to reserve anything when we aren't using extents.

	 * The space estimates are exact, there are no unwritten extents,

	 * hole punching doesn't need new metadata... This is needed especially

	 * to keep ext2/3 backward compatibility.

	 */

	if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_EXTENTS))

		return 0;

	/*

	 * By default we reserve 2% or 4096 clusters, whichever is smaller.

	 * This should cover the situations where we can not afford to run
@@ -3328,7 +3336,8 @@ static ext4_fsblk_t ext4_calculate_resv_clusters(struct ext4_sb_info *sbi) 
	 * allocation would require 1, or 2 blocks, higher numbers are

	 * very rare.

	 */

	resv_clusters = ext4_blocks_count(sbi->s_es) >> sbi->s_cluster_bits;

	resv_clusters = ext4_blocks_count(EXT4_SB(sb)->s_es) >>

			EXT4_SB(sb)->s_cluster_bits;



	do_div(resv_clusters, 50);

	resv_clusters = min_t(ext4_fsblk_t, resv_clusters, 4096);
@@ -4071,10 +4080,10 @@ no_journal: 
			 "available");

	}



	err = ext4_reserve_clusters(sbi, ext4_calculate_resv_clusters(sbi));

	err = ext4_reserve_clusters(sbi, ext4_calculate_resv_clusters(sb));

	if (err) {

		ext4_msg(sb, KERN_ERR, "failed to reserve %llu clusters for "

			 "reserved pool", ext4_calculate_resv_clusters(sbi));

			 "reserved pool", ext4_calculate_resv_clusters(sb));

		goto failed_mount4a;

	}

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