litmus-rt.git - The LITMUS^RT kernel.

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author	Artem Bityutskiy <artem.bityutskiy@linux.intel.com>	2012-07-22 20:33:31 -0400
committer	Theodore Ts'o <tytso@mit.edu>	2012-07-22 20:33:31 -0400
commit	58c5873a769987e36265d1523d2aa5bdc18f32bd (patch)
tree	14bb293c91b8da4d1e6874fe324667da4a16e799 /kernel/stacktrace.c
parent	044ce47fec90ec0f25605e87a5d72cca14568bc3 (diff)

ext4: remove unnecessary superblock dirtying

This patch changes the 'ext4_handle_dirty_super()' function which submits the superblock for I/O in the following cases: 1. When creating the first large file on a file system without EXT4_FEATURE_RO_COMPAT_LARGE_FILE feature. 2. When re-sizing the file-system. 3. When creating an xattr on a file-system without the EXT4_FEATURE_COMPAT_EXT_ATTR feature. If the file-system has journal enabled, the superblock is written via the journal. We do not modify this path. If the file-system has no journal, this function, falls back to just marking the superblock as dirty using the 's_dirt' superblock flag. This means that it delays the actual superblock I/O submission by 5 seconds (default setting). Namely, the 'sync_supers()' kernel thread will call 'ext4_write_super()' later and will actually submit the superblock for I/O. And this is the behavior this patch modifies: we stop using 's_dirt' and just mark the superblock buffer as dirty right away. Indeed, all 3 cases above are extremely rare and it does not add any value to delay the I/O submission for them. Note: 'ext4_handle_dirty_super()' executes '__ext4_handle_dirty_super()' with 'now = 0'. This patch basically makes the 'now' argument unneeded and it will be deleted in one of the next patches. This patch also removes 's_dirt' condition on the unmount path because we never set it anymore, so we should not test it. Tested using xfstests for both journalled and non-journalled ext4. Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Reviewed-by: Jan Kara <jack@suse.cz>

Diffstat (limited to 'kernel/stacktrace.c')

0 files changed, 0 insertions, 0 deletions

/* * Cryptographic API. * * SHA1 Secure Hash Algorithm. * * Derived from cryptoapi implementation, adapted for in-place * scatterlist interface. * * Copyright (c) Alan Smithee. * Copyright (c) Andrew McDonald <andrew@mcdonald.org.uk> * Copyright (c) Jean-Francois Dive <jef@linuxbe.org> * * This program is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License as published by the Free * Software Foundation; either version 2 of the License, or (at your option) * any later version. * */ #include <crypto/internal/hash.h> #include <linux/init.h> #include <linux/module.h> #include <linux/mm.h> #include <linux/cryptohash.h> #include <linux/types.h> #include <crypto/sha.h> #include <asm/byteorder.h> static int sha1_init(struct shash_desc *desc) { struct sha1_state *sctx = shash_desc_ctx(desc); *sctx = (struct sha1_state){ .state = { SHA1_H0, SHA1_H1, SHA1_H2, SHA1_H3, SHA1_H4 }, }; return 0; } int crypto_sha1_update(struct shash_desc *desc, const u8 *data, unsigned int len) { struct sha1_state *sctx = shash_desc_ctx(desc); unsigned int partial, done; const u8 *src; partial = sctx->count % SHA1_BLOCK_SIZE; sctx->count += len; done = 0; src = data; if ((partial + len) >= SHA1_BLOCK_SIZE) { u32 temp[SHA_WORKSPACE_WORDS]; if (partial) { done = -partial; memcpy(sctx->buffer + partial, data, done + SHA1_BLOCK_SIZE); src = sctx->buffer; } do { sha_transform(sctx->state, src, temp); done += SHA1_BLOCK_SIZE; src = data + done; } while (done + SHA1_BLOCK_SIZE <= len); memset(temp, 0, sizeof(temp)); partial = 0; } memcpy(sctx->buffer + partial, src, len - done); return 0; } EXPORT_SYMBOL(crypto_sha1_update); /* Add padding and return the message digest. */ static int sha1_final(struct shash_desc *desc, u8 *out) { struct sha1_state *sctx = shash_desc_ctx(desc); __be32 *dst = (__be32 *)out; u32 i, index, padlen; __be64 bits; static const u8 padding[64] = { 0x80, }; bits = cpu_to_be64(sctx->count << 3); /* Pad out to 56 mod 64 */ index = sctx->count & 0x3f; padlen = (index < 56) ? (56 - index) : ((64+56) - index); crypto_sha1_update(desc, padding, padlen); /* Append length */ crypto_sha1_update(desc, (const u8 *)&bits, sizeof(bits)); /* Store state in digest */ for (i = 0; i < 5; i++) dst[i] = cpu_to_be32(sctx->state[i]); /* Wipe context */ memset(sctx, 0, sizeof *sctx); return 0; } static int sha1_export(struct shash_desc *desc, void *out) { struct sha1_state *sctx = shash_desc_ctx(desc); memcpy(out, sctx, sizeof(*sctx)); return 0; } static int sha1_import(struct shash_desc *desc, const void *in) { struct sha1_state *sctx = shash_desc_ctx(desc); memcpy(sctx, in, sizeof(*sctx)); return 0; } static struct shash_alg alg = { .digestsize = SHA1_DIGEST_SIZE, .init = sha1_init, .update = crypto_sha1_update, .final = sha1_final, .export = sha1_export, .import = sha1_import, .descsize = sizeof(struct sha1_state), .statesize = sizeof(struct sha1_state), .base = { .cra_name = "sha1", .cra_driver_name= "sha1-generic", .cra_flags = CRYPTO_ALG_TYPE_SHASH, .cra_blocksize = SHA1_BLOCK_SIZE, .cra_module = THIS_MODULE, } }; static int __init sha1_generic_mod_init(void) { return crypto_register_shash(&alg); } static void __exit sha1_generic_mod_fini(void) { crypto_unregister_shash(&alg); } module_init(sha1_generic_mod_init); module_exit(sha1_generic_mod_fini); MODULE_LICENSE("GPL"); MODULE_DESCRIPTION("SHA1 Secure Hash Algorithm"); MODULE_ALIAS("sha1");


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