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2773d282cd
VFS has switched to i_rwsem for ten years now (9902af79c0: parallel
lookups actual switch to rwsem), but the VFS documentation and comments
still has references to i_mutex.
Signed-off-by: Junxuan Liao <ljx@cs.wisc.edu>
Link: https://lore.kernel.org/72223729-5471-474a-af3c-f366691fba82@cs.wisc.edu
Signed-off-by: Christian Brauner <brauner@kernel.org>
76 lines
2.6 KiB
C
76 lines
2.6 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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#include <linux/export.h>
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#include <linux/fs.h>
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#include <linux/fs_stack.h>
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/* does _NOT_ require i_rwsem to be held.
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*
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* This function cannot be inlined since i_size_{read,write} is rather
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* heavy-weight on 32-bit systems
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*/
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void fsstack_copy_inode_size(struct inode *dst, struct inode *src)
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{
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loff_t i_size;
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blkcnt_t i_blocks;
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/*
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* i_size_read() includes its own seqlocking and protection from
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* preemption (see include/linux/fs.h): we need nothing extra for
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* that here, and prefer to avoid nesting locks than attempt to keep
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* i_size and i_blocks in sync together.
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*/
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i_size = i_size_read(src);
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/*
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* But on 32-bit, we ought to make an effort to keep the two halves of
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* i_blocks in sync despite SMP or PREEMPTION - though stat's
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* generic_fillattr() doesn't bother, and we won't be applying quotas
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* (where i_blocks does become important) at the upper level.
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*
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* We don't actually know what locking is used at the lower level;
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* but if it's a filesystem that supports quotas, it will be using
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* i_lock as in inode_add_bytes().
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*/
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if (sizeof(i_blocks) > sizeof(long))
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spin_lock(&src->i_lock);
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i_blocks = src->i_blocks;
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if (sizeof(i_blocks) > sizeof(long))
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spin_unlock(&src->i_lock);
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/*
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* If CONFIG_SMP or CONFIG_PREEMPTION on 32-bit, it's vital for
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* fsstack_copy_inode_size() to hold some lock around
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* i_size_write(), otherwise i_size_read() may spin forever (see
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* include/linux/fs.h). We don't necessarily hold i_rwsem when this
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* is called, so take i_lock for that case.
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*
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* And if on 32-bit, continue our effort to keep the two halves of
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* i_blocks in sync despite SMP or PREEMPTION: use i_lock for that case
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* too, and do both at once by combining the tests.
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*
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* There is none of this locking overhead in the 64-bit case.
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*/
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if (sizeof(i_size) > sizeof(long) || sizeof(i_blocks) > sizeof(long))
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spin_lock(&dst->i_lock);
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i_size_write(dst, i_size);
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dst->i_blocks = i_blocks;
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if (sizeof(i_size) > sizeof(long) || sizeof(i_blocks) > sizeof(long))
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spin_unlock(&dst->i_lock);
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}
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EXPORT_SYMBOL_GPL(fsstack_copy_inode_size);
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/* copy all attributes */
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void fsstack_copy_attr_all(struct inode *dest, const struct inode *src)
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{
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dest->i_mode = src->i_mode;
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dest->i_uid = src->i_uid;
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dest->i_gid = src->i_gid;
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dest->i_rdev = src->i_rdev;
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inode_set_atime_to_ts(dest, inode_get_atime(src));
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inode_set_mtime_to_ts(dest, inode_get_mtime(src));
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inode_set_ctime_to_ts(dest, inode_get_ctime(src));
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dest->i_blkbits = src->i_blkbits;
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dest->i_flags = src->i_flags;
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set_nlink(dest, src->i_nlink);
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}
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EXPORT_SYMBOL_GPL(fsstack_copy_attr_all);
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